- Rhodium thiolate hydroformylation complexes tethered to delamellated γ-zirconium phosphate
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Rhodium thiolate complexes intercalated in crystalline γ-zirconium phosphate or tethered to SiO2-modified γ-zirconium phosphate have been synthesised. It was observed that the addition of a solution of organic silicates to a colloidal suspension of γ-zirconium phosphate yielded amorphous substrates, which displayed very high specific areas (160-650 m2 g-1). Incorporation of a mercaptocarbonyl rhodium complex resulted in a highly selective and active catalyst precursor for the hydroformylation of 1-heptene in the liquid phase. Elemental analysis and photoelectron spectroscopy of the fresh and used samples revealed that some metal leaching occurs during the reaction, this being mainly confined to the outer layers of the solid particles. This observation, together with the high selectivity towards linear aldehydes, makes SiO2-modified γ-zirconium phosphate a good support candidate for immobilised Rh catalysts. Spectroscopic data obtained from the crystalline precursor and also from the amorphous catalyst showed that the interaction between the rhodium complex and the acid support was achieved via hydrogen bonds, forming NH groups.
- Rojas,Murcia-Mascaros,Terreros,Garcia Fierro
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- Heterogeneous selective oxidation of fatty alcohols: Oxidation of 1-tetradecanol as a model substrate
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s Selective oxidation of fatty alcohols, i.e., linear long-chain alkanols, has been scarcely investigated to date, despite its potential application in high value chemical's production. We report for the first time the liquid phase heterogeneous oxidation of 1-tetradecanol, used as a model molecule for fatty alcohols, according to green chemistry principles by using a Au/CeO2-Al2O3 catalyst and O2 as oxidant at normal pressure. High selectivity to tetradecanal (ca. 80%) or to tetradecanoic acid (60-70%) are reached at medium conversion (up to 38%), depending on the reaction conditions used. Comparison with similar tests of 1-octanol oxidation shows that the increase of the carbon chain length decreases the alcohol conversion and the formation of ester, probably due to a greater steric effect.
- Corberán, Vicente Cortés,Gómez-Avilés, Almudena,Martínez-González, Susana,Ivanova, Svetlana,Domínguez, María I.,González-Pérez, María Elena
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- Rhodium nanoparticles as precursors for the preparation of an efficient and recyclable hydroformylation catalyst
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Despite all the advances in the application of nanoparticle (NP) catalysts, they have received little attention in relation to the hydroformylation reaction. Herein, we present the preparation of a hydroformylation catalyst through the immobilization of air-stable rhodium NPs onto a magnetic support functionalized with chelating phosphine ligands, which serves as an alternative to air-sensitive precursors. The catalyst was active in hydroformylation and could be used in successive reactions with negligible metal leaching. The interaction between the rhodium NPs and the diphenylphosphine ligand was evidenced by an enhancement in the Raman spectrum of the ligand. Changes occurred in the Raman spectrum of the catalyst recovered after the reaction, which suggests that the rhodium NPs are precursors of active molecular species that are formed in situ. The supported catalyst was active for successive reactions even after it was exposed to air during the recycling runs and was easily recovered through magnetic separation. Long live the catalyst! The heterogenization of rhodium catalysts onto a magnetic support and recovery without loss of metal, reactivity, and selectivity is discussed. Rhodium nanoparticles are used as catalyst precursors, and the active species are studied by using Raman spectroscopy.
- Garcia, Marco A. S.,Oliveira, Kelley C. B.,Costa, Jean C. S.,Corio, Paola,Gusevskaya, Elena V.,Dos Santos, Eduardo N.,Rossi, Liane M.
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- Coprecipitated gold-trieobalt tetraoxide catalyst for heterogeneous hydroformylation of oleflns
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The combination of gold (Au0) and tricobalt tetraoxide (CO 3O4) prepared by coprecipitation gives high-performance heterogeneous catalysts for hydroformylation reaction with selectivity above 85% in desired aldehydes, alth
- Liu, Xiaohao,Haruta, Masatake,Tokunaga, Makoto
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- XL-Xantphos: Design and Synthesis of a Mechanistic Probe of Xantphos O-Coordination in Catalytic Reactions
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The synthesis and characterization of an analog of the Xantphos ligand that is geometrically incapable of coordination of the xanthene bridging oxygen atom is reported. This new ligand, XL-Xantphos, ((9,9-dimethyl-9H-xanthene-4,5-diyl)bis(4,1-phenylene))bis(diphenylphosphane), was studied in homogeneous, catalytic reactions for comparison with Xantphos. The XL-Xantphos ligand performed essentially identically to Xantphos in Rh-catalyzed hydroformylation of 1-octene, which suggests that the high regioselectivity for linear aldehyde is due to the large bite angle of these ligands and is not influenced by oxygen coordination to the metal. The Pd-catalyzed amidocarbonylation of 4-bromoanisole with dimethylhydroxylamine hydrochloride similarly showed no difference between Xantphos and XL-Xantphos. Computations on Pd(II) phosphine complexes at the DLPNO-CCSD(T) level of theory indicated that these ligands have different preferences for cis and trans coordination modes. The XL-Xantphos ligand has a thermodynamic preference for trans-chelated structures, whereas the cis-[(Xantphos)PdCl2] isomer was calculated to be thermodynamically more stable than its trans isomer. Given the key role of d8 square planar Pd intermediates in many catalytic cycles, the greater preference of Xantphos to form cis chelates may indeed be a factor which has made this ligand particularly effective.
- Whiteker, Gregory T.,Li, Fangzheng,Froese, Robert D. J.,Tulchinsky, Michael L.,Hazari, Amaruka,Klosin, Jerzy
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- Synthesis of two new Mo(II) organometallic catalysts immobilized on POSS for application in olefin oxidation reactions
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The purpose of this work was the preparation and characterization of two new catalysts POSS-ATZAc-[Mo(η3-C3H5)Br(CO)2] (POSS-Mo-I) and POSS-ATZAc-[Mo(CO)3Br2] (POSS-Mo-II). The new heterogeneous catalysts were characterized by several techniques and used as catalysts for the epoxidation of olefins, presenting high catalytic activity. To study and optimize the syntheses of the heterogeneous catalysts, immobilization experiments of the [Mo(η3-C3H5)Br(CO)2(NCMe)2] and [Mo(CO)3Br2(NCMe)2] organometallic complexes on the modified polyhedral oligomeric silsesquioxane were performed. The sorption properties of the modified silsesquioxane showed to be dependent of the contact time, concentration and temperature. Catalysts were tested in the epoxidation of six olefins and compared with homogeneous species [Mo(η3-C3H5)Br(CO)2(ATZAc)] (Mo-I) and [Mo(CO)3Br2(ATZAc)] (Mo-II). To the best of our knowledge, this paper is the first that has reported the preparation and characterization of two new heterogeneous catalysts, as well as the comparison with homogeneous species for catalytic epoxidation of olefins.
- Vieira, Eduardo Guimar?es,Dal-Bó, Alexandre Gon?alves,Frizon, Tiago Elias Allievi,Dias Filho, Newton Luiz
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- POSS-derived mesoporous ionic copolymer-polyoxometalate catalysts with a surfactant function for epoxidation reactions
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A series of novel polyoxometalate (POM)-based stable polymeric hybrids were successfully synthesized using polyhedral oligomeric vinylsilsesquioxanes (POSS) and ionic liquids (IL) bearing hydrophobic alkyl chains as the building blocks, followed by ion exchange with Keggin-type phosphotungstic acid (PW). The obtained hybrids POSS-ILx-PW were demonstrated to be mesostructured and amphiphilic materials with good thermal stability. Catalytic tests for the H2O2-based epoxidation of cyclooctene have shown that these newly designed catalysts exhibit extraordinary catalytic activities, catalytic rates, and quite stable reusability. The unique amphiphilic property and the mesoporous structure are revealed to be responsible for the catalysts' excellent performance in epoxidation reactions with H2O2.
- Zhao, Jiwei,Leng, Yan,Jiang, Pingping,Wang, Jun,Zhang, Chenjun
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- Readily Accessible 12-I-5 Oxidant for the Conversion of Primary and Secondary Alcohols to Aldehydes and Ketones
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Periodinane 2 is a mild, selective reagent for the oxidation of primary and secondary alcohols to aldehydes and ketones.
- Dess, D. B.,Martin, J. C.
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- Trimethylsilylation of ordered and disordered titanosilicates: Improvements in epoxidation with aqueous H2O2 from micro- to meso-pores and beyond
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A novel method for trimethylsylilation of micro- and mesoporous titanosilcates using BSTFA [N,O-bis(trimethylsilyl)trifluoroacetamide] renders Ti-MCM-41 and SiO2/TiO2 aerogels active for olefin epoxidation with aqueous H2O2, and even improves the activity of TS-1.
- D'Amore, Michael B.,Schwarz, Stephan
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- Novel approach to synthesizing polymer-functionalized Fe3O4/SiO2-NH2via an ultrasound-assisted method for catalytic selective oxidation of alcohols to aldehydes and ketones in a DMSO/water mixture
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N-(2-Oxotetrahydrothiophen-3-yl)acrylamide was successfully polymerized on the surface of amine functionalized magnetic silica nanocomposites via an ultrasound-assisted method. Then, MnO2 nanoparticles were formed on the surface of the polymer
- Dehghan, Mahsa,Motaharinejad, Atieh,Saadat, Mostafa,Ahdenov, Reza,Babazadeh, Mirzaagha,Hosseinzadeh-Khanmiri, Rahim
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- Au/TiO2 catalysts promoted with Fe and Mg for n-octanol oxidation under mild conditions
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This work aims to further the understanding of gold-based catalytic oxidation of n-octanol in liquid phase. Modification of catalysts with metal oxides additives (Fe or Mg) was used as a tool for transforming and stabilizing gold species. Structural, electronic and catalytic properties of gold catalysts were systematically investigated by means of DRS, H2, CO FTIR, SBET, EDS and SEM, HRTEM, SR-XRD, XANES, XPS and liquid phase n-octanol oxidation. Addition of modifiers affects Au electronic properties, but not the structural ones. Characterization results allow excluding Au3+ ions as candidates for active sites in n-octanol oxidation. In Au/Mg/TiO2, gold exhibited more reduced states while in Au/Fe/TiO2 gold was more oxidized; Au/TiO2 for intermediate oxidized states was found. The proper balance of oxidation states in the gold surface of Au/Mg/TiO2 can be responsible for its higher activity compared with Au/Fe/TiO2 and Au/TiO2 towards n-octanol oxidation. Finally our approach shed light on the nature of active sites for n-octanol oxidation on gold and furthers the development of green base-free catalytic oxidation of alcohols.
- Kotolevich,Kolobova,Mamontov,Khramov,Cabrera Ortega,Tiznado,Farías,Bogdanchikova,Zubavichus, Ya.,Mota-Morales,Cortés Corberán,Zanella,Pestryakov
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- New approach to rapid generation and screening of diverse catalytic materials on electrode surfaces
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This paper describes a general approach to rapid generation and screening of catalytic materials on electrode surfaces. The properties of the corresponding polymers, including catalytic performance, can be modulated by varying the monomer feed ratios, monomer concentrations, and applied polymerization potential. Thus, the generation of the polymeric TEMPO (2,2,6,6-tetramethylpiperidin-1-yloxy) catalysts was performed by electrochemical copolymerization of 2,2'-bithiophene with the TEMPO catalyst precursors containing pyrrole side chains. A library of catalyst films was obtained over a wide range of bithiophene/pyrrole ratios upon repeated scanning of the applied potential from +0.5 to +1.4 V (vs Ag/AgCl). The resulting catalyst films were utilized in both chemical and electrochemical oxidation of primary alcohols to aldehydes.
- Siu,Yekta,Yudin
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- Room temperature liquid salts of Cr and Mo as self-supported oxidants
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Room temperature liquid salts of Cr and Mo were synthesized and fully characterized including cyclic voltammetry of the neat Mo salt. These liquid salts were used as self-supported reagents for the oxidation of alcohols (under solvent-free and biphasic conditions) and their potential for biphasic self-supported catalytic applications was demonstrated.
- Noguera, Gladys,Mostany, Jorge,Agrifoglio, Giuseppe,Dorta, Romano
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- ACTIVATION AND SYNTHETIC APPLICATIONS OF THIOSTANNANES. CHEMICAL MODIFICATION OF HYDROXY FUNCTION UNDER PROTECTION
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Tetrahydropyranyl ethers are converted in one-pot into benzyl and α-methoxyethoxymethyl ethers, benzoates, tosylates, and aldehydes on treatment with thiostannanes in the presence of BF3*OEt2 followed by exposure of the resulting alkoxystannanes to electrophiles or PCC.
- Sato, Tsuneo,Tada, Tatsushi,Otera, Junzo,Nozaki, Hitosi
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- Nickel(II), copper(II), cobalt(II), and palladium(II) complexes with a Schiff base: Crystal structure, DFT study and copper complex catalyzed aerobic oxidation of alcohol to aldehyde
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Ni(II), Cu(II), Co(II), and Pd(II) complexes were synthesized with a Schiff base containing thioether with ONS donors chelating to the metal center. The ligand and complexes were characterized by elemental analysis, FT-IR, 1H-NMR, UV-visible sp
- Sarma, Kuladip,Devi, Namita,Kalita, Mukul,Sarma, Bipul,Barman, Pranjit
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- The effect of support properties on n-octanol oxidation performed on gold – silver catalysts supported on MgO, ZnO and Nb2O5
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Catalytic behaviour of supported nanometal catalysts for alcohols selective oxidation depends on the nature of the support and its surface. To identify the main feature that could explain these effects, supported mono- (Au) and bimetallic (AuAg) catalysts were prepared by using pure MgO, ZnO and Nb2O5, representative of three different types of oxides (basic, amphoteric and acidic, respectively), to get homogeneous metal-support interaction for each catalyst. The catalysts were characterized by XRD, N2 physisorption, TEM, UV–vis, XPS and 2-propanol decomposition as test reaction. It was found that the catalytic activity is influenced by the electron mobility between the gold nanoparticles and the support, which in turns depends on the intermediate electronegativity of the support. Selectivity in n-octanol oxidation was determined by redox properties of the gold species, the acid-base properties of the supports and the catalyst pretreatment. Silver addition modified the acid-base properties of the catalytic system, thus influencing the selectivity in n-octanol oxidation. Pretreatment of the catalyst (drying in air or thermal treatment in hydrogen flow) had a significant impact on its activity and selectivity.
- Kaskow, Iveta,Sobczak, Izabela,Ziolek, Maria,Corberán, Vicente Cortés
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- Apatitic Tricalcium Phosphate as Novel Smart Solids for Supported Aqueous Phase Catalysis (SAPC)
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Apatitic tricalcium phosphate was used as support for supported aqueous phase catalysis (SAPC) in the hydroformylation reaction of oct-1-ene, at 80°C in toluene using a dinuclear rhodium complex bearing TPPTS as hydrophilic ligands. The reaction yield is
- Dessoudeix,Jauregui-Haza,Heughebaert,Wilhelm,Delmas,Lebugle,Kalck
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- Hydroformylation of 1-hexene over rhodium supported on active carbon catalyst
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Hydroformylation of 1-hexene on rhodium catalyst was studied under mild reaction conditions (P = 3.0 MPa, CO/H2 = 1/1, T = 403 K). Its hydroformylation performances were investigated in a variety of solvent. It was found that the excellent activity for the heterogeneous catalyst was showed in the n-octane solvent, while poor activity in the alcoholic and H2O solvent.
- Li, Baitao,Li, Xiaohong,Asami, Kenji,Fujimoto, Kaoru
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- One alkenylphenol and steroids from the aquatic plant Monochoria vaginalis
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Two new compounds have been isolated from the whole plant of Monochoria vaginalis and characterized as: (10Z)-1-(2,6-dihydroxyphenyl)octadec-10-en-1-one (1) (20R,24R)-campest-5-ene-3β,4β-diol (2) together with nine known ones. The structures of these comp
- Row, Lie-Ching,Chen, Chiu-Ming,Ho, Jiau-Ching
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- Pyridinium chlorochromate: An improved method for its synthesis and use of anhydrous acetic acid as catalyst for oxidation reactions
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An improved procedure for the preparation of Corey's reagent - Pyridinium chlorochromate has been described. The method is less hazardous and gives better yield. Synthetic utility of the reagent has been shown to increase in the presence of anhydrous acetic acid, used for the first time as catalyst, for the oxidation of alcohols.
- Agarwal, Seema,Tiwari,Sharma
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- Syntheses and catalytic activities of new metallodendritic catalysts
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This investigation presents the syntheses of new metallodendritic catalysts from a silsesquioxane core (Silsesq-PrNH3+Cl-) via a new route. For optimization of the syntheses of the catalysts, reaction times, thermodynamic effects, and the amounts of [Mo(η3-C3H5)Br(CO)2(NCCH3)2] (1) and [Mo(CO)3Br2(NCCH3)2] (2) complexes fixed on the second-generation dendrimer (PDG2.0) were studied. After the optimization studies and with the objective of application in catalysis, the catalysts were prepared by reaction of PDG2.0 with the organometallic complexes and characterized by elemental analysis (CNH), FTIR, 13C and 29Si NMR, XRD, TGA, SEM, EDS and BET. The metallodendritic catalysts were tested in the epoxidation of olefins and shown to be a vigorous catalyst with conversion rates between 76 and 97% for PDG2.0-[(Mo(η3-C3H5)(CO)2Br)8] and 30-80% for PDG2.0-[(Mo(CO)3Br2)5], and a high selectivity in the formation of epoxides using tertbutyl hydroperoxide (TBHP) as an oxidant. The catalysts remain highly active after being used for at least 5 cycles. To the best of our knowledge, this study is the first to have reported the preparation of these new dendritic catalysts, as well as the catalytic comparison with their previous generations in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Dal-Bó, Alexandre Gon?alves,Frizon, Tiago Elias Allievi,Filho, Newton Luiz Dias
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- Not as easy as π: An insertional residue does not explain the π-helix gain-of-function in two-component FMN reductases
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The π-helix located at the tetramer interface of two-component FMN-dependent reductases contributes to the structural divergence from canonical FMN-bound reductases within the NADPH:FMN reductase family. The π-helix in the SsuE FMN-dependent reductase of the alkanesulfonate monooxygenase system has been proposed to be generated by the insertion of a Tyr residue in the conserved α4-helix. Variants of Tyr118 were generated, and their X-ray crystal structures determined, to evaluate how these alterations affect the structural integrity of the π-helix. The structure of the Y118A SsuE π-helix was converted to an α-helix, similar to the FMN-bound members of the NADPH:FMN reductase family. Although the π-helix was altered, the FMN binding region remained unchanged. Conversely, deletion of Tyr118 disrupted the secondary structural properties of the π-helix, generating a random coil region in the middle of helix 4. Both the Y118A and Δ118 SsuE SsuE variants crystallize as a dimer. The MsuE FMN reductase involved in the desulfonation of methanesulfonates is structurally similar to SsuE, but the π-helix contains a His insertional residue. Exchanging the π-helix insertional residue of each enzyme did not result in equivalent kinetic properties. Structure-based sequence analysis further demonstrated the presence of a similar Tyr residue in an FMN-bound reductase in the NADPH:FMN reductase family that is not sufficient to generate a π-helix. Results from the structural and functional studies of the FMN-dependent reductases suggest that the insertional residue alone is not solely responsible for generating the π-helix, and additional structural adaptions occur to provide the altered gain of function.
- McFarlane, Jeffrey S.,Hagen, Richard A.,Chilton, Annemarie S.,Forbes, Dianna L.,Lamb, Audrey L.,Ellis, Holly R.
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- Amphiphilic phosphotungstate-paired ionic copolymer as a highly efficient catalyst for triphase epoxidation of alkenes with H2O2
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A novel amphiphilic POM-paired ionic copolymer was prepared by the anion-exchange of a newly task-specific designed functionalized-ionic liquid copolymer with H3PW4O16, and characterized by FT-IR, SEM, TG, 1H NMR, and elemental analysis. This catalyst was not only capable of catalyzing the epoxidation of alkenes in a liquid-liquid-solid triphase reaction system, showing high catalytic conversions and selectivity, but also avoids the use of chlorinated solvents. After reaction, the catalyst can be conveniently recovered and steadily reused without the change of catalyst structure. The unique amphiphilic catalyst structure is revealed to be responsible for the catalyst's excellent performances in the epoxidation of alkenes with H2O2 by accelerating the mass transfer. the Partner Organisations 2014.
- Leng, Yan,Wu, Jianghao,Jiang, Pingping,Wang, Jun
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- Triruthenium dodecacarbonyl/triphenylphosphine catalyzed dehydrogenation of primary and secondary alcohols
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Dehydrogenation of alcohols into aldehydes and ketones by Ru 3(CO)12/PPh3 based homogeneous catalysis has been investigated as an alternative for the classical Oppenauer oxidation. Several catalytic systems have been screened in the Oppenauer-like oxidation of alcohols. A systematic study of various combinations of Ru3(CO) 12, mono- and bidentate ligands and hydride acceptors was performed to enable dehydrogenation of primary alcohols to stop at the aldehyde stage. Among many H-acceptors screened, diphenylacetylene (tolane) proved the most suitable judged from its smooth reduction. Electron rich and deficient analogues of tolane have been synthesized and, based on competition experiments between these H-acceptors, a tentative catalytic cycle for the Ru 3(CO)12/PPh3-catalyzed dehydrogenations has been proposed.
- Meijer,Ligthart,Meuldijk,Vekemans,Hulshof,Mills,Kooijman,Spek
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- Novel allylic oxidation reagents
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Pentafluorobenzeneseleninic acid and 2-(N-oxido)pyridineseleninic anhydride were prepared and used efficiently in the oxidation of alcohols and in the allylic oxidation of alkenes.
- Barton, Derek H. R.,Wang, Tie-Lin
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- Asymmetric synthesis of (-)-acaterin
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The asymmetric synthesis of (-)-acaterin, an inhibitor of acyl-CoA cholesterol acyl transferase has been achieved starting from the commercially available starting materials, octan-1-ol and methyl (R)-lactate. The key steps are a Sharpless asymmetric dihydroxylation and a Wittig olefination.
- Kandula, Subba Rao V.,Kumar, Pradeep
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- Microwave-assisted oxidation of alcohols using Magtrieve
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Primary and secondary alcohols can be selectively oxidized under microwave irradiation into the corresponding aldehydes and ketones within 5-30min using commercially available and magnetically retrievable Magtrieve.
- Bogdal,Lukasiewicz,Pielichowski,Miciak,Bednarz
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- One-Pot Bioelectrocatalytic Conversion of Chemically Inert Hydrocarbons to Imines
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Petroleum hydrocarbons are our major energy source and an important feedstock for the chemical industry. With the exception of combustion, the deep conversion of chemically inert hydrocarbons to more valuable chemicals is of considerable interest. However, two challenges hinder this conversion. One is the regioselective activation of inert carbon-hydrogen (C-H) bonds. The other is designing a pathway to realize this complicated conversion. In response to the two challenges, a multistep bioelectrocatalytic system was developed to realize the one-pot deep conversion from heptane to N-heptylhepan-1-imine under mild conditions. First, in this enzymatic cascade, a bioelectrocatalytic C-H bond oxyfunctionalization step based on alkane hydroxylase (alkB) was applied to regioselectively convert heptane to 1-heptanol. By integrating subsequent alcohol oxidation and bioelectrocatalytic reductive amination steps based on an engineered choline oxidase (AcCO6) and a reductive aminase (NfRedAm), the generated 1-heptanol was successfully converted to N-heptylhepan-1-imine. The electrochemical architecture provided sufficient electrons to drive the bioelectrocatalytic C-H bond oxyfunctionalization and reductive amination steps with neutral red (NR) as electron mediator. The highest concentration of N-heptylhepan-1-imine achieved was 0.67 mM with a Faradaic efficiency of 45% for C-H bond oxyfunctionalization and 70% for reductive amination. Hexane, octane, and ethylbenzene were also successfully converted to the corresponding imines. Via regioselective C-H bond oxyfunctionalization, intermediate oxidation, and reductive amination, the bioelectrocatalytic hydrocarbon deep conversion system successfully realized the challenging conversion from inert hydrocarbons to imines that would have been impossible by using organic synthesis methods and provided a new methodology for the comprehensive conversion and utilization of inert hydrocarbons.
- Chen, Hui,Tang, Tianhua,Malapit, Christian A.,Lee, Yoo Seok,Prater, Matthew B.,Weliwatte, N. Samali,Minteer, Shelley D.
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p. 4047 - 4056
(2022/02/10)
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- Controlled reduction of activated primary and secondary amides into aldehydes with diisobutylaluminum hydride
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A practical method is disclosed for the reduction of activated primary and secondary amides into aldehydes using diisobutylaluminum hydride (DIBAL-H) in toluene. A wide range of aryl and alkyl N-Boc, N,N-diBoc and N-tosyl amides were converted into the corresponding aldehydes in good to excellent yields. Reduction susceptible functional groups such as nitro, cyano, alkene and alkyne groups were found to be stable. Broad substrate scope, functional group compatibility and quick conversions are the salient features of this methodology.
- Azeez, Sadaf,Kandasamy, Jeyakumar,Sabiah, Shahulhameed,Sureshbabu, Popuri
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supporting information
p. 2048 - 2053
(2022/03/31)
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- The effect of the position of cross-linkers on the structure and microenvironment of PPh3moiety in porous organic polymers
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Three trivinyl functionalization triphenylphosphine (3vPPh3)-based porous organic ligands (3vPPh3-POLs) with cross-linkers in different positions were obtained through solvothermal polymerization. By simply changing the position of the cross-linkers (vinyl groups) attached to the PPh3monomer, the resulting porous organic polymer (POP) materials acquired diverse hierarchical porous structures, and the microenvironment of POPs was sequently regulated. Among the three 3vPPh3-POLs, the BET surface areas ranged from 168 to 1583 m2g?1, while the proportion of micropores changed from 0.0% to 52.0%. Benefiting from the unique structure, Rh ions could be coordinated and dispersed as a single site inm-3vPPh3-POL to form HRh(CO)2(PPh3-POL)2species, which endowed the Rh/m-3vPPh3-POL catalyst with an activity similar to that in the homogeneous system, anl/bratio (the ratio of the linear aldehyde to the branched aldehyde) approximately as high as 10, and stability for a duration of more than 500 h in the hydroformylation of 1-octene.
- Ji, Guangjun,Li, Cunyao,Xiao, Dong,Wang, Guoqing,Sun, Zhao,Jiang, Miao,Hou, Guangjin,Yan, Li,Ding, Yunjie
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p. 9165 - 9174
(2021/04/16)
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- Enhancing the activity, selectivity, and recyclability of Rh/PPh3 system-catalyzed hydroformylation reactions through the development of a PPh3-derived quasi-porous organic cage as a ligand
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In contrast to heterogeneous network frameworks (e.g., covalent organic frameworks and metal-organic frameworks) and porous organic polymers, porous organic cages (POCs) are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis. Herein, we report a triphenylphosphine-derived quasi-porous organic cage (denoted as POC-DICP) as an efficient organic molecular cage ligand for Rh/PPh3 system-catalyzed homogeneous hydroformylation reactions. POC-DICP not only displays enhanced hydroformylation selectivity (aldehyde selectivity as high as 97% and a linear-to-branch ratio as high as 1.89) but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems. We speculate that the reason for the high activity and good selectivity is the favorable geometry (cone angle = 123.88°) and electronic effect (P site is relatively electron-deficient) of POC-DICP, which were also demonstrated by density functional theory calculations and X-ray absorption fine-structure characterization.
- Wang, Wenlong,Li, Cunyao,Zhang, Heng,Zhang, Jiangwei,Lu, Lanlu,Jiang, Zheng,Cui, Lifeng,Liu, Hongguang,Yan, Li,Ding, Yunjie
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p. 1216 - 1226
(2021/03/06)
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- A TEMPO-Functionalized Ordered Mesoporous Polymer as a Highly Active and Reusable Organocatalyst
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The properties of high stability, periodic porosity, and tunable nature of ordered mesoporous polymers make these materials ideal catalytic nanoreactors. However, their application in organocatalysis has been rarely explored. We report herein for the first time the incorporation of a versatile organocatalyst, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), into the pores of an FDU-type mesoporous polymer via a pore surface engineering strategy. The resulting FDU-15-TEMPO possesses a highly ordered mesoporous organic framework and enhanced stability, and shows excellent catalytic activity in the selective oxidation of alcohols and aerobic oxidative synthesis of 2-substituted benzoxazoles, benzimidazoles and benzothiazoles. Moreover, the catalyst can be easily recovered and reused for up to 7 consecutive cycles.
- Guo, Ying,Wang, Wei David,Li, Shengyu,Zhu, Yin,Wang, Xiaoyu,Liu, Xiao,Zhang, Yuan
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supporting information
p. 3689 - 3694
(2021/09/29)
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- Visible light-induced photodeoxygenation of polycyclic selenophene Se-oxides
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Photodeoxygenation of dibenzothiophene S-oxide (DBTO) is believed to produce ground-state atomic oxygen [O(3P)] in solution. Compared with other reactive oxygen species (ROS), O(3P) is a unique oxidant as it is potent and selective. Derivatives of DBTO have been used as O(3P)-precursors to oxidize variety of molecules, including plasmid DNA, proteins, lipids, thiols, and other small organic molecules. Unfortunately, the photodeoxygenation of DBTO requires ultraviolet irradiation, which is not an ideal wavelength range for biological systems, and has a low quantum yield of approximately 0.003. In this work, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide, and perylo[1,12-b,c,d]selenophene Se-oxide were synthesized, and their ability to utilize visible light for generating O(3P) was interrogated. Benzo[b]naphtho[1,2-d]selenophene Se-oxide produces O(3P) upon irradiation centered at 420 nm. Additionally, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, and dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide produce O(3P) when irradiated with UVA light and have quantum yields of photodeoxygenation ranging from 0.009 to 0.33. This work increases the utility of photodeoxygenation by extending the range of wavelengths that can be used to generate O(3P) in solution.
- Chintala, Satyanarayana M.,Throgmorton, John C.,Maness, Peter F.,McCulla, Ryan D.
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- Expanding the Biocatalytic Toolbox with a New Type of ene/yne-Reductase from Cyclocybe aegerita
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This study introduces a new type of ene/yne-reductase from Cyclocybe aegerita with a broad substrate scope including aliphatic and aromatic alkenes/alkynes from which aliphatic C8-alkenones, C8-alkenals and aromatic nitroalkenes were the preferred substrates. By comparing alkenes and alkynes, a ～2-fold lower conversion towards alkynes was observed. Furthermore, it could be shown that the alkyne reduction proceeds via a slow reduction of the alkyne to the alkene followed by a rapid reduction to the corresponding alkane. An accumulation of the alkene was not observed. Moreover, a regioselective reduction of the double bond in α,β-position of α,β,γ,δ-unsaturated alkenals took place. This as well as the first biocatalytic reduction of different aliphatic and aromatic alkynes to alkanes underlines the novelty of this biocatalyst. Thus with this study on the new ene-reductase CaeEnR1, a promising substrate scope is disclosed that describes conceivably a broad occurrence of such reactions within the chemical landscape.
- Karrer, Dominik,Gand, Martin,Rühl, Martin
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p. 2191 - 2199
(2021/02/26)
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- Catalytic alcohol oxidation using cationic Schiff base manganeseIII complexes with flexible diamino bridge
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Four Schiff base manganese(III) complexes with derivatives of [(R,R)-N,N’-bis(salicy1idene)-1,2-cyclohexanediaminato)] including substituents on salicylaldehyde such as 3-methoxy, 3,5-di-tert-butyl and 3,5-chloro were synthesized and characterized using a combination of IR, UV–Vis, and HR ESI-MS techniques. The catalytic activity of these complexes was tested in the oxidation of 1-phenylethanol to acetophenone, revealing very good performances for all of the four manganese complexes. The catalytic reactions were carried out in the presence of tert-butyl hydroperoxide (TBHP) as oxidant and imidazole as co-catalyst. Complex Mn-4, bearing electron withdrawing [(R,R)-N,N’-bis(3,5-di-chloro-salicylidene)-1,2-cyclohexanediaminato)] ligand was found to be the most stable of the tested Mn(III) complexes and was selected for the oxidation of several primary and secondary alcohols.
- Kakavand, Meysam,Mastrorilli, Piero,Mesto, Ernesto,Neshat, Abdollah,Osanlou, Farzane,Schingaro, Emanuela,Todisco, Stefano
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- Ruthenium(ii)-supported phosphovanadomolybdates [Ru(dmso)3PMo6V3O32]6-and [Ru(PMo6V3O32)2]14-, and their use as heterogeneous catalysts for oxidation of alcohols
-
Self-assembly of cis-[RuCl2(dmso)4], NaVO3, Na2MoO4 and NaH2PO4 in a molar ratio of 1?:?3?:?6?:?1 in HOAc-NaOAc buffer (pH = 4-5) in the presence of CsCl gave a ruthenium(ii)-supported phosphovanadomolybdate [RuII(dmso)3PMoVI6VV3O32]6- (1). While a similar reaction with the reactants in a molar ratio of 1?:?6?:?12?:?2 afforded a ruthenium substituted "sandwich"type polyoxometalate [RuII(PMoVI6VV3O32)2]14- (2). Clusters 1 and 2 were well characterized by single-crystal X-ray diffraction. Their use as heterogeneous catalysts for oxidation of alcohols in the presence of molecular oxygen was also investigated.
- Shi, Hao-Yu,Zhou, Wen-Yan,Song, Xiao-Ming,Jia, Ai-Quan,Shi, Hua-Tian,Zhang, Qian-Feng
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p. 1551 - 1555
(2021/02/06)
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- Pt-Catalyzed selective oxidation of alcohols to aldehydes with hydrogen peroxide using continuous flow reactors
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The oxidation of alcohols to aldehydes is a powerful reaction pathway for obtaining valuable fine chemicals used in pharmaceuticals and biologically active compounds. Although many oxidants can oxidize alcohols, only a few hydrogen peroxide oxidations can be employed to continuously synthesize aldehydes in high yields using a liquid-liquid two-phase flow reactor, despite the possibility of the application toward a safe and rapid multi-step synthesis. We herein report the continuous flow synthesis of (E)-cinnamaldehyde from (E)-cinnamyl alcohol in 95%-98% yields with 99% selectivity for over 5 days by the selective oxidation of hydrogen peroxide using a catalyst column in which Pt is dispersed in SiO2. The active species for the developed selective oxidation is found to be zero-valent Pt(0) from the X-ray photoelectron spectroscopy measurements of the Pt surface before and after the oxidation. Using Pt black diluted with SiO2as a catalyst to retain the Pt(0) species with the optimal substrate and H2O2introduction rate not only enhances the catalytic activity but also maintains the activity during the flow reaction. Optimizing the contact time of the substrate with Pt and H2O2using a flow reactor is important to proceed with the selective oxidation to prevent the catalytic H2O2decomposition.
- Kon, Yoshihiro,Nakashima, Takuya,Yada, Akira,Fujitani, Tadahiro,Onozawa, Shun-Ya,Kobayashi, Shū,Sato, Kazuhiko
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supporting information
p. 1115 - 1121
(2021/02/16)
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- Low-Temperature Hypergolic Ignition of 1-Octene with Low Ignition Delay Time
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The attainment of the efficient ignition of traditional liquid hydrocarbons of scramjet combustors at low flight Mach numbers is a challenging task. In this study, a novel chemical strategy to improve the reliable ignition and efficient combustion of hydrocarbon fuels was proposed. A directional hydroboration reaction was used to convert hydrocarbon fuel into highly active alkylborane, thereby leading to changes in the combustion reaction pathway of hydrocarbon fuel. A directional reaction to achieve the hypergolic ignition of 1-octene was designed and developed by using Gaussian simulation. Borane dimethyl sulfide (BDMS), a high-energy additive, was allowed to react spontaneously with 1-octene to achieve the hypergolic ignition of liquid hydrocarbon fuel at -15 °C. Compared with the ignition delay time of pure 1-octene (565 °C), the ignition delay time of 1-octene/BDMS (9:1.2) decreased by 3850% at 50 °C. Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry confirmed the directional reaction of the hypergolic ignition reaction pathway of 1-octene and BDMS. Moreover, optical measurements showed the development trend of hydroxyl radicals (OH·) in the lower temperature hypergolic ignition and combustion of 1-octene. Finally, this study indicates that the enhancement of the low-temperature ignition performance of 1-octene by hydroboration in the presence of BDMS is feasible and promising for jet propellant design with tremendous future applications.
- Sheng, Haoqiang,Huang, Xiaobin,Chen, Zhijia,Zhao, Zhengchuang,Liu, Hong
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p. 423 - 434
(2021/02/05)
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- The effects of metals and ligands on the oxidation of n-octane using iridium and rhodium “PNP” aminodiphosphine complexes
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Ir and Rh “PNP” complexes with different ligands are utilized for the oxidation of n-octane. Based on the obtained conversion, selectivity, and the characterized recovered catalysts, it is found that the combination of Ir and the studied ligands does not promote the redox mechanism that is known to result in selective formation of oxo and peroxo compounds [desired species for C(1) activation]. Instead, they support a deeper oxidation mechanism, and thus higher selectivity for ketones and acids is obtained. In contrast, these ligands seem to tune the electron density around the Rh (in the Rh-PNP complexes), and thus result in a higher n-octane conversion and improved selectivity for the C(1) activated products, with minimized deeper oxidation, in comparison to Ir-PNP catalysts.
- Naicker, Dunesha,Alapour, Saba,Friedrich, Holger B
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p. 282 - 289
(2020/12/01)
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- Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol
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The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h?1, and 30 atm H2). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru3Sn7 alloy phase as well as SnOx. Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru3Sn7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnOx and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.
- Hidajat, Marcel Jonathan,Hwang, Dong-Won,Yun, Gwang-Nam
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- Methyl-modified cage-type phosphorus ligand and preparation method thereof Preparation method and application thereof
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The invention discloses a methyl-modified cage-type phosphorus ligand, a preparation method and application thereof, in particular to a synthesis design, wherein methyl is further introduced on a phenyl ring of triphenylphosphine, and a methyl-modified cage-type phosphorus ligand is synthesized, and when a methyl meta-substituted cage-type phosphorus ligand is used as a hydroformylation reaction catalyst the proportion of n-structural aldehyde and isomeric aldehyde is 2.6. TOF-1 The methyl-substituted cage-type phosphorus ligand is excellent in performance, stable in property and recyclable, has excellent substrate applicability in the hydroformylation catalytic reaction, has a good industrial application prospect, and has very important significance in metal organic catalysis.
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Paragraph 0075-0084; 0087-0088
(2021/09/15)
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- Chemo- And regioselective hydroformylation of alkenes with CO2/H2over a bifunctional catalyst
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As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway.
- Hua, Kaimin,Liu, Xiaofang,Wei, Baiyin,Shao, Zilong,Deng, Yuchao,Zhong, Liangshu,Wang, Hui,Sun, Yuhan
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supporting information
p. 8040 - 8046
(2021/11/01)
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- Iron-Catalyzed C-C Single-Bond Cleavage of Alcohols
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An iron-catalyzed deconstruction/hydrogenation reaction of alcohols through C-C bond cleavage is developed through photocatalysis, to produce ketones or aldehydes as the products. Tertiary, secondary, and primary alcohols bearing a wide range of substituents are suitable substrates. Complex natural alcohols can also perform the transformation selectively. A investigation of the mechanism reveals a procedure that involves chlorine radical improved O-H homolysis, with the assistance of 2,4,6-collidine.
- Liu, Wei,Wu, Qiang,Wang, Miao,Huang, Yahao,Hu, Peng
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supporting information
p. 8413 - 8418
(2021/11/01)
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- SBA15-supported nano-ruthenium catalyst for the oxidative cleavage of alkenes to aldehydes under flow conditions
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SBA15-supported ruthenium nanoparticles were prepared and employed as catalytic system for the oxidative cleavage of olefins under flow conditions. Design of experiments was adopted to optimize the reaction parameters and was instrumental to develop a fast and robust method for producing aldehydes from alkenes. Utilizing a simple flow set-up, the process provided high conversions in only few minutes with 0.5% mol of ruthenium under mild reaction conditions and high flow rates.
- Di Michele, Alessandro,Giovagnoli, Stefano,Filipponi, Paolo,Venturoni, Francesco,Gioiello, Antimo
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- METHOD FOR PRODUCING ALIPHATIC LINEAR PRIMARY ALCOHOLS
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Provided are a method of preparing a linear primary alcohol, a catalyst for converting an α-olefin into an alcohol, and a method of converting an α-olefin into a linear primary alcohol, and the method of preparing a linear primary alcohol according to the present invention includes: charging a reactor with a heterogeneous catalyst including a cobalt oxide and a Cn olefin (S1); bringing the heterogeneous catalyst including a cobalt oxide into contact with the Cn olefin (S2); and supplying the reactor with a synthetic gas to obtain a Cn+1 alcohol (S3).
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-
Paragraph 0097-0099; 0104-0106; 0109
(2020/05/06)
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- Palladium/Copper-catalyzed Oxidation of Aliphatic Terminal Alkenes to Aldehydes Assisted by p-Benzoquinone
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The development of an anti-Markovnikov Wacker-type oxidation for simple aliphatic alkenes is a significant challenge. Herein, a variety of aldehydes can be selectively obtained from various unbiased aliphatic terminal alkenes using PdCl2(MeCN)2/CuCl in the presence of p-benzoquinone (BQ) under mild reaction conditions. Isomerization of the terminal alkene to the internal alkene was suppressed via slow addition of the starting material to the reaction mixture. In addition to the Pd catalyst, CuCl and BQ were essential in order to obtain the anti-Markovnikov product with high selectivity. Terminal alkenes bearing a halogen substituent afforded their corresponding aldehydes with high anti-Markovnikov selectivity. The halogen acts as a directing group in the reaction. DFT calculations indicate that a μ-chloro Pd(II)?Cu(I) bimetallic species with BQ coordinated to Cu is the catalytically active species in the case of a terminal alkene without a directing group.
- Komori, Saki,Yamaguchi, Yoshiko,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3946 - 3955
(2020/07/06)
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- Flavin Nitroalkane Oxidase Mimics Compatibility with NOx/TEMPO Catalysis: Aerobic Oxidization of Alcohols, Diols, and Ethers
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Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NOx - providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NOx and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NOx/TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NOx-generating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (-)-ambroxide to (+)-sclareolide.
- Thapa, Pawan,Hazoor, Shan,Chouhan, Bikash,Vuong, Thanh Thuy,Foss, Frank W.
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p. 9096 - 9105
(2020/08/14)
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- Selective TEMPO-Oxidation of Alcohols to Aldehydes in Alternative Organic Solvents
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The TEMPO-catalyzed oxidation of alcohols to aldehydes has emerged to one of the most widely applied methodologies for such transformations. Advantages are the utilization of sodium hypochlorite, a component of household bleach, as an oxidation agent and the use of water as a co-solvent. However, a major drawback of this method is the often occurring strict limitation to use dichloromethane as an organic solvent in a biphasic reaction medium with water. Previous studies show that dichloromethane cannot easily be substituted because a decrease of selectivity or inhibition of the reaction is observed by using alternative organic solvents. Thus, up to now, only a few examples are known in which after a tedious optimization of the reaction dichloromethane could be replaced. In order to overcome the current limitations, we were interested in finding a TEMPO-oxidation method in alternative organic solvents, which is applicable for various alcohol oxidations. As a result, we found a method for N-oxyl radical-catalyzed oxidation using sodium hypochlorite as an oxidation agent in nitriles as an organic solvent component instead of dichloromethane. Besides the oxidation of aromatic primary alcohols also aliphatic primary alcohols, secondary alcohols as well as dialcohols were successfully converted when using this method, showing high selectivity towards the carbonyl compound and low amounts of the acid side-product.
- Hinzmann, Alessa,Stricker, Michael,Busch, Jasmin,Glinski, Sylvia,Oike, Keiko,Gr?ger, Harald
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supporting information
p. 2399 - 2408
(2020/04/29)
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- Tungstate ion (WO42-) confined in hydrophilic/hydrophobic nanomaterials functionalized br?nsted acidic ionic liquid as highly active catalyst in the selective aerobic oxidation of alcohols in water
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A Br?nsted acidic Ionic Liquid containing tungstate anion functionalized polysiloxane network (PMO-IL-WO42-) was synthesized by simple self-condensation of tungstic acid and zwitterionic organosilane precursor possessing both imidazolium and sulfonate groups. Characterization by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), thermal gravimetric analysis TGA, nitrogen porosimetry, solid-state NMR spectroscopy and elemental analysis confirmed that both imidazolium cation and tungstate anion of zwitterion are successfully incorporated inside the organosilica framework. The catalytic activity of resulting hybrid PMO-IL- WO42- material was studied in the selective aerobic oxidation of primary and secondary alcohols using an atmospheric pressure of air in pure water. Due to the ionic liquid-based charged surface containing hydrophilic sulfonic acid and tungstate group, the synergistic hydrophilic/hydrophobic and redox effect of PMO-IL-WO42- as water-friendly catalyst facilitates and enhances the activity and selectivity toward the target oxidative products in water and proved to have a particularly broad substrate scope for reliable aerobic oxidation reaction. Furthermore, the catalyst showed outstanding stability and could be easily separated and reused at least ten reactions run under the same conditions as fresh catalyst without any loss of catalytic activity and product selectivity.
- Luque, Rafael,Nafe, Mostafa,Rajabi, Fatemeh,Rezanejad Bardajee, Ghasem
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- Method for preparing aldehyde by olefin hydroformylation
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The invention relates to a method for preparing aldehyde through olefin hydroformylation. The method comprises the steps: enabling alpha-olefin and synthesis gas to enter a hydroformylation reactor; carrying out a contact reaction on alpha-olefin and synthesis gas with a catalyst to generate an aldehyde-containing product, wherein the catalyst comprises a main catalyst and a co-catalyst, the maincatalyst is a complex catalyst and comprises a rhodium complex and a phosphine ligand, the phosphine ligand is tris[2,4-di-tert-butylphenyl]phosphite, and the co-catalyst is a nickel-palladium bimetallic phosphinate. The method has the advantages of high normal-to-abnormal ratio in the product, good selectivity and yield, mild reaction conditions and the like.
- -
-
Paragraph 0032-0034; 0035-0039
(2020/07/15)
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- VISIBLE LIGHT INDUCED PHOTOGENERATION OF GROUND STATE ATOMIC OXYGEN
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The present invention generally relates to various polycyclic aromatic selenoxide compounds, methods for preparing these compounds, and methods of us these and other compounds to generate ground state atomic oxygen.
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Paragraph 0094; 0110
(2020/12/01)
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- In Vivo Reduction of Medium- to Long-Chain Fatty Acids by Carboxylic Acid Reductase (CAR) Enzymes: Limitations and Solutions
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Fatty aldehyde production by chemical synthesis causes an immense burden to the environment. Within this study, we explored a sustainable, aldehyde-selective and mild alternative approach by utilizing carboxylic acid reductases (CARs). CARs from Neurospora crassa (NcCAR), Thermothelomyces thermophila (TtCAR), Nocardia iowensis (NiCAR), Mycobacterium marinum (MmCAR) and Trametes versicolor (TvCAR) were overexpressed in E. coli K-12 MG1655 RARE (DE3) and screened for medium- to long-chain fatty acid (C6–C18) reduction. MmCAR showed the broadest tolerance towards all carbon-chain lengths and was selected for further investigations of fatty aldehyde synthesis in whole cells. To yield relevant product concentrations, different limitations of CAR whole-cell conversions were elucidated and compensated. We coupled an in vitro cofactor recycling system to a whole-cell biocatalyst to support cofactor supply and achieved 12.36 g L?1 of octanal (STY 0.458 g L?1 h?1) with less than 1.5 % of 1-octanol.
- Horvat, Melissa,Winkler, Margit
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p. 5076 - 5090
(2020/08/19)
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- Selective Oxidation of Alcohols to Carbonyl Compounds over Small Size Colloidal Ru Nanoparticles
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The selective oxidation of alcohols to corresponding aldehydes is one of the most challenging problems in modern chemistry due to over-oxidation of these products further into corresponding acids and esters. Herein, we report an efficient and eco-friendly method for selective oxidation of aliphatic, unsaturated and aromatic alcohols to aldehydes (>90 %) using small size (2 nm) non-supported colloidal Ru nanoparticles. The selectivity rapidly decreases with increase of the size of nanoparticles (from 2 to 10 nm) or after their deposition over support. X-ray photoelectron spectroscopy suggests that this catalytic performance can be attributed to high content Ru?O species on the surface of small size Ru nanoparticles, which undergo reduction with formation of water and aldehyde and easy oxidation cycles during the reaction according to the Mars-van Krevelen mechanism. The presence of surface oxide layer over small size Ru nanoparticles suppresses over-oxidation of aldehydes to acids.
- Zhao, JingPeng,Hernández, Willinton Y.,Zhou, WenJuan,Yang, Yong,Vovk, Evgeny I.,Capron, Mickael,Ordomsky, Vitaly
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p. 238 - 247
(2019/11/14)
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- Nanocell type Ru?quinone core-shell catalyst for selective oxidation of alcohols to carbonyl compounds
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Selective aerobic oxidation of alcohols to corresponding carbonyl compounds is one of the most important challenges in the modern chemical industry. The existing metal based heterogeneous catalysts provide low selectivity due to over-oxidation of aldehydes to acids and esters. We have found that coating of Ru nanoparticles by disodium anthraquinone-2,6-disulfonate (SQ) results in selective oxidation of aliphatic, unsaturated and aromatic alcohols to aldehydes. Analysis of core-shell Ru?SQ catalyst shows strong interaction between Ru and SQ leading to change of their electronic state and structure. In-situ study of alcohol oxidation using FTIR and electrochemistry indicates on hydrogen abstraction by shell quinone species with hydrogen transfer by quinone to Ru core for water generation. Thus, the catalyst behavior mimics nano-electrocell by separation of oxidation reaction over quinone and reduction of oxygen over Ru providing higher selectivity to aldehyde.
- Capron, M.,Hernández, W. Y.,Naghavi, N.,Ordomsky, V.,Vovk, E. I.,Wu, M.,Yang, Y.,Zhao, J. P.,Zhou, W. J.
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- METHOD FOR PRODUCING CARBONYL COMPOUND
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PROBLEM TO BE SOLVED: To allow a method that oxidizes a first or second alcohol compound to obtain a carbonyl compound to be conducted with a higher yield than that of a method that uses sodium hypochlorite as an oxidizer. SOLUTION: A first or second alcohol compound is oxidized, in the presence of tetraalkylammonium hypochlorite and, preferably, in coexistence with a nitroxy radical catalyst and a metal halide cocatalyst, to produce a carbonyl compound composed of an aldehyde compound, a carboxylic acid compound, and a ketone compound. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPO&INPIT
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-
Paragraph 0062; 0065
(2021/02/04)
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- A chemoselective photolabile protecting group for aldehydes
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A new and high-efficiency photolabile protecting group (PLPG) for aldehydes is described. The PLPG was introduced to aldehydes by using a Lewis acid. Results showed that the PLPG can be released rapidly and smoothly under ultraviolet (UV) irradiation with high efficiency and low cost. This PLPG can easily synthesized and also be selectively protect aldehydes in the presence of ketones.
- Peng, Tao,Wang, Gang,Wang, Lin,Wen, Xiaoxue,Xu, Jing,Xu, Kaijun,Yang, Hongpeng,Zhang, Shouguo
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supporting information
(2020/02/29)
-
- Phosphine ligand, preparation method and application thereof
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The invention provides a preparation method of a phosphine ligand and application of the phosphine ligand in catalyzing olefin hydroformylation reaction. A structural formula of the phosphine ligand is shown as the specification, wherein R, R1, R2 and R3 are selected from C1-C40 alkyl, alkenyl, alkynyl, and phenyl, substituted phenyl, naphthyl, anthryl, phenanthryl or other aromatic ring and aromatic heterocyclic substituents with higher carbon number. The preparation method of the phosphine ligand comprises the following step: carrying out one-step reaction on an isochroman salt and trisilylphosphine under the promotion of villiaumite. The phosphine ligand has strong stability and coordination ability, and can be well coordinated with cobalt, rhodium and other metals, the obtained complex can be used for hydroformylation reaction of terminal olefin, internal olefin, trisubstituted olefin and tetrasubstituted olefin, the catalyst dosage is small, the reaction conditions are mild, andthe yield and selectivity of aldehyde products are very high.
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-
Paragraph 0078-0080
(2020/07/13)
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- The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
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In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
- Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
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p. 11584 - 11591
(2020/11/23)
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- A Cp-based Molybdenum Catalyst for the Deoxydehydration of Biomass-derived Diols
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Dioxo-molybdenum complexes have been reported as catalysts for the deoxydehydration (DODH) of diols and polyols. Here, we report on the DODH of diols using [Cp*MoO2]2O as catalyst (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of [Cp*MoO2]2O, 1.1 equiv. of PPh3 as reductant, and anisole as solvent. Aliphatic vicinal diols are converted to the corresponding olefins by [Cp*MoO2]2O in up to 65 % yield (representing over 30 turnovers per catalyst) and 91 % olefin selectivity, which rivals the performance of other Mo-based DODH catalysts. Remarkably, cis-1,2-cyclohexanediol, which is known as quite a challenging substrate for DODH catalysis, is converted to 30 % of 1-cyclohexene under optimized reaction conditions. Overall, the mass balances (up to 79 %) and TONs per Mo achievable with [Cp*MoO2]2O are amongst the highest reported for molecular Mo-based DODH catalysts. A number of experiments aimed at providing insight in the reaction mechanism of [Cp*MoO2]2O have led to the proposal of a catalytic pathway in which the [Cp*MoO2]2O catalyst reacts with the diol substrate to form a putative nonsymmetric dimeric diolate species, which is reduced in the next step at only one of its Mo-centers before extrusion of the olefin product.
- Li, Jing,Lutz, Martin,Klein Gebbink, Robertus J. M.
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p. 6356 - 6365
(2020/11/30)
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- Non oxidative and oxidative dehydrogenation of: N -octane using FePO4: Effect of different FePO4phases on the product selectivity
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The activation of n-octane with O2 has been investigated over different phases of FePO4 which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions. Catalytic reactions were done with the tridymite-like FePO4 catalyst which showed a high selectivity towards cracked products and carbon oxides. Under dehydrogenation conditions, tridymite phase FePO4 is transformed into the iron pyrophosphate phase (Fe2P2O7). Octenes, aromatics, C8 oxygenates, carbon oxides (COx) and cracked products were present in the product stream. The iron pyrophosphate phase, under oxidative dehydrogenation conditions, showed high selectivity towards cracked products and on regeneration (restoring of the catalytic activity) with molecular oxygen it transformed into the α-phase and quartz type phase. The regenerated catalyst (α-phase and quartz type phase) exhibited a higher selectivity to ODH products when compared to the fresh and deactivated (Fe2P2O7) catalysts. The transformation of both fresh and deactivated catalysts was evident at a temperature of 450 °C. Since the α-phase is the active phase under ODH conditions and transformations between the reduced and α-phase take place reversibly, this could explain the highest selectivity towards octenes within this temperature range. Fresh and regenerated catalysts showed steady state conversions with time under constant conditions, showing that phase transformations were mainly due to varying temperature and oxidative environment. Characterization results show that FePO4 contains fivefold coordinate Fe3+ in the regenerated and fresh catalysts, and this species is believed to be responsible for selective n-octane activation. The surface area, acidity and metal dispersion of the deactivated and regenerated catalyst showed lower values when compared to the fresh catalysts. The results obtained from M?ssbauer spectroscopy showed direct correlation with the XRD data as well as the TPR-TPO results in terms of the phase changes and oxidation state of the calcined, uncalcined, reduced and reoxidised catalyst. This journal is
- Bharuth-Ram, K.,Dasireddy, Venkata D. B. C.,Friedrich, Holger B.,Khan, Faiza B.,Singh, Sooboo
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p. 7591 - 7600
(2020/12/01)
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- Highly efficient and practical aerobic oxidation of alcohols by inorganic-ligand supported copper catalysis
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The oxidation of alcohols to aldehydes or ketones is a highly relevant conversion for the pharmaceutical and fine-chemical industries, and for biomass conversion, and is commonly performed using stoichiometric amounts of highly hazardous oxidants. The aerobic oxidation of alcohols with transition metal complex catalysts previously required complicated organic ligands and/or nitroxyl radicals as co-catalysts. Herein, we report an efficient and eco-friendly method to promote the aerobic oxidation of alcohols using an inorganic-ligand supported copper catalyst 1, (NH4)4[CuMo6O18(OH)6], with O2 (1 atm) as the sole oxidant. Catalyst 1 is synthesized directly from cheap and commonly available (NH4)6Mo7O24·4H2O and CuSO4, which consists of a pure inorganic framework built from a central CuII core supported by six MoVIO6 inorganic scaffolds. The copper catalyst 1 exhibits excellent selectivity and activity towards a wide range of substrates in the catalytic oxidation of alcohols, and can avoid the use of toxic oxidants, nitroxyl radicals, and potentially air/moisture sensitive and complicated organic ligands that are not commercially available. Owing to its robust inorganic framework, catalyst 1 shows good stability and reusability, and the catalytic oxidation of alcohols with catalyst 1 could be readily scaled up to gram scale with little loss of catalytic activity, demonstrating great potential of the inorganic-ligand supported Cu catalysts in catalytic chemical transformations.
- Wei, Zheyu,Ru, Shi,Zhao, Qixin,Yu, Han,Zhang, Gang,Wei, Yongge
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supporting information
p. 4069 - 4075
(2019/08/07)
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- Efficient selective oxidation of alcohols to aldehydes catalyzed by a morpholinone nitroxide
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Efficient chemoselective oxidation of primary alcohols to the corresponding aldehydes is described. The transformation is promoted by a catalytic morpholinone nitroxide radical catalyst which can be easily synthesized. A broad range of substrates includin
- Dong, Zhenhua,Gao, Pengwei,Xiao, Yongmei
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p. 3380 - 3388
(2019/11/05)
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- Catalytic Oxidation of Alcohols Using a 2,2,6,6-Tetramethylpiperidine-N-hydroxyammonium Cation
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The oxidation of alcohols to aldehydes, ketones, and carboxylic acids is reported using 2,2,6,6-tetramethylpiperidine-4-acetamido-hydroxyammonium tetrafluoroborate as a catalyst in conjunction with sodium hypochlorite pentahydrate as a terminal oxidant. The reaction is generally complete within 30–120 min using an acetonitrile/water mix as the solvent, and no additives are required. Product yields are good to excellent and of particular note is that the methodology can be used to access aryl α-trifluoromethyl ketones.
- Miller, Shelli A.,Bisset, Kathryn A.,Leadbeater, Nicholas E.,Eddy, Nicholas A.
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supporting information
p. 1413 - 1417
(2019/01/04)
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- Encapsulated liquid nano-droplets for efficient and selective biphasic hydroformylation of long-chain alkenes
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Aqueous nano-droplets of homogeneous Rh-TPPTS catalyst encapsulated within the cavity of hollow silica nanospheres were fabricated for biphasic hydroformylation of long-chain alkenes, which showed significant reaction rate enhancement effects and improved aldehyde selectivity.
- Zhang, Xiaoli,Wei, Juan,Zhang, Xiaoming
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supporting information
p. 14134 - 14138
(2019/09/18)
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- Photodeoxygenation of phenanthro[4,5-bcd]thiophene S-oxide, triphenyleno[1,12-bcd]thiophene S-oxide and perylo[1,12-bcd]thiophene S-oxide
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Sulfoxides, upon irradiation with ultraviolet (UV) light undergo α-cleavage, hydrogen abstraction, photodeoxygenation, bimolecular photoreduction, and stereo-mutation. The UV irradiation of dibenzothiophene S-oxide (DBTO) yields dibenzothiophene (DBT) as a major product along with ground-state atomic oxygen [O(3P)]. This is a common method for generating O(3P) in solution. The low quantum yield of photodeoxygenation and the requirement of UVA light are drawbacks of using this method. The sulfoxides benzo[b]naphtho-[1,2,d]thiophene S-oxide, benzo[b]naphtho [2,1,d]thiophene S-oxide, benzo[b] phenanthro[9,10-d]thiophene S-oxide, dinaphtho- [2,1-b:1’,2’-d]thiophene S-oxide, and dinaphtho[1,2-b:2’,1’-d]thiophene S-oxide have shown to deoxygenate up to three times faster than DBTO upon UVA irradiation; however, the photodeoxygenation of these sulfoxides does not appear to be limited to the production of O(3P). In this work, phenanthro[4,5-bcd]thiophene S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide were synthesized and their photodeoxygenation was studied. Phenanthro[4,5-bcd]thiophene-S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide deoxygenated upon UVA irradiation. However, the common intermediate experiments did not conclusively identify the photodeoxygenation mechanism of these sulfoxides.
- Chintala, Satyanarayana M.,Petroff II, John T.,Barnes, Andrew,McCulla, Ryan D.
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p. 503 - 515
(2019/05/29)
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- Random Mutagenesis-Driven Improvement of Carboxylate Reductase Activity using an Amino Benzamidoxime-Mediated High-Throughput Assay
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Carboxylic acid reductases (CARs) catalyze the direct adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH) dependent reduction of carboxylic acids to their corresponding aldehydes. The identification and improvement of CARs by protein engineering is, however, severely limited by the lack of fast and generic methods to quantify aldehydes. Within this study, we applied a convenient high-throughput assay (HTA) based on amino benzamidoxime (ABAO) that allows the substrate-independent and chemoselective quantification of aldehydes. Random mutagenesis of the well-known CAR from Nocardia iowensis (CARNi) to improve its activity for sterically demanding 2-substituted benzoic acid derivatives was conducted in a KM-dependent fashion, and the HTA applied in the presence of microbial cells. The study identified a hot spot in the active site of CARNi that increased the affinity to 2-methoxybenzoic acid 9-fold upon mutation from glutamine to proline (Q283P). The catalytic performance of CARNiQ283P appeared to be significantly improved also for other substrates such as 2-substituted (2-Cl, 2-Br) as well as 3- and 4-substituted benzoic acids (3-OMe, 4-OMe), and even aliphatic octanoic acid. (Figure presented.).
- Schwendenwein, Daniel,Ressmann, Anna K.,Doerr, Mark,H?hne, Matthias,Bornscheuer, Uwe T.,Mihovilovic, Marko D.,Rudroff, Florian,Winkler, Margit
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supporting information
p. 2544 - 2549
(2019/04/26)
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- Carbene-Catalyzed α-Carbon Amination of Chloroaldehydes for Enantioselective Access to Dihydroquinoxaline Derivatives
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An NHC-catalyzed α-carbon amination of chloroaldehydes was developed. Cyclohexadiene-1,2-diimines are used as amination reagents and four-atom synthons. Our reaction affords optically enriched dihydroquinoxalines that are core structures in natural products and synthetic bioactive molecules.
- Huang, Ruoyan,Chen, Xingkuan,Mou, Chengli,Luo, Guoyong,Li, Yongjia,Li, Xiangyang,Xue, Wei,Jin, Zhichao,Chi, Yonggui Robin
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p. 4340 - 4344
(2019/06/14)
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- Efficient Oxidation of Benzylic and Aliphatic Alcohols Using a Bioinspired Cross-Bridged Cyclam Manganese Complex with H2O2
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The cross-bridged cyclam manganese complex Mn(Me2EBC)Cl2 efficiently catalyzes the oxidation of benzylic and aliphatic alcohols at pH 3 in a mixture of acetonitrile and water at room temperature. The environmentally benign and high oxygen content oxidant H2O2 was adopted. Conversions of the alcohols to the corresponding carbonyl compounds reached 98 % with good to excellent selectivity. In addition, several lignin model compounds were also catalytically oxidized under these conditions, with excellent conversion (up to 96 %) and selectivity (up to 99 %).
- Zhang, Zhan,Khrouz, Lhoussain,Yin, Guochuan,Andrioletti, Bruno
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supporting information
p. 323 - 327
(2018/11/27)
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- Chemoselective Hydrogenation of α,β-Unsaturated Carbonyls Catalyzed by Biomass-Derived Cobalt Nanoparticles in Water
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Herein, we report highly chemoselective hydrogenation of α,β-unsaturated carbonyls to saturated carbonyls catalyzed by cobalt nanoparticles supported on the biomass-derived carbon from bamboo shoots with molecular hydrogen in water, which is the first prototype using a heterogeneous non-noble metal catalyst for such organic transformation as far as we know. The optimal cobalt nanocatalyst, CoOx@NC-800, manifested remarkable activity and selectivity for hydrogenation of C=C in α,β-unsaturated carbonyls under mild conditions. A broad set of α,β-aromatic and aliphatic unsaturated carbonyls were selectively reduced to their corresponding saturated carbonyls in up to 99 % yields with good tolerance of various functional groups. Meanwhile, a new straightforward one-pot cascade synthesis of saturated carbonyls was realized with high activity and selectivity via the cross-aldol condensation of ketones with aldehydes followed by selective hydrogenation. More importantly, this one-pot strategy is applicable for the expedient synthesis of Loureirin A, a versatile bioactive and medicinal molecule, from readily available starting materials, further highlighting the practical utility of the catalyst. In addition, the catalyst can be easily separated for successive reuses without significant loss in both activity and selectivity.
- Song, Tao,Ma, Zhiming,Yang, Yong
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p. 1313 - 1319
(2019/01/25)
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- Enzymatic One-Step Reduction of Carboxylates to Aldehydes with Cell-Free Regeneration of ATP and NADPH
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The direct generation of aldehydes from carboxylic acids is often a challenging synthetic task but undoubtedly attractive in view of abundant supply of such feedstocks from nature. Though long known, biocatalytic carboxylate reductions are at an early stage of development, presumably because of their co-factor requirement. To establish an alternative to whole-cell-based carboxylate reductions which are limited by side reactions, we developed an in vitro multi-enzyme system that allows for quantitative reductions of various carboxylic acids with full recycling of all cofactors and prevention of undesired over-reductions. Regeneration of adenosine 5′-triphosphate is achieved through the simultaneous action of polyphosphate kinases from Meiothermus ruber and Sinorhizobium meliloti and β-nicotinamide adenine dinucleotide 2′-phosphate is reduced by a glucose dehydrogenase. Under these conditions and in the presence of the carboxylate reductases from Neurospora crassa or Nocardia iowensis, various aromatic, heterocyclic and aliphatic carboxylic acids were quantitatively reduced to the respective aldehydes.
- Strohmeier, Gernot A.,Eitelj?rg, Inge C.,Schwarz, Anna,Winkler, Margit
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p. 6119 - 6123
(2019/04/13)
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- Characterization of Type IV Carboxylate Reductases (CARs) for Whole Cell-Mediated Preparation of 3-Hydroxytyrosol
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Fragrance and flavor industries could not imagine business without aldehydes. Processes for their commercial production raise environmental and ecological concerns. The chemical reduction of organic acids to aldehydes is challenging. To fulfill the demand of a mild and selective reduction of carboxylic acids to aldehydes, carboxylic acid reductases (CARs) are gaining importance. We identified two new subtype IV fungal CARs from Dichomitus squalens CAR (DsCAR) and Trametes versicolor CAR (Tv2CAR) in addition to literature known Trametes versicolor CAR (TvCAR). Expression levels were improved by the co-expression of GroEL-GroES with either the trigger factor or the DnaJ-DnaK-GrpE system. Investigation of the substrate scope of the three enzymes revealed overlapping substrate-specificities. Tv2CAR and DsCAR showed a preferred pH range of 7.0 to 8.0 in bicine buffer. TvCAR showed highest activity at pH 6.5 to 7.5 in MES buffer and slightly reduced activity at pH 6.0 or 8.0. TvCAR appeared to tolerate a wider pH range without significant loss of activity. Type IV fungal CARs optimal temperature was in the range of 25–35 °C. TvCAR showed a melting temperature (Tm) of 55 °C indicating higher stability compared to type III and the other type IV fungal CARs (Tm 51–52 °C). Finally, TvCAR was used as the key enzyme for the bioreduction of 3,4-dihydroxyphenylacetic acid to the antioxidant 3-hydroxytyrosol (3-HT) and gave 58 mM of 3-HT after 24 h, which correlates to a productivity of 0.37 g L?1 h?1.
- Horvat, Melissa,Fritsche, Susanne,Kourist, Robert,Winkler, Margit
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p. 4171 - 4181
(2019/04/14)
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- A Redox Strategy for Light-Driven, Out-of-Equilibrium Isomerizations and Application to Catalytic C-C Bond Cleavage Reactions
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We report a general protocol for the light-driven isomerization of cyclic aliphatic alcohols to linear carbonyl compounds. These reactions proceed via proton-coupled electron-transfer activation of alcohol O-H bonds followed by subsequent C-C β-scission of the resulting alkoxy radical intermediates. In many cases, these redox-neutral isomerizations proceed in opposition to a significant energetic gradient, yielding products that are less thermodynamically stable than the starting materials. A mechanism is presented to rationalize this out-of-equilibrium behavior that may serve as a model for the design of other contrathermodynamic transformations driven by excited-state redox events.
- Ota, Eisuke,Wang, Huaiju,Frye, Nils Lennart,Knowles, Robert R.
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supporting information
p. 1457 - 1462
(2019/01/25)
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- Length-Selective Synthesis of Acylglycerol-Phosphates through Energy-Dissipative Cycling
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The main aim of origins of life research is to find a plausible sequence of transitions from prebiotic chemistry to nascent biology. In this context, understanding how and when phospholipid membranes appeared on early Earth is critical to elucidating the prebiotic pathways that led to the emergence of primitive cells. Here we show that exposing glycerol-2-phosphate to acylating agents leads to the formation of a library of acylglycerol-phosphates. Medium-chain acylglycerol-phosphates were found to self-assemble into vesicles stable across a wide range of conditions and capable of retaining mono- and oligonucleotides. Starting with a mixture of activated carboxylic acids of different lengths, iterative cycling of acylation and hydrolysis steps allowed for the selection of longer-chain acylglycerol-phosphates. Our results suggest that a selection pathway based on energy-dissipative cycling could have driven the selective synthesis of phospholipids on early Earth.
- Bonfio, Claudia,Caumes, Cécile,Duffy, Colm D.,Patel, Bhavesh H.,Percivalle, Claudia,Tsanakopoulou, Maria,Sutherland, John D.
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p. 3934 - 3939
(2019/03/08)
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