123-86-4Relevant articles and documents
Characterization of HNbMoO6, HNbWO6 and HTiNbO 5 as solid acids and their catalytic properties for esterification reaction
He,Li,Tang,Yang,Li,Li,Li
, p. 145 - 152 (2012)
HTiNbO5, HNbMoO6·H2O and HNbWO 6·1.5H2O were prepared by proton-exchange of the precursors KTiNbO5, LiNbMoO6 and LiNbWO6, respectively, which were synthesized by a solid-state reaction method. The morphology and the micro-structure were characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). NH 3 temperature-programmed desorption (NH3-TPD) was used to measure the acidic properties of the samples. The Sanderson electronegativity and Kataoka′s bond strength theory were also applied to investigate the acid properties of the as-prepared samples. Finally, their catalytic activities were evaluated through catalyzing the liquid-phase esterification reaction of acetic acid and n-butanol to form n-butyl acetate. It has been revealed that H+ ions existed in different forms and interaction modes with MO bond in the solid acids. The acid strength for these as-prepared samples follows the order HNbMoO6·H2O > HNbWO6·1. 5H2O > HTiNbO5. In this work, HNbMoO 6·H2O presents an excellent catalytic activity for the esterification reaction, while HNbWO6·1.5H2O and HTiNbO5 have little catalytic activity. The result suggested that the catalytic activity of the layered solid acid for the esterification reaction was mainly controlled by gallery height.
PHASE TRANSFER CATALYSTS POLYETHYLENE GLYCOLS IMMOBILIZED ONTO METAL OXIDE SURFACES
Sawicki, Robert A.
, p. 2249 - 2252 (1982)
Catalysts prepared by reacting polyethylene glycol and polyethylene glycol monomethyl ether with both alumina and silica gel were found to be effective phase transfer agents in displacement and oxidation reactions.
Modulation of starch nanoparticle surface characteristics for the facile construction of recyclable Pickering interfacial enzymatic catalysis
Qi, Liang,Luo, Zhigang,Lu, Xuanxuan
, p. 2412 - 2427 (2019)
In this work, maize starch (MS) was successively modified via an esterification reaction with acetic anhydride (AA) and phthalic anhydride (PTA). Combined with the gelatinization-precipitation process, the formed starch nanoparticles at an AA/PTA ratio of 2 (MS-AP (2)) and 3 (MS-AP (3)) had similar regular spheres but distinct surface characteristics. In order to enhance the activity of lipase B from Candida antarctica (CALB) in an organic solvent, we designed an oil-in-water (o/w) and a water-in-oil (w/o) Pickering interfacial catalytic system simultaneously by utilizing MS-AP (2) and MS-AP (3) as robust Pickering emulsion stabilizers. Impressively, during the esterification of 1-butanol and vinyl acetate, the specific activity of CALB in the o/w (0.0843 U μL-1) or w/o (0.0724 U μL-1) Pickering interfacial catalytic system was much higher than that of free enzymes in the monophasic (0.0198 U μL-1) and biphasic (0.0282 U μL-1) system. Moreover, after preliminarily elaborating mass transfer discrepancies between the o/w and w/o Pickering interfacial catalytic systems and calculating their mass transfer resistance, we clarified the effects of the location of these two phases on the catalytic capacity of the Pickering emulsion. Impressively, both Pickering interfacial catalytic systems exhibited high effectiveness in product separation. It was found that the w/o Pickering emulsion enabled the organic product to be facilely isolated through a simple decantation, while the o/w Pickering emulsion achieved similar results after adjusting the system temperature. The bio-based nanomaterials and simple protocol, in conjunction with the stability to simultaneously achieve high catalysis efficiency and excellent recyclability, makes us believe that this starch nanoparticle-based Pickering interfacial catalytic system is a promising system for meeting the requirements of green and sustainable chemistry.
Polymers as reagents and catalysts. Part 28. The effect of polymer catalyst structure on the esterification of acids
Zupan,Segatin
, p. 597 - 609 (1991)
Crosslinked sulphonated polystyrene (Dowex 20 M) and various salts of crosslinked co-poly[styrene-4-vinylpyridine] with hydrogen halides were used as solid catalysts in investigations of the conversion of acids to esters. The role of the structure of the acid (acetic acid, benzoic acid), solvent (n-octane, toluene, n-butanol) and reaction temperature in the presence of polymer supported catalyst was tested in the reaction with n-butanol. Sulphonated crosslinked polystyrene (3a) was the most active catalys, similar activity was found with crosslinked co-poly[styrene-4-vinyl(pyridinium chloride)], while catalysts bearing a fluoride (3b) and iodide (3e) function were almost unreactive. The important role of co-solvents was also established.
Barry et al.
, p. 223 (1976)
A Convenient Synthesis of Isotopically Labelled Anthraquinones, Chrysophanol, Islandicin, and Emodin. Incorporation of Chrysophanol into Tajixanthone in Aspergillus variecolor
Ahmed, Salman A.,Bardshiri, Esfandiar,Simpson, Thomas J.
, p. 883 - 884 (1987)
Cycloaddition reactions of labelled 6-methoxy-3-methyl-2-pyrone (1) with naphthoquinones provide the common fungal anthraquinones, chrysophanol (2), islandicin (3), and emodin (4) suitably labelled for biosynthetic studies, as demonstrated by synthesis and incorporation of chrysophanol into the xanthone metabolite, tajixanthone (17) in Aspergillus variecolor.
Magnetic MOF microreactors for recyclable size-selective biocatalysis
Huo, Jia,Aguilera-Sigalat, Jordi,El-Hankari, Samir,Bradshaw, Darren
, p. 1938 - 1943 (2015)
In this contribution we report a synthetic strategy for the encapsulation of functional biomolecules within MOF-based microcapsules. We employ an agarose hydrogel droplet Pickering-stabilised by UiO-66 and magnetite nanoparticles as a template around which to deposit a hierarchically structured ZIF-8 shell. The resulting microcapsules are robust, highly microporous and readily attracted to a magnet, where the hydrogel core provides a facile means to encapsulate enzymes for recyclable size-selective biocatalysis.
Zr-La doped sulfated titania with a by far better catalytic activity and stability than pure sulfated titania in the esterification of acetic acid and n-butanol
Shi, Wenping
, p. 732 - 738 (2013)
A novel solid superacid catalyst TiO2-Zr-La/SO4 2- was prepared by doping Zr and La to the bulk of TiO2. The modified TiO2-Zr-La/SO4 2- and the unmodified TiO2/SO4 2- were used to catalyze the esterification of acetic acid and n-butanol, in which these two catalysts were systematically compared in a lost of aspects such as catalytic activity and stability and so on. When a small amount of Zr and La were co-doped into the bulk of TiO2, the modified catalyst obtained a by far better catalytic activity and stability than the unmodified, showing that the modified is more resistive to deactivation than the unmodified. Under the set reaction conditions, the average conversion (of acetic acid) and the 20th-cycle conversion (of acetic acid) are 88.83 and 77.35 % for the modified, 80.83 and 46.15 % for the unmodified, respectively. The two catalysts were characterized by means of FTIR, XRD, BET, SEM, TG, and NH3-TPD methods to find the possible reasons for the superiority of the modified catalyst to the unmodified one. The characteristic results indicated that the incorporation of a small amount of Zr and La into the catalyst was beneficial to the modified catalyst: (1) improving its water-tolerance; (2) increasing its surface sulfate group content; (3) decreasing its crystallinity after calcination by retarding its crystallization from amorphous TiO2 to anatase TiO2; (4) increasing its specific surface area; (5) increasing its acidity including the concentration and acid strength of the surface acidic sites of it. All the above advantageous effects arisen from the two-element-doping are to be responsible for the substantially-improved catalytic performances of the modified catalyst.
Production of aroma esters by immobilized Candida rugosa and porcine pancreatic lipase into calcium alginate gel
Ozyilmaz, Gul,Gezer, Esra
, p. 140 - 145 (2010)
Candida rugosa lipase (CRL) and porcine pancreatic lipase (PPL) were immobilized into calcium alginate (Ca-Alg) gel beads by means of entrapment and were used to produce three industrially important flavour esters, namely isoamyl acetate (banana flavour), ethyl valerate (green apple flavour) and butyl acetate (pineapple flavour). Immobilization conditions were optimized in terms of sodium alginate (Na-Alg) and CaCl2 concentrations by determination of the entrapped enzyme amount as well as by esterification of 4-nitrophenol and acetic acid. The best results were obtained at 2.5% Na-Alg and 2.5 M CaCl2 for CRL while at 2.5% Na-Alg and 2.0 M CaCl2 for PPL. On carrying out flavour syntheses in solvent-free medium and also in hexane medium, higher ester yields were obtained in hexane medium for all esters and both types of lipases. Ester esterification efficiency increased in parallel with both enzyme concentrations at immobilization medium and the immobilized lipase amount in esterification medium. Maximum ester production was observed between 40 and 50 °C for CRL and PPL. Besides, the effect of substrate concentrations on ester conversion was remarkable. The best ester yield was obtained for isoamyl acetate when immobilized PPL was used.
Cholinium-based deep eutectic solvents and ionic liquids for lipase-catalyzed synthesis of butyl acetate
Cvjetko Bubalo, Marina,Jurinjak Tu?ek, Ana,Vinkovi?, Marijana,Rado?evi?, Kristina,Gaurina Sr?ek, Vi?nja,Radoj?i? Redovnikovi?, Ivana
, p. 188 - 198 (2015)
The aim of this study was to analyze the advantages and limitations of cholinium-based ionic liquids (ILs) and deep eutectic solvents (DESs) used as green solvents for immobilized Candida antarctica lipase B-catalyzed synthesis. The reaction of acetic anhydride with 1-butanol to give short chain ester butyl acetate was chosen as a model reaction. Results showed that selected ILs (choline glycinate, choline alaninate, choline asparaginate, choline malate) and DESs (choline chloride mixtures with glycerol Gly, ethylene glycol EG, and urea U as hydrogen bond donors in molar ratio 1:2) are poor media for tested reaction if applied as pure solvents (yield 50 >5 mM) for both cell lines. Obtained results suggest that DESs are promising candidates for green biocatalysis.
Molybdena-vanadia supported on alumina: Effective catalysts for the esterification reaction of acetic acid with n-butanol
Mitran, Gheorghita,Pavel, Octavian-Dumitru,Marcu, Ioan-Cezar
, p. 104 - 110 (2013)
The paper describes the preparation of alumina-supported molybdena-vanadia catalysts, their structural and textural characterization using XRD, N 2 adsorption, UV-vis and NH3-TPD techniques as well as their catalytic properties in the esterification reaction of acetic acid with n-butanol. The effects of esterification conditions including reaction time, catalyst loading and acid-to-alcohol mole ratio and of reactant pre-adsorption on the conversion were investigated. The catalytic activity correlated well with the number of strong acid sites which increased by increasing the vanadia content. In optimized conditions, conversions higher than 85% with 100% selectivity for n-butyl acetate can be obtained. Reactant pre-adsorption experiments suggested that the reaction follows the Langmuir-Hinshelwood mechanism. A good reusability of the catalysts after three reaction cycles was observed. A local interaction between molybdenum and vanadium on the catalyst surface has been evidenced.
Hydrogenation of ethyl acetate to ethanol over Ni-based catalysts obtained from Ni/Al hydrotalcite-like compounds
Zhang, Beixiao,Lin, Lu,Zhuang, Junping,Liu, Ying,Peng, Lincai,Jiang, Longfei
, p. 5139 - 5152 (2010)
A series of Ni-based catalysts were prepared using hydrogen reduction of Ni/Al hydrotalcite-like compounds (Ni/Al HTlcs) synthesized by coprecipitation. The physicochemical properties of Ni/Al hydrotalcite-like compounds and the corresponding Ni-based catalysts were characterized using inductively coupled plasma (ICP), BET surface areas, Xray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The results indicated that Ni/Al HTlcs with layered structures could be successfully prepared by the coprecipitation method, and the characteristic HTlcs reflections were also observed in the XRD analysis. The NiO and Ni 0 phases were identified in all Ni-based catalysts, which displayed randomly interconnected pores and no layer structures. In addition, the studies also found the Ni/Al HTlcs and Nibased catalysts had high specific surface areas, low pore volumes and low pore diameters. The catalytic hydrogenation of ethyl acetate to ethanol with Ni-based catalysts was also investigated. Among the studied catalysts, RE1NASH-110-3 showed the highest selectivity and yield of ethyl acetate to ethanol, which were 68.2% and 61.7%, respectively. At thesame time, a major by-product, butyl acetate, was formed due to an ester-exchange reaction. A proposed hydrogenation pathway for ethyl acetate over Ni-based catalysts was suggested.
Kinetic study of transesterification of methyl acetate with n-butanol catalyzed by NKC-9
Baoyun, Xu,Weijiang, Zhang,Xuemei, Zhang,Cuifang, Zhou
, p. 101 - 106 (2009)
The transesterification of methyl, acetate and n-butanol catalyzed by cation-exchange resin, NKC-9, was studied in this work to obtain the reaction kinetics. The experiments were carried out in a stirred batch reactor at different temperatures (328.15, 33
Surface, textural and catalytic properties of pyridinium hydrogen sulfate ionic liquid heterogenized on activated carbon carrier
Avdeev, Georgi,Kolev, Hristo,Tankov, Ivaylo
, (2021)
Pyridinium hydrogen sulfate ionic liquid (PHS) heterogenized on activated carbon (AC) is investigated for the first time in the current paper. For that purpose, the xPHS/AC (x = 8, 17, 33 and 66 wt%) samples are analyzed by a number of physicochemical methods such as N2 adsorption–desorption measurements, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Catalytic activity and reusability of xPHS/AC are evaluated in the reaction of butyl acetate synthesis. Effect of the reaction temperature and catalyst loading on the butyl acetate yield are examined in this work as well. Important thermodynamic parameters such as equilibrium constant, activation energy, Gibbs free energy and activation energy barrier for the reaction of butyl acetate synthesis in the presence of xPHS/AC are determined. Textural characterization revealed the that xPHS/AC are mixed micro-mesoporous materials. The PHS heterogenization on AC affects both ionic liquid and support phases due to a surface PHS–AC interaction. FT-IR and XPS showed that this interaction is: (i) manly expressed as a close contact between the pyridinium cation and the functional groups on the AC surface and (ii) electrostatic in nature. The existence of a PHS–AC interaction is found to be responsible for the formation of surface PHS particles of various size. However, the catalytic activity of xPHS/AC is established to be affected by the surface active phase amount, but not the PHS particle size.
Zinc oxide as a solid acid catalyst for esterification reaction
Nagvenkar, Anjani,Naik, Sajo,Fernandes, Julio
, p. 20 - 23 (2015)
Zinc oxide and its composites with Hβ zeolite were produced under different synthesis conditions. The synthesized catalysts were evaluated for performance in esterification of n-butanol with acetic acid. BET surface area, XRD, and acidity (using NH3 and pyridine as probe molecules) were measured to correlate the activity with the structural features of the catalysts.
High-temperature synthesis of magnetically active and SO 3H-functionalized ordered mesoporous carbon with good catalytic performance
Liu, Fujian,Sun, Jing,Sun, Qi,Zhu, Longfeng,Wang, Liang,Meng, Xiangju,Qi, Chenze,Xiao, Feng-Shou
, p. 115 - 120 (2012)
Magnetically active and SO3H-functionalized ordered mesoporous resin and carbon (MOMR-SO3H, MOMC-SO3H) were successfully prepared by high-temperature hydrothermal synthesis from resol, copolymer surfactant, and iron cations at 180 °C, followed by sulfonation from sulfuric acid fuming. X-ray diffraction patterns show that MOMR-SO3H and MOMC-SO3H have ordered hexagonal mesoporous symmetry. N 2 isotherms indicate that these samples have uniform and opened mesopores, high surface areas (335-591 m2/g), and large pore volumes (0.34-0.35 cm3/g). Transmission electron microscopy shows that iron nanoparticles, which are superparamagnetic in nature, are highly dispersed in MOMC-SO3H sample. Catalytic tests show that MOMC-SO3H is highly active and excellently recyclable in esterification of acetic acid with butanol, esterification of acetic acid with cyclohexanol, and condensation of benzaldehyde with ethylene glycol. More interestingly, MOMC-SO3H catalyst is magnetically active, showing potential applications for separating catalysts by a magnetic field in the future.
Studies on a Synthesis of (RS)-Mevalonic Acid Lactone
Bardshiri, Esfandiar,Simpson, Thomas J.,Scott, A. Ian,Shishido, Kozo
, p. 1765 - 1767 (1984)
Full details of a high yielding synthesis of mevalonic acid lactone (1) which is of particular value in the preparation of 3- and/or 3'-labelled compounds are described.The key step, conversion of 3-hydroxy-3-methylpentane-1,5-dioic acid (3) into 3-hydroxy-3-methylpentane-1,5-dioic anhydride (4) using acetic anhydride, has been fully investigated, and an additional method using acetyl chloride and triethylamine is described.
Calibration-free estimates of batch process yields and detection of process upsets using in situ spectroscopic measurements and nonisothermal kinetic models: 4-(Dimethylamino)pyridine-catalyzed esterification of butanol
Gemperline, Paul,Puxty, Graeme,Maeder, Marcel,Walker, Dwight,Tarczynski, Frank,Bosserman, Mary
, p. 2575 - 2582 (2004)
The use of an near-IR fiber-optic spectrometer with a high-speed diode array for calibration-free monitoring and modeling of the reaction of acetic anhydride with butanol using the catalyst 4-(dimethylamino)pyridine in a microscale batch reactor was presented. Nonlinear fitting of a first-principles model directly to the reaction spectra gave calibration-free estimates of time-dependent concentration profiles and pure component spectra. Real-time modeling of a batch reaction could be achieved by augmenting prerun batch data with recently acquired spectral data followed by fitting of a multiway kinetic model. In real-time applications, accurate initial guesses of the parameter estimates from prerun data can be used to facilitate rapid convergence of the iterative nonlinear fitting process.
Efficient synthesis of vitamin e intermediate by lipase-catalyzed regioselective transesterification
Wei, Chun,Fu, Xian-Feng,Wang, Zhao,Yu, Xin-Jun,Zhang, Yin-Jun,Zheng, Jian-Yong
, p. 90 - 94 (2014)
Trimethylhydroquinone-1-monoacetate (TMHQ-1-MA) is a valuable synthetic intermediate for vitamin E acetate. Immobilized Lipozyme RM IM from Mucor miehei was shown to be the best biocatalyst for the production of TMHQ-1-MA through regioselective transesterification between trimethylhydroquinone diacetate (TMHQ-DA) and alcohol. The effects of lipase-catalyzed reaction conditions including solvent, acyl receptor, substrate mole ratio, reaction temperature and agitation speed were investigated. The optimum conditions for Lipozyme RM IM catalyzed regioselective transesterification were achieved at a substrate mole ratio of 1:1, an agitation of 200 rpm at 50 °C in MTBE/n-hexane (3:7). Under the above conditions, Lipozyme RM IM exhibited high substrate tolerance (substrate concentrations of 1.06 M). Recycling experiments demonstrated that Lipozyme RM IM was quite steady under the reaction conditions. The analysis of kinetic experiment showed that the enzymatic reaction obeys the Ping-Pong bi-bi mechanism with n-butanol inhibition.
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Leyes,Othmer
, p. 968,969 (1945)
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Esterification of acetic acid with butanol over sulfonic acid-functionalized hybrid silicas
Testa, Maria Luisa,La Parola, Valeria,Venezia, Anna Maria
, p. 109 - 113 (2010)
Sulfonic acid-functionalized hybrid silicas with different loading of organic moieties were synthesized by grafting and co-condensation followed by oxidation of the precursor thiol groups with hydrogen peroxide or by in situ oxidation methods involving the oxidation by hydrogen peroxide during the condensation reaction. As determined by photoelectron spectroscopy (XPS) complete oxidation of the thiol groups in the differently prepared materials was achieved at room temperature. In the esterification reaction of acetic acid with butanol the samples prepared by the in situ oxidation method exhibited the best catalytic activity. During recycling test with a selected sample, in spite of some sulfur leaching, stable activity was observed.
Alkyl substituted 4-N-oxazadisilinane cations: A new family of Si protic ionic liquids and its application on esterification reactions
Alhaddad, Maha,Chakraborty, Priyanka,Hu, Jinsong,Huang, Kuo-Wei
, (2020)
A series of oxazadisilinane compounds were prepared and used as Br?nsted bases to form a series of 21 siloxane protic ionic liquids (Si-PILs) with four different acids. This new family of Si-PILs were well characterized and examined to catalyze esterification reactions.
Thermodynamics of phase and chemical equilibrium in a strongly nonideal esterification system
Grob, Sascha,Hasse, Hans
, p. 92 - 101 (2005)
In this study, the reaction equilibrium of the reversible esterification of acetic acid with 1-butanol giving 1-butyl acetate and water was investigated. The entire composition space including the miscibility gap was covered at temperatures relevant for technical processes (353.15 K to 393.15 K). The experiments were carried out in a multiphase batch reactor with online gas chromatography and in a batch reactor with quantitative 1H NMR spectroscopy, respectively. The thermophysical database available in the literature was complemented by measurements of liquid-liquid and vapor-liquid equilibria. On the basis of that comprehensive data, thermodynamically consistent models of the reaction equilibrium were developed which predict the concentration dependence of the mass action law pseudoequilibrium constant, Kx. The following different modeling approaches are compared: the GE models NRTL and UNIQUAC as well as the PC-SAFT equation of state and the COSMO-RS model. All of them can successfully be used, the COSMO-RS model, however, has the highest predictive power.
Transesterification between Ethyl Acetate and n-Butanol in Compressed CO2 in the Critical Region of the Reaction System
Gao, Liang,Wu, Weize,Hou, Zhenshan,Jiang, Tao,Han, Buxing,Liu, Jun,Liu, Zhimin
, p. 13093 - 13099 (2003)
The phase behavior (KT) and the equilibrium constant (Kx) of the reaction system for the transesterification between ethyl acetate and n-butanol in compressed CO2 were studied systematically. The Kx was very sensitive to pressure as the reaction mixture approached the critical point (CP), bubble point (BP), and dew point (DP) in the critical region. The Kx increased significantly as the pressure approached the DP and CP, while it decreased as the pressure approached the BP, i.e., pressure had the opposite effect on the Kx in the subcritical region and in the supercritical region. The Peng-Robinson EOS could predict the Kx far from the critical region satisfactorily. However, the difference of the predicted results and the experimental data became larger as the reaction system approached the CP, BP, and DP in the critical region. The reaction could be carried out in the critical region with a suitable amount of CO2, whereas this was impossible without the solvent. Thus, the clean solvent could also be used as a green solvent to adjust the critical point and phase behaviors of the reaction system, so that the reaction could take place in the critical region, and the reaction could be tuned effectively by pressure.
Characterization and catalytic performance of basaltic dust as an efficient catalyst in the liquid-phase esterification of acetic acid with n-butanol
Said, Abd El-Aziz A.,Heikal, Mohamed Th. S.,Goda, Mohamed N.
, p. 725 - 733 (2019)
Three natural basaltic samples were collected and used as efficient catalysts for the liquid-phase synthesis of n-butyl acetate. The samples were characterized by X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), thermogravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and N2 sorption. The acidity of the samples was determined using isopropanol dehydration, and the strength of the acid sites was measured using chemisorption of basic probes. The catalytic activity of the samples towards the esterification of acetic acid with n-butanol was extensively examined. The influence of different parameters, such as the reaction refluxing time, molar ratio, catalyst loading, reusability, and calcination temperature, on the esterification reaction was studied in detail. The results revealed that all samples had high catalytic activity with a selectivity of 100% to n-butyl acetate formation. In addition, the sample obtained from the top hill of Volcano had the highest activity with a 80% yield of n-butyl acetate. Moreover, the significant catalytic performances were well correlated with the acidity of the samples and to the reaction rate constants.
Dehydrogenative ester synthesis from enol ethers and water with a ruthenium complex catalyzing two reactions in synergy
Ben-David, Yehoshoa,Diskin-Posner, Yael,Kar, Sayan,Luo, Jie,Milstein, David,Rauch, Michael
supporting information, p. 1481 - 1487 (2022/03/07)
We report the dehydrogenative synthesis of esters from enol ethers using water as the formal oxidant, catalyzed by a newly developed ruthenium acridine-based PNP(Ph)-type complex. Mechanistic experiments and density functional theory (DFT) studies suggest that an inner-sphere stepwise coupled reaction pathway is operational instead of a more intuitive outer-sphere tandem hydration-dehydrogenation pathway.
Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio-and Stereoselective Acylation of Alcohols
Koszelewski, Dominik,Brodzka, Anna,Madej, Arleta,Trzepizur, Damian,Ostaszewski, Ryszard
, p. 6331 - 6342 (2021/05/06)
Geminal diacetates have been used as sustainable acyl donors for enzymatic acylation of chiral and nonchiral alcohols. Especially, it was revealed that geminal diacetates showed higher reactivity than vinyl acetate for hydrolases that are sensitive to acetaldehyde. Under optimized conditions for enzymatic acylation, several synthetically relevant saturated and unsaturated acetates of various primary alcohols were obtained in very high yields up to 98% without E/Z isomerization of the double bond. Subsequently, the acyl donor was recreated from the resulting aldehyde and reused constantly in acylation. Therefore, the developed process is characterized by high atomic efficiency. Moreover, it was shown that acylation using geminal diacetates resulted in remarkable regioselectivity by discriminating among the primary and secondary hydroxyl groups in 1-phenyl-1,3-propanediol providing exclusively 3-acetoxy-1-phenyl-propan-1-ol in good yield. Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.