- 2-Quinoxalinol diamine Cu(II) complex: Facilitating catalytic oxidation through dual mechanisms
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The Cu(II) complex 1, Cu(II)-6-N-3,5-di-tert-butylsalicylidene-6,7- quinoxalinol-diamine, has been developed to address problems with current methods of catalytic oxidation using tert-butyl hydroperoxide (TBHP). Complex 1 demonstrated an increased capability to utilize TBHP while limiting interference from free radical reactions and was demonstrated to be highly effective in the oxidations of a variety of olefins. the Partner Organisations 2014.
- Li, Yuancheng,Lee, Taebum,Weerasiri, Kushan,Wang, Tanyu,Buss, Emily E.,McKee, Michael L.,Gorden, Anne E. V.
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- Pd-diimine: A highly selective catalyst system for the base-free oxidative heck reaction
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Pd(OAc)2/3 is an efficient catalyst system for the base-free oxidative Heck reaction that outperforms the currently available catalysts for the more challenging substrates studied. The catalyst system is highly selective, and works at room temperature with dioxygen as the oxidant.
- Gottumukkala, Aditya L.,Teichert, Johannes F.,Heijnen, Dorus,Eisink, Niek,Van Dijk, Simon,Ferrer, Catalina,Van Den Hoogenband, Adri,Minnaard, Adriaan J.
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- Copper-catalyzed aerobic oxidative rearrangement of tertiary allylic alcohols mediated by TEMPO
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A mild method for the oxidative rearrangement of tertiary allylic alcohols to β-substituted enones using a TEMPO/CuCl2 system, in the presence of molecular sieves, is described. Depending on the substrate, CuCl2 was used in either a catalytic amount under an oxygen atmosphere or stoichiometrically. Georg Thieme Verlag Stuttgart.
- Vatèle, Jean-Michel
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- A new dirhodium tetraacetate carbenoid: Synthesis, crystal structure and catalytic application
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A new dirhodium tetraacetate II involving 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene I was synthesized and characterized by general spectroscopic tools in the solution state as well as single X-ray crystallographic analysis in the solid state. The catalytic activity of dirhodium tetraacetate carbenoid II was tested for the allylic oxidation, and the improved reactivity to the allylic oxidation was observed compared to that of Rh2(OAc)4. The different electrochemical properties of dirhodium tetraacetate carbenoid II and Rh2(OAc)4 were compared via cyclic voltammetry.
- Na, Sung Jae,Lee, Bun Yeoul,Bui, Nhat-Nguyen,Mho, Sun-il,Jang, Hye-Young
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- Mild manganese(III) acetate catalyzed allylic oxidation: Application to simple and complex alkenes
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Manganese(III) acetate catalyzed allylic oxidation of alkenes to the corresponding enones was investigated, showing excellent regioselectivity and chemoselectivity (functional group compatibility). Δ5-Steroids were transformed into bioactive Δ5-en-7-ones under a nitrogen atmosphere, whereas simple alkenes were converted into the corresponding enones under an oxygen atmosphere in good yields.
- Shing, Tony K. M.,Yeung, Ying-Yeung,Su, Pak L.
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- A Method for the Cyclic Enone Synthesis Using Lithium Chloride-Hexamethylphosphoramide System
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Cyclic enones were obtained from the reactions of β-keto esters with acyclic α,β-unsaturated ketones by using lithium chloride in hexamethylphosphoramide.The products were brought via the Michael addition, decarboxylation, and the aldol condensation.
- Ozaki, Yutaka,Kubo, Ayako,Kim, Sang-Won
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- Palladium-catalyzed conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds and nitroalkenes
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The addition of aryltrialkoxysilanes to α,β-unsaturated carbonyl compounds (ketones, aldehydes) and nitroalkenes in the presence of SbCl3, TBAF, AcOH, and a catalytic amount of Pd(OAc)2, in CH3CN at 60 °C, provides the corresponding conjugate addition products in moderate to good yields. The addition of equimolar amounts of SbCl3 and TBAF is necessary for this reaction to proceed smoothly. The arylpalladium complex, which is generated by the transmetalation from a putative hypercoordinate silicon compound, is considered to be the catalytically active species.
- Denmark, Scott E.,Amishiro, Nobuyoshi
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- Allylic C-H activations using Cu(II) 2-quinoxalinol salen and tert-butyl hydroperoxide
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Using a Cu(II) 2-quinoxalinol salen complex as the catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant, allylic activations of olefin substrates can be converted to the corresponding enones or 1,4-enediones. Excellent yields can be achieved (up to 99%) within a very short reaction time and with great tolerance for additional functional groups. Possible mechanistic pathways have been characterized using Raman spectroscopy, cyclic voltammetry, and theoretical calculations.
- Li, Yuancheng,Lee, Tae Bum,Wang, Tanyu,Gamble, Audrey V.,Gorden, Anne E. V.
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- Oxygen as single oxidant for two steps: Base-free one-pot Pd(ii)-catalyzed alcohol oxidation & arylation to halogen-intact β-aryl α,β-enones
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Using oxygen as the sole oxidant for two steps, we developed a new method to synthesize β-aryl α,β-enones by fine-tuning the Pd(ii)-catalyzed oxidation of allyl alcohol to subsequent arylation with arylboronic acids, arylboronic ester and aryltrifluoroborate salt. This one-pot green method does not require copper salt, base, and intermediate isolation. Halogen-bearing chalcones, dibenzylideneacetones and arylalkyl enones were synthesized in good yields. This journal is
- Vellakkaran, Mari,Andappan, Murugaiah M. S.,Nagaiah, Kommu
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- Tandem nucleophilic addition/fragmentation reactions and synthetic versatility of vinylogous acyl triflates
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A thorough analysis of the chemistry of vinylogous acyl triflates provides insight into important chemical processes and opens new directions in synthetic technology. Tandem nucleophilic addition/C-C bond cleaving fragmentation reactions of cyclic vinylogous acyl triflates 1 yield a variety of acyclic acetylenic compounds. Full details are disclosed herein. A wide array of nucleophiles, such as organolithium and Grignard reagents, lithium enolates and their analogues, hydride reagents, and lithium amides, are applied. The respective reactions produce ketones 2, 1,3-diketones and their analogues 3, alcohols 4, and amides 5. The present reactions are proposed to proceed through a 1,2-addition of the nucleophile to the carbonyl group of starting triflates 1 to form tetrahedral alkoxide intermediates C, followed by Grob-type fragmentation, which effects C-C bond cleavage to yield acyclic acetylenic compounds 2-5 and 7. The potent nucleofugacity of the triflate moiety is channeled through the σ-bond framework of 1, providing direct access to the fragmentation pathway without denying other typical reactions of cyclic vinylogous esters. The synthetic versatility of vinylogous acyl triflates, including functionalization reactions of the cyclic enone core (1 → 6 or 8), is also illustrated.
- Kamijo, Shin,Dudley, Gregory B.
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- Intramolecular aldol condensations: Rate and equilibrium constants
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Rate and equilibrium constants have been determined for both the aldol addition and the elimination steps in the intramolecular condensation reactions of 2,5-hexanedione, 2,6-heptanedione, 1-phenyl-1,5-hexanedione, and 5-oxohexanal. The overall thermodynamics are similar for cyclization of 2,5-hexanedione and 2,6-heptanedione; conversion of 2,5-hexanedione to the corresponding enone is actually more favorable, but the cyclization of 2,5-hexanedione is 2400 times slower than that of 2,6-heptanedione. As expected on the basis of intermolecular analogs, the addition step is less favorable and slower for 1-phenyl-1,5-hexanedione, and the addition step for 5-oxohexanal is more favorable though similar in rate to that for heptanedione. Detailed analysis of the kinetics and equilibrium for all of these compounds, as well as 2-(2-oxopropyl)benzaldehyde, in terms of Marcus theory, leads to the same intrinsic barriers for the intramolecular reactions as were seen previously for the intermolecular reactions. This means that rate constants for intramolecular aldol reactions should be predictable from the energetics of the reactions and that the effective molarity can be calculated. Methods for estimating thermodynamic quantities for reactants and products of these reactions have been examined.
- Guthrie,Guo
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- A MIMIC STUDY ON COENZYME-B12 USING ORGANOCOBALOXIMES. THE REARRANGEMENT OF 1-SUBSTITUTED-2-OXOCYCLOPENTYLMETHYL RADICAL
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The radical cleavage of the carbon-cobalt bond of 1-phenyl-2-oxocyclopentylmethyl cobaloxime (1) and 1-ethoxycarbonyl-2-oxocyclopentylmethyl cobaloxime (2) gave only 3-phenylcyclohex-2-enone (7) and 3-ethoxycarbonylcyclohex-2-enone (8), respectively, by acyl migration.This rearrangement may be a reasonable mimicry of the ester migration mediated by coenzyme-B12.
- Tada, Masaru,Miura, Kyo,Okabe, Masami,Seki, Shigetaka,Mizukami, Hideyuki
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- Enantioselective hydrogenation of enones with a hydroformylation catalyst
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Use of a typical rhodium precatalyst for hydroformylation results in the enantioselective hydrogenation of cyclic enones with up to 90% ee. Extensive screening of chiral ligands reveals the simple ligand Chiraphos as the best ligand, so far. The hydrogenation shows high chemoselectivity. Exclusive formation of saturated, chiral b-branched ketones is observed. It is proposed that the catalyst follows a frustrated hydroformylation pathway ("monohydride-based mechanism") and differs by that from the classical cationic Schrock-Osborn type rhodium precatalysts ("dihydride-based mechanism") for enantioselective hydrogenation. The catalyst operates under neat conditions and is easily recyclable by simply distilling off the reaction mixture and treatment with syn gas prior to hydrogenation.
- Scheuermann Nee Taylor, Caroline J.,Jaekel, Christoph
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- Synthesis and catalytic activities of PdII-phosphine complexes modified poly(ether imine) dendrimers
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In this paper, we report synthesis of new alkyldiphenyl phosphine ligand modified poly(ether imine) dendrimers up to the third generation. The phosphinated dendrimers were obtained by functional group transformations of the alcohols present at the periphery of the dendrimers to chloride, followed by phosphination using LiPPh2. The modification at the peripheries of the dendrimers was performed successfully to obtain up to 16 alkyl diphenylphosphines in the case of a third generation dendrimer, in good yields for each individual step. After phosphination, dendritic ligands were complexed with Pd(COD)Cl2 to give dendritic phosphine-PdII complexes. Both the ligands and the metal complexes were characterized by spectroscopic and spectrometric techniques including high-resolution mass spectral analysis for the lower generations. Evaluation of the catalytic efficacies of the dendrimer-PdII metal complexes in mediating a prototypical C-C bond forming reaction, namely the Heck reaction, was performed using various olefin substrates. While the substrate conversion lowered with catalyst in the order from monomer to third generation dendrimer, the second and third generation dendrimers themselves were found to exhibit significantly better catalytic activities than the monomer and the first generation dendrimer. Graphical abstract
- Krishna, Thatavarathy Rama,Jayaraman, Narayanaswamy
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- Antimony(III) chloride as an efficient catalyst for palladium-catalyzed hydrophenylation of α,β-unsaturated ketones and aldehydes
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A remarkable catalytic effect of antimony(III) chloride was disclosed in palladium-catalyzed hydrophenylation of α,β-unsaturated ketones and aldehydes (Michael-type conjugate addition) with sodium tetraphenylborate in acetic acid at 25°C.
- Cho, Chan Sik,Motofusa, Shin-Ichi,Uemura, Sakae
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- Scalable and sustainable electrochemical allylic C-H oxidation
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New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as € classics €. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact.
- Horn, Evan J.,Rosen, Brandon R.,Chen, Yong,Tang, Jiaze,Chen, Ke,Eastgate, Martin D.,Baran, Phil S.
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- Lewis acid promoted oxidative rearrangement of tertiary allylic alcohols with the PhIO/TEMPO system
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A mild and environmentally friendly method for Lewis acid catalyzed oxidative rearrangement of tertiary allylic alcohols to β-disubstituted enones by the TEMPO/PhIO system is described. Bismuth triflate was found to be the most efficient catalyst for the majority of the substrates tested except for tertiary vinyl carbinols which could be transformed to enals in fair yields only when Re2O7 was used as catalyst. A plausible mechanism for this oxidative rearrangement is discussed. Georg Thieme Verlag Stuttgart.
- Vatèle, Jean-Michel
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- Reaction of organolithium reagents with η5-pentadienyl iron complexes: Formation of σ,η3-iron complexes
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Reaction of organolithium reagents with η5-pentadienyl iron complex 4 occurs at the C2/C4 position of the π-system, generating σ,η3-iron complexes 5. Air oxidation of these σ,η3-iron complexes generates cyclohexenones. Rea
- McDaniel, Keith F.,Kracker II, Larry R.,Thamburaj, Parinbam K.
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- A New Catalytic Activity of Antimony(III) Chloride in Palladium(0)-Catalyzed Conjugate Addition of Aromatics to α,β-Unsaturated Ketones and Aldehydes with Sodium Tetraphenylborate and Arylboronic Acids
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A remarkable catalytic effect of antimony(III) chloride is disclosed in palladium(0)-catalyzed conjugate addition of aromatics to α,β-unsaturated ketones and aldehydes with sodium tetraphenylborate and arylboronic acids in acetic acid at 25 deg C.Several other metal chlorides such as AlCl3, SnCl4, AsCl3, TiCl4, FeCl3, MoCl5, and CeCl3 are also effective in some cases, but SbCl3 is the salt of choice.Two key steps are proposed for this reaction: one is the oxidative addition of a C-B bond to Pd(0) forming an arylpalladium species, and the other is the formation of an antimony enolate derived from the initial coordination of SbCl3 to the carbonyl oxygen of an organopalladium intermediate.
- Cho, Chan Sik,Motofusa, Shin-ichi,Ohe, Kouichi,Uemura, Sakae,Shim, Sang Chul
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- 1,4-Addition of Arylsiloxanes to Enones Catalyzed by Dicationic Palladium(II) Complexes in Aqueous Media
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Catalytic 1,4-addition of arylsiloxanes to enones was carried out at 75°C in the presence of a dicationic palladium(II) catalyst in aqueous 1,4-dioxane. A nitrile-free complex generated in situ from Pd(dba)2 and Cu(BF4)2 in the presence of dppe or dppben was recognized to be the best catalyst to achieve high yields for the representative enones and enals.
- Nishikata, Takashi,Yamamoto, Yasunori,Miyaura, Norio
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- Selective isomerization of electron deficient vinylcyclopropanes by thermal action of pentacarbonyl iron
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The response of a variety of vinylcyclopropanes, bearing an ester group in the β-position, upon exposure to pentacarbonyl iron at elevated temperaturees is established. Dienic esters with a single configuration of the double bonds are obtained by this route in high yield. Steric and electronic factors, governing the course of the reactions, were investigated using nitrile and alkyl substituted vinylcyclopropanes.
- Schulze, Matthias M.,Gockel, Ulrich
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- Cyclopropyl conjugation and ketyl anions: When do things begin to fall apart?
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Results pertaining to the electrochemical reduction of 1,2- diacetylcyclopropane (5), 1-acetyl-2-phenylcyclopropane (6), 1-acetyl-2-benzoylcyclopropane (7), and 1,2-dibenzoylcyclopropane (8) are reported. While 6?- exists as a discrete species, the barrier to ring opening is very small (107 s-1. For 7 and 8, the additional resonance stabilization afforded by the benzoyl moieties results in significantly lower rate constants for ring opening, on the order of 10 5-106 s-1. Electron transfer to 8 serves to initiate an unexpected vinylcyclopropane → cyclopentene type rearrangement, which occurs via a radical ion chain mechanism. The results for reduction of 5 are less clear-cut: The experimental results suggest that the reduction is unexceptional, with a symmetry coefficient α ≤ 0.5, and reorganization energy consistent with a simple electron-transfer process (one electron reduction, followed by ring opening). In contrast, molecular orbital calculations suggest that 5?- has no apparent lifetime and that reduction of 5 may occur by a concerted dissociative electron transfer (DET) mechanism (i.e., electron transfer and ring opening occur simultaneously). These seemingly contradictory results can be reconciled if the increase in the internal reorganization energy associated with the onset of concerted DET is offset by a lowering of the solvent reorganization energy associated with electron transfer to a more highly delocalized LUMO.
- Tanko,Li, Xiangzhong,Chahma, M'Hamed,Jackson, Woodward F.,Spencer, Jared N.
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- Continuous-Flow Synthesis of meta-Substituted Phenol Derivatives
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Two complementary microreactor technologies were developed for the study of biphasic gas-liquid reactions and preparation of meta-substituted phenol derivatives. The first capillary microreactor, composed of a T-junction and simple capillary, enabled oxidative Heck/dehydrogenation on a microgram scale with a shortened reaction time; the total sequence time for oxidative Heck/dehydrogenation reactions was optimized from 2160 min in a traditional batch system to 130 min in the microchemical system. The second tube-in-tube microreactor, composed of a gas-permeable inner tube and gas-nonpermeable outer tube, successfully performed a gram-scale synthesis under the optimized safety and economic conditions which were established from the first microgram-scale study. The two microreactors have great potential for exploring reactions involving gaseous and liquid reagents.
- Park, Jeong Hyeon,Park, Chan Yi,Kim, Mi Jin,Kim, Min Uk,Kim, Young Joon,Kim, Geon-Hee,Park, Chan Pil
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- One-pot β-substitution of enones with alkyl groups to β-alkyl enones
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Vinylic hydrogens at the β-position of enones were effectively substituted with alkyl groups in a one-pot procedure to afford β-alkyl enones in good to high isolated yields by conjugate addition of higher-order dialkyl cyanocuprates to enones, followed by a reaction with N-tert-butylbenzenesulfinimidoyl chloride at -78 °C. The Royal Society of Chemistry 2005.
- Matsuo, Jun-Ichi,Aizawa, Yayoi
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- Manganese/Bicarbonate-Catalyzed Epoxidation of Lipophilic Alkenes with Hydrogen Peroxide in Ionic Liquids
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(Equation presented) Effective epoxidation of lipophilic alkenes using hydrogen peroxide was accomplished with the manganese sulfate/bicarbonate catalytic system in an ionic liquid at room temperature.
- Tong, Kit-Ho,Wong, Kwok-Yin,Chan, Tak Hang
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- IBS-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with oxone
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A 2-iodoxybenzenesulfonic acid (IBS)-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with powdered Oxone in the presence of potassium carbonate and tetrabutylammonium hydrogen sulfate has been developed.
- Uyanik, Muhammet,Fukatsu, Ryota,Ishihara, Kazuaki
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- Allylic oxidation: Easy synthesis of alkenones from activated alkenes with TEMPO
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Activated alkenes and dienes are converted into the corresponding alkenone in excellent yields (>90%). In aqueous acetonitrile, the transformations are catalyzed by 2,2,6,6-tetramethyl-1-oxopiperidinium (TEMPO+) in the presence of water and 2,6-lutidine. TEMPO+ cations were regenerated electrochemically from the radical parent (TEMPO.) at a vitreous carbon anode.
- Breton, Tony,Liaigre, Denis,Belgsir, El Mustapha
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- Conjugate addition of aryl boronic acids to enones catalyzed by cationic palladium(II)-phosphane complexes
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A cationic palladium complex was found to be an efficient catalyst for the 1,4-addition of aryl boronic acids to enones at room temperature (see scheme; X= ClO4, OTf, BF4, PF6, or SbF6); Tf=trifluoromethanesulfonyl).
- Nishikata, Takashi,Yamamoto, Yasunori,Miyaura, Norio
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- Dirhodium(II) caprolactamate: An exceptional catalyst for allylic oxidation
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The oxidation of organic molecules represents a fundamentally important chemical process. Particularly important is allylic oxidation, whereby a single methylene unit is converted directly into a carbonyl group. In this communication, we report that dirhodium(II) caprolactamate [Rh2(cap)4] in combination with tert-butyl hydroperoxide (terminal oxidant) effectively catalyzes the allylic oxidation of a variety of olefins and enones. The reaction is completely selective, tolerant of air/moisture, and can be performed with as little as 0.1 mol % catalyst in minutes. A mechanistic proposal involving redox chain catalysis has been put forth, as well as evidence for the intermediacy of a higher valent dirhodium tert-butyl peroxy complex. Copyright
- Catino, Arthur J.,Forslund, Raymond E.,Doyle, Michael P.
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- A new method for the preparation of Michael adducts and cyclic enones using lithium chloride-hexamethylphosphoramide system
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A new procedure using lithium chloride in hexamethylphosphoramide was found to be useful for the synthesis of Michael-type adducts and cyclic enones. Selectivity for the two products could be controlled by altering the reaction temperature employed. The urea-type solvents were also examined instead of hexamethylphosphoramide.
- Ozaki,Kubo,Okamura,Kim
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- Ir(NHC)-Catalyzed Synthesis of β-Alkylated Alcohols via Borrowing Hydrogen Strategy: Influence of Bimetallic Structure
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Multi N-heterocyclic carbene(NHC)-modified iridium catalysts were employed in the β-alkylation of alcohols; dimerization of primary alcohols (Guerbet reaction), cross-coupling of secondary and primary alcohols, and intramolecular cyclization of alcohols. Mechanistic studies of Guerbet reaction, including kinetic experiments, mass analysis, and density functional theory (DFT) calculation, were employed to explain the fast reaction promoted by bimetallic catalysts, and the dramatic reactivity increase of monometallic catalysts at the late stage of the reaction. (Figure presented.).
- Sung, Kihyuk,Lee, Mi-hyun,Cheong, Yeon-Joo,Kim, Yu Kwon,Yu, Sungju,Jang, Hye-Young
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p. 3090 - 3097
(2021/05/10)
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- Palladium mediated one-pot synthesis of 3-aryl-cyclohexenones and 1,5-diketones from allyl alcohols and aryl ketones
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One-pot synthesis of Robinson annulated 3-aryl-cyclohexenones from allyl alcohols and ketones using palladium is reported. Long chain aliphatic or aryl substitutions at the C1 position of allyl alcohol result in the formation of 1,5-diketone products. This simple one-pot method avoids the use of highly electrophilic vinyl ketones.
- Samser, Shaikh,Biswal, Priyabrata,Meher, Sushanta Kumar,Venkatasubbaiah, Krishnan
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p. 1386 - 1394
(2021/02/27)
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- Copper-Catalyzed Enantioselective 1,2-Reduction of Cycloalkenones
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We report an asymmetric 1,2-reduction of cyclic α,β-unsaturated ketones to access various enantiomerically enriched cyclic allylic alcohols under mild conditions, catalyzed by in situ generated copper hydride ligated with (R)-DTBM-C3*-TunePhos. α-Brominated cycloalkenones were reduced with excellent enantioselectivities of up to 98% ee, while substrates that were without α-substituents were reduced chemoselectively, with moderate enantioselectivities.
- Shi, Yongjie,Wang, Jingxin,Yin, Qin,Zhang, Xumu,Chiu, Pauline
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supporting information
p. 5658 - 5663
(2021/08/01)
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- Enantioselective Hydrogenation of Endocyclic Enones: the Solution to a Historical Problem?
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The enantioselective hydrogenation of endocyclic enones has been a historical problem for homogeneous catalysis. We herein report an efficient method to reduce endocyclic enones with molecular hydrogen. Catalyzed by a rhodium/Zhaophos complex, a variety of enones with five-, six- or seven-member ring were hydrogenated with high enantioselectivity (92%—99% ee). Excellent chemo- and enantioselectivity demonstrated this method was successfully applied in the enantioselective hydrogenation of citral to produce enantio-enriched citronellal.
- Lang, Qiwei,Yang, Huaxin,Gu, Guoxian,Feng, Qiang,Wen, Jialin,Zhang, Xumu
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supporting information
p. 933 - 936
(2021/03/03)
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- A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles
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A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.
- Rossi-Fernández, Lucía,Dorn, Viviana,Radivoy, Gabriel
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supporting information
p. 519 - 526
(2021/03/31)
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- Palladium-Catalyzed Cross-Coupling of Alkenyl Carboxylates
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Carboxylate esters have many desirable features as electrophiles for catalytic cross-coupling: they are easy to access, robust during multistep synthesis, and mass-efficient in coupling reactions. Alkenyl carboxylates, a class of readily prepared non-aromatic electrophiles, remain difficult to functionalize through cross-coupling. We demonstrate that Pd catalysis is effective for coupling electron-deficient alkenyl carboxylates with arylboronic acids in the absence of base or oxidants. Furthermore, these reactions can proceed by two distinct mechanisms for C?O bond activation. A Pd0/II catalytic cycle is viable when using a Pd0 precatalyst, with turnover-limiting C?O oxidative addition; however, an alternative pathway that involves alkene carbopalladation and β-carboxyl elimination is proposed for PdII precatalysts. This work provides a clear path toward engaging myriad oxygen-based electrophiles in Pd-catalyzed cross-coupling.
- Becica, Joseph,Heath, Oliver R. J.,Leitch, David C.,Zheng, Cameron H. M.
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supporting information
p. 17277 - 17281
(2020/07/31)
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- Catalytic enantioselective total synthesis of (?)-ar-Tenuifolene
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First catalytic asymmetric total synthesis of aromatic sesquiterpene, (?)-ar-teunifolene (1) is featured (3 steps, 75% overall yields) from commercially available 3-methyl cyclohex-2-enone 16. The enantioenriched 3,3-disubstituted cyclohexanone 11 is obtained from Pd(II)-catalyzed enantioselective (p-tolyl)boronic acid addition to 3-methyl cyclohex-2-enone 16 in 90% ee, which is found to be the key intermediate. A diastereoselective methyllithium addition of this enantioenriched product followed by dehydration completes straightforward access to (?)-ar-teunifolene (1).
- Shaw, Kundan,Niyogi, Sovan,Bisai, Vishnumaya
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- CeO2-Supported Pd(II)-on-Au Nanoparticle Catalyst for Aerobic Selective α,β-Desaturation of Carbonyl Compounds Applicable to Cyclohexanones
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Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study, we designed an ideal CeO2-supported Pd(II)-on-Au nanoparticle catalyst (Pd/Au/CeO2) and successfully achieved heterogeneously catalyzed selective desaturation of cyclohexanones to cyclohexenones using O2 in air as the oxidant. Besides cyclohexenones, various bioactive enones can also be synthesized from the corresponding saturated ketones under open air conditions in the presence of Pd/Au/CeO2. Preliminary mechanistic studies revealed that α-C-H bond cleavage in the substrates is the turnover-limiting step of this desaturation reaction.
- Jin, Xiongjie,Mizuno, Noritaka,Takei, Daisuke,Yabe, Tomohiro,Yamaguchi, Kazuya,Yatabe, Takafumi
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p. 5057 - 5063
(2020/05/27)
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- Asymmetric Construction of Alkaloids by Employing a Key ω-Transaminase Cascade
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An ω-transaminase-triggered intramolecular aza-Michael reaction has been employed for the preparation of cyclic β-enaminones in good yield and excellent enantio- and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza-Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, this biocatalytic aza-Michael step was combined with annulation chemistry, affording unique stereo-defined fused alkaloid architectures.
- Taday, Freya,Ryan, James,Argent, Stephen P.,Caprio, Vittorio,Maciá, Beatriz,O'Reilly, Elaine
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supporting information
p. 3729 - 3732
(2020/03/11)
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- Arene Trifunctionalization with Highly Fused Ring Systems through a Domino Aryne Nucleophilic and Diels–Alder Cascade
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A convenient and efficient domino aryne process was developed under transition-metal-free conditions to generate a range of tetra- and pentacyclic ring systems. This transformation was realized via a 1,2-benzdiyne through a nucleophilic and Diels–Alder reaction cascade using styrene as the diene moiety. Three new chemical bonds, namely one C?N and two C?C bonds, and two benzofused rings could be constructed concomitantly, which was made possible by distinct chemoselective control at both the 1,2-aryne and 2,3-aryne stages. Moreover, in-depth studies were carried out on the domino aryne precursors and controlling the diastereoselectivity.
- He, Jia,Jia, Zizi,Tan, Hongcheng,Luo, Xiaohua,Qiu, Dachuan,Shi, Jiarong,Xu, Hai,Li, Yang
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supporting information
p. 18513 - 18518
(2019/11/19)
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- Intermolecular Multiple Dehydrogenative Cross-Couplings of Ketones with Boronic Acids and Amines via Copper Catalysis
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An efficient and versatile oxidative coupling reaction was developed for the synthesis of valuable β-functionalized unsaturated ketones and meta-substituted phenols. In the case of intramolecular reactions, achieving rapid molecular complexity through multiple dehydrogenative couplings is already a well-established strategy. Herein, we report an intermolecular multiple dehydrogenative coupling between ketones and nucleophilic amines or boronic acids using inexpensive copper(I) oxide as a catalyst. This method provides a facile access to highly desirable chemical products such as α,β-unsaturated ketones, enaminones, and synthetically relevant meta-substituted phenols. (Figure presented.).
- Wang, Tianzhang,Chen, Guowei,Lu, Yu-Jing,Chen, Qian,Huo, Yanping,Li, Xianwei
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supporting information
p. 3886 - 3892
(2019/07/19)
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- Palladium-Mediated Remote Functionalization in γ- And ?-Arylations and Alkenylations of Unblocked Cyclic Enones
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We report herein an extensive investigation of simple and regioselective endo- as well as exo-γ-arylations of silyl-dienol ethers of unblocked cyclic enones with the utilization of palladium-catalyzed, modified Kuwajima-Urabe conditions. We have also successfully explored a new exo-?-arylation of silyl-trienol ethers of π-extended cyclic enones. In addition, we also report, herein, exclusive γ- and ?-alkenylation of silyl-dienol and silyl-trienol ethers of cyclic enones.
- Saini, Gaurav,Mondal, Arpan,Kapur, Manmohan
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supporting information
p. 9071 - 9075
(2019/11/14)
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- Synthesis of chiral seven-membered β-substituted lactams: Via Rh-catalyzed asymmetric hydrogenation
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Rh/bisphosphine-thiourea ligand (ZhaoPhos)-catalyzed asymmetric hydrogenation of seven-membered β-substituted α,β-unsaturated lactams was successfully developed to prepare various chiral seven-membered β-substituted lactams with good to excellent results (up to >99% conversion, 99% yield, and >99% ee).
- Huang, Yi,Li, Pan,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 8819 - 8823
(2018/11/30)
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- An Electrophilic Trifluoromethylthiolation of Silylenol Ethers and β-Naphthols with Diethylaminosulfur Trifluoride and (Trifluoromethyl)trimethylsilane
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An efficient and general trifluoromethylthiolation of silylenol ethers and β-naphthols have been accomplished employing the combination of diethylaminosulfur trifluoride (DAST) and (trifluoromethyl)trimethylsilane (CF3TMS) as source of electrophilic trifluoromethylthio moiety for the synthesis of α-trifluoromethylthiolated carbonyl compounds and β-naphthols in good yields. Important features of this method include wide functional group tolerance and use of readily available DAST/CF3TMS. Potential of the methodology was demonstrated via the synthesis of α-trifluoromethylthiolated (+)-4-cholesten-3-one and naphthoquinone. (Figure presented.).
- Saravanan, Perumal,Anbarasan, Pazhamalai
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supporting information
p. 2894 - 2899
(2018/08/17)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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p. 3677 - 3686
(2018/06/04)
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- Convenient Access to meta-Substituted Phenols by Palladium-Catalyzed Suzuki–Miyaura Cross-Coupling and Oxidation
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We report a new approach to the synthesis of meta-substituted phenols in which a single palladium catalyst accomplishes a Suzuki–Miyaura cross-coupling between a β-chlorocyclohexenone and an arylboronic acid, and oxidation of the resulting cyclohexenone to the corresponding phenol upon introduction of a terminal oxidant and electron transfer mediator. Notably, this method also allows ready access to ortho, meta-disubstituted phenols, sterically congested biaryl phenols, and more highly substituted phenols.
- Wang, Zi,Orellana, Arturo
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supporting information
p. 11445 - 11449
(2017/08/26)
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- Palladium-Catalyzed Direct β-C?H Arylation of Ketones with Arylboronic Acids in Water
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A palladium-catalyzed direct β-C?H arylation of ketones was developed under mild conditions in water, featuring commercially available arylboronic acids as nucleophilic aryl sources and o-iodoxybenzoic acid as the oxidant. The method provides a concise route to access β-arylated ketones. Preliminary studies indicated that direct asymmetric β-C?H arylation of ketones could be achieved by this strategy. (Figure presented.).
- Hu, Xiaoyun,Yang, Xiaobo,Dai, Xi-Jie,Li, Chao-Jun
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p. 2402 - 2406
(2017/07/22)
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- Fe2(CO)9-mediated [5+1] cycloaddition of vinylcyclopropanes and CO for the synthesis of α, β-cyclohexenones
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A Fe2(CO)9-mediated [5+1] cycloaddition of vinylcyclopropanes (VCPs) and CO to α, β-cyclohexenones has been developed. The reaction can tolerate aryl and aliphatic groups at the α-position of VCPs, while VCP substrates with vinyl or alkynyl substitutions are not suitable ones. In addition, this reaction can also be used to synthesize bicyclic rings if an aryl group is attached to the vinyl moiety of the substrate. Compared to the Fe(CO)5-mediated [5+1] reaction, the use of cheap and safe Fe2(CO)9 and abandoning the photo-irradiation conditions are the two major advantages of the present method.
- Liu, Cheng-Hang,Zhuang, Zhe,Bose, Sritama,Yu, Zhi-Xiang
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supporting information
p. 2752 - 2755
(2016/05/19)
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- A highly efficient metal-free approach to: Meta - And multiple-substituted phenols via a simple oxidation of cyclohexenones
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A novel and efficient metal-free approach to substituted phenols has been disclosed from simple and readily available cyclohexenones and cyclohexenone equivalents. Dimethyl sulfoxide (DMSO), a simple and common organic reagent, was employed as a mild oxidant in this I2-catalysis, which significantly tolerates various substituents including some easily oxidizable or reducible functionalities. The challenging meta- and multiple-substituted phenols could be well prepared by this method. The metal-free and mild oxidation make this protocol very simple, practical, and easy to handle.
- Liang, Yu-Feng,Song, Song,Ai, Lingsheng,Li, Xinwei,Jiao, Ning
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supporting information
p. 6462 - 6467
(2018/06/08)
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- Preparation Method for Meta-Substituted Phenol by Oxidative Heck/Dehydrogenation in Microchannel
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The present invention relates to a method for efficiently carrying out oxidative Heck/dehydrogenation, which, otherwise, is difficult to be applied to actual production due to an excessively slow reaction rate, although it is useful for preparing a meta-substituted phenol. More particularly, the method for preparing a phenol derivative having a substituent at the meta-position from cyclohexanone through oxidative Heck/dehydrogenation comprises the steps of: (A) introducing cyclohexanone, a boric acid derivative, palladium catalyst and oxygen to a microchannel having a width of 0.1-4.0 mm and carrying out a reaction; (B) further adding tetrafluoroacetic acid (TFA) to the microchannel having a width of 0.1-4.0 mm and including the reaction mixture, while supplying oxygen continuously thereto, and continuously carrying out a reaction.
- -
-
Paragraph 0041-0045
(2017/05/02)
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- Synthesis of β-Substituted Cyclic Enones via Phosphonium Salt-Activated, Palladium-Catalyzed Cross-Coupling of Cyclic 1,3-Diones
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Phosphonium salt-activated, Pd-catalyzed Suzuki-Miyaura and Sonogashira cross-coupling reactions of cyclic 1,3-diones in the synthesis of β-substituted cyclic enones are described. These transformations exhibit good isolated yield and high generality with respect to both substrates and coupling partners. Extension of the substrate scope to cyclic 1,3-dione equivalents, such as 2-cyanocyclohexanone (4), is also briefly examined.
- Yang, Shyh-Ming,Kuo, Gee-Hong,Gaul, Michael D.,Murray, William V.
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p. 3464 - 3469
(2016/05/19)
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- Fe3O4 magnetic nanoparticles (MNPs) as an efficient catalyst for selective oxidation of benzylic and allylic C-H bonds to carbonyl compounds with tert-butyl hydroperoxide
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Fe3O4 magnetic nanoparticles (MNPs) were prepared by a co-precipitation method with oleic acid as a surfactant and characterized by FT-IR, TEM, DLS, XRD, VSM techniques. XRD, DLS and TEM analysis of this catalyst clearly showed the formation of cubic structure Fe3O4 MNPs, with a mean size of 16 nm. Moreover, a magnetization measurement revealed that the Fe3O4 MNPs had superparamagnetic behaviour and the saturation magnetization of the catalyst was 54.6 emu g-1. The Fe3O4 MNPs in combination with tert-butyl hydroperoxide catalyzed the oxidation of various benzylic and allylic C-H bonds to the corresponding carbonyl compounds in excellent yields. These oxidation reactions were effectively and economically performed under mild conditions, and therefore the dual challenge of cost effectiveness and benign nature of the processes was met.
- Zarghani, Monireh,Akhlaghinia, Batool
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p. 38592 - 38601
(2016/05/24)
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- Copper/Selectfluor-System-Catalyzed Dehydration-Oxidation of Tertiary Cycloalcohols: Access to β-Substituted Cyclohex-2-enones, 4-Arylcoumarins, and Biaryls
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A route to β-substituted cyclohex-2-enones, 4-arylcoumarins, and biaryls has been developed. This approach involves a one-pot Cu0/Selectfluor-catalyzed dehydration-oxidation of tertiary cycloalcohols. Thus, by using 2 equiv. of Selectfluor at 25 C, the dehydration-oxidation of tertiary cyclohexanols and oxabenzocyclohexanols gave β-substituted cyclohex-2-enones and 4-arylcoumarins, respectively; whereas the dehydration-oxidation of tertiary cyclohexanols gave biaryls as the final products by using 2.5 equiv. of Selectfluor at 80 C. A route to β-substituted cyclohex-2-enones, 4-arylcoumarins, and biaryls has been developed. This approach involves a one-pot Cu0/Selectfluor-catalyzed dehydration-oxidation of tertiary cycloalcohols.
- Ren, Shaobo,Zhang, Jian,Zhang, Jiahui,Wang, Heng,Zhang, Wei,Liu, Yunkui,Liu, Miaochang
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p. 5381 - 5388
(2015/08/24)
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- Allylic and benzylic sp3 C-H oxidation in water
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A copper-catalyzed method for the oxidation of allylic and benzylic sp3 C-H by aqueous tert-butyl hydroperoxide (T-Hydro) in water using a recyclable fluorous ligand has been developed. The reaction procedure is tolerant to additional functional groups and the fluorous ligand could be reused with little loss of catalytic activity. This journal is
- Ang, Wei Jie,Lam, Yulin
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p. 1048 - 1052
(2015/03/04)
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- Fluorous bispidine: A bifunctional reagent for copper-catalyzed oxidation and knoevenagel condensation reactions in water
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Fluorous bispidine-type ligands have been developed to facilitate its recovery and reusability and to demonstrate its bifunctional property as a ligand and base in copper-catalyzed aerobic oxidation, the Knoevenagel condensation and tandem oxidation/Knoevenagel condensation in water under mild conditions. Application of the fluorous ligand was also extended to the surfactant-free copper-catalyzed allylic and benzylic sp3 C-H oxidation reaction in water. The fluorous ligands could be recovered using F-SPE with recovery ranging from 91-97% and could be reused five times with little loss of activity.
- Ang, Wei Jie,Chng, Yong Sheng,Lam, Yulin
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p. 81415 - 81428
(2015/10/06)
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- Novel PDC catalyzed oxidative rearrangement of tertiary allylic alcohols to β-substituted enones
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Novel pyridinium dichromate (PDC) catalyzed oxidative rearrangement for the conversion of tertiary allylic alcohols to ?-substituted enones is described. Using a catalytic amount of PDC with PhI(OAc)2 as a co-oxidant in the presence of magnesium sulfate and water under oxygen was found effective for this rearrangement.
- Matsunaga, Kazuma,Hirajima, Hironori,Kishida, Atsushi,Takatori, Kazuhiko,Nagaoka, Hiroto
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p. 5941 - 5944
(2015/11/02)
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- Isopropylmagnesium chloride-promoted unilateral addition of Grignard reagents to β-diketones: One-pot syntheses of β-tertiary hydroxyl ketones or 3-substituted cyclic-2-enones
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The regioselective unilateral additions of Grignard reagents to acyclic or cyclic β-diketones were effectively promoted by sub-stoichiometric amounts of i-PrMgCl to afford β-tertiary hydroxyl ketones or 3-substituted cyclic-2-enones, respectively. Also, the addition of Grignard reagents to acyclic β-diketones followed by a reaction with cyclic β-diketones in a one-pot process was put forward. The reaction mechanism was discussed in detail to explain the high regioselectivity via chemical experiments, hydrogen-deuterium exchange and mass spectrometry.
- Yuan, Rui,Zhao, Dan,Zhang, Li-Yuan,Pan, Xiang,Yang, Yan,Wang, Pei,Li, Hong-Feng,Da, Chao-Shan
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supporting information
p. 724 - 728
(2016/01/12)
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- Highly enantioselective synthesis of chiral cyclic allylic amines via RH-catalyzed asymmetric hydrogenation
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Highly regioselective and enantioselective asymmetric hydrogenation of cyclic dienamides catalyzed by an Rh-DuanPhos complex has been developed, which provides a readily accessible method for the synthesis of chiral cyclic allylic amines in excellent enantioselectivities (up to 99% ee). The products are valuable chiral building blocks and could be easily transformed to multisubstituted cyclohexane derivatives.
- Zhou, Ming,Liu, Tang-Lin,Cao, Min,Xue, Zejian,Lv, Hui,Zhang, Xumu
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supporting information
p. 3484 - 3487
(2014/07/21)
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- Palladium-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with oxygen in aqueous solvent
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A one-pot procedure for Pd(TFA)2-catalyzed 1,3-isomerization of tertiary allylic alcohols to secondary allylic alcohols followed by a Pd(TFA)2/neocuproine-catalyzed oxidative reaction to β-disubstituted-α,β-unsaturated kenones was developed. (Chemical Equation Presented).
- Li, Jingjie,Tan, Ceheng,Gong, Jianxian,Yang, Zhen
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p. 5370 - 5373
(2015/01/09)
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- Mechanistic insights into palladium leaching in novel Pd/C-catalyzed boron-heck reaction of arylboronic acid
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For the first time, Pd/C has been used for the Boron-Heck reaction, and the detailed mechanistic aspects of the reaction have been proven experimentally by a leaching test as well as by cyclic voltammetry studies. The results indicate that palladium leaching as a Pd(II) species, by oxidative addition of the arylboronic acid, is responsible for the reaction. Georg Thieme Verlag Stuttgart - New York.
- Dighe, Mahesh G.,Lonkar, Sachin L.,Degani, Mariam S.
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p. 347 - 350
(2013/04/23)
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- Aerobic oxidative heck/dehydrogenation reactions of cyclohexenones: Efficient access to meta-substituted phenols
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Jockeying for the (meta)position: A new dicationic palladium(II) catalyst, employing a 6,6′-dimethyl-2,2′-bipyridine ligand, promotes both the aerobic oxidative Heck coupling and dehydrogenation reactions of cyclohexenones. These reactions may be combined in a one-pot sequence to enable the straightforward synthesis of meta-substituted phenols (see scheme). Copyright
- Izawa, Yusuke,Zheng, Changwu,Stahl, Shannon S.
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supporting information
p. 3672 - 3675
(2013/04/23)
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- Enzyme- and ruthenium-catalyzed dynamic kinetic resolution of functionalized cyclic allylic alcohols
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Enantioselective synthesis of functionalized cyclic allylic alcohols via dynamic kinetic resolution has been developed. Cyclopentadienylruthenium catalysts were used for the racemization, and lipase PS-IM or CALB was employed for the resolution. By optimization of the reaction conditions the formation of the enone byproduct was minimized, making it possible to prepare a range of optically active functionalized allylic alcohols in good yields and high ee's.
- Lihammar, Richard,Millet, Renaud,Baeckvall, Jan-E.
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p. 12114 - 12120
(2014/01/06)
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- Ligand- and base-free Pd(II)-catalyzed controlled switching between oxidative heck and conjugate addition reactions
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A simple change of solvent allows controlled and efficient switching between oxidative Heck and conjugate addition reactions on cyclic Michael acceptor substrates, catalyzed by a cationic Pd(II) catalyst system. Both reactions are ligand- and base-free and tolerant of air and moisture, and the controlled switching sheds light on some of the factors which favor one reaction over the other.
- Walker, Sarah E.,Boehnke, Julian,Glen, Pauline E.,Levey, Steven,Patrick, Lisa,Jordan-Hore, James A.,Lee, Ai-Lan
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supporting information
p. 1886 - 1889
(2013/06/04)
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- Discovery of disubstituted piperidines and homopiperidines as potent dual NK1 receptor antagonists-serotonin reuptake transporter inhibitors for the treatment of depression
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This report describes the synthesis, structure-activity relationships and activity of piperidine, homopiperidine, and azocane derivatives combining NK1 receptor (NK1R) antagonism and serotonin reuptake transporter (SERT) inhibition. Our studies culminated in the discovery of piperidine 2 and homopiperidine 8 as potent dual NK1R antagonists-SERT inhibitors. Compound 2 demonstrated significant activity in the gerbil forced swimming test, suggesting that dual NK1R antagonists-SERT inhibitors may be useful in treating depression disorders.
- Wu, Yong-Jin,He, Huan,Bertekap, Robert,Westphal, Ryan,Lelas, Snjezana,Newton, Amy,Wallace, Tanya,Taber, Matthew,Davis, Carl,MacOr, John E.,Bronson, Joanne
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p. 2217 - 2228
(2013/05/08)
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- The cinchona primary amine-catalyzed asymmetric epoxidation and hydroperoxidation of α,β-unsaturated carbonyl compounds with hydrogen peroxide
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Using cinchona alkaloid-derived primary amines as catalysts and aqueous hydrogen peroxide as the oxidant, we have developed highly enantioselective Weitz-Scheffer-type epoxidation and hydroperoxidation reactions of α,β-unsaturated carbonyl compounds (up to 99.5:0.5 er). In this article, we present our full studies on this family of reactions, employing acyclic enones, 5-15-membered cyclic enones, and α-branched enals as substrates. In addition to an expanded scope, synthetic applications of the products are presented. We also report detailed mechanistic investigations of the catalytic intermediates, structure-activity relationships of the cinchona amine catalyst, and rationalization of the absolute stereoselectivity by NMR spectroscopic studies and DFT calculations.
- Lifchits, Olga,Mahlau, Manuel,Reisinger, Corinna M.,Lee, Anna,Fares, Christophe,Polyak, Iakov,Gopakumar, Gopinadhanpillai,Thiel, Walter,List, Benjamin
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supporting information
p. 6677 - 6693
(2013/06/05)
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- Cyclometalation of anthyridine-based ligands with dirhodium acetates: Structure and catalytic activity
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Coordination of 2,8-Ar2-5-phenylanthyridines (Ar = 2-thienyl, 1a; Ar = 2-ClC6H4-, 1b) with dirhodium tetraacetate yielded the cyclometalated complexes [Rh2(OAc)3(metalated- 1a)] (3a) and [Rh2(OAc)3(metalated-1b)] (3b), respectively. Under acidic conditions, cleavage of the Rh-C bond in 3a,b took place to give the corresponding coordination complexes 4a,b. Treatment of 3a,b with PPh3 led to the phosphine-cyclometalated species [Rh 2(OAc)2{P,C-(C6H4)PPh 2}(metalated-1a)] (5a) and [Rh2(OAc)2{P,C- (C6H4)PPh2}(metalated-1b)] (5b), respectively. These new dirhodium complexes have been structurally characterized by NMR spectroscopy, and some representative compounds were also analyzed by X-ray methods. The use of these newly prepared dirhodium complexes as catalysts for the allylic oxidation of cyclohexenes was investigated.
- Huang, Da-Wei,Lo, Ying-Hao,Liu, Yi-Hung,Peng, Shie-Ming,Liu, Shiuh-Tzung
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p. 4009 - 4015
(2013/08/23)
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- Pt-catalyzed oxidative rearrangement of cyclic tertiary allylic alcohols to enones using aqueous hydrogen peroxide
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An oxidative rearrangement of cyclic tertiary allylic alcohols to β-disubstituted α,β-unsaturated ketones by Pt black catalyst with aqueous hydrogen peroxide is described. The reaction proceeds under organic solvent- and halide-free conditions and gives only water as a coproduct. The Pt black catalyst is commercially available and can be reused at least four times.
- Nagamine, Takashi,Kon, Yoshihiro,Sato, Kazuhiko
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p. 744 - 746
(2012/09/22)
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- Enantioselective synthesis of (-)-CP-55940 via ruthenium-catalyzed asymmetric hydrogenation of ketones
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A new and efficient catalytic asymmetric synthesis of the potent cannabinoid receptor agonist (-)-CP-55940 has been developed by using ruthenium-catalyzed asymmetric hydrogenation of racemic α-aryl ketones via dynamic kinetic resolution (DKR) as a key step. With RuCl2-SDPs/ diamine [SDPs=7,7'-bis(diarylphophino)-1,1'-spirobiindane] catalysts the asymmetric hydrogenation of racemic α-arylcyclohexanones via DKR provided the corresponding cis-β-arylcyclohexanols in high yields with up to 99.3% ee and >99:1 cis-selectivities. Both ethylene ketal group at the cyclohexane ring and ortho-methoxy group at the phenyl ring of the substrates 6 have little effect on the selectivity and reactivity of the hydrogenations. Based on this highly efficient asymmetric ketone hydrogenation, (-)-CP-55940 was synthesized in 13 steps (the longest linear steps) in 14.6% overall yield starting from commercially available 3-methoxybenzaldehyde and 1,4-cyclohexenedione monoethylene acetal. Copyright
- Cheng, Li-Jie,Xie, Jian-Hua,Wang, Li-Xin,Zhou, Qi-Lin
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supporting information; experimental part
p. 1105 - 1113
(2012/05/21)
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- Rh(I)-catalyzed [5 + 1] cycloaddition of vinylcyclopropanes and CO for the synthesis of α,β- and β,γ-cyclohexenones
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A cationic Rh(I)-catalyzed [5 + 1] cycloaddition of vinylcyclopropanes and CO has been developed, affording either β,γ-cyclohexenones as major products or α,β-cyclohexenones exclusively, under different reaction conditions.
- Jiang, Guo-Jie,Fu, Xu-Fei,Li, Qian,Yu, Zhi-Xiang
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supporting information; experimental part
p. 692 - 695
(2012/03/26)
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- Oxidative conversion of silyl enol ethers to α,β-unsaturated ketones employing oxoammonium salts
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The oxidative conversion of silyl enol ethers to α,β-unsaturated ketones using a less-hindered class of oxoammonium salts (AZADO +BF4-) is described. The reaction proceeds via the ene-like addition of oxoammonium salts to silyl enol ethers.
- Hayashi, Masaki,Shibuya, Masatoshi,Iwabuchi, Yoshiharu
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supporting information; experimental part
p. 154 - 157
(2012/02/16)
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- Synthesis of cyclic enones via direct palladium-catalyzed aerobic dehydrogenation of ketones
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α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. Here, we report the discovery and application of Pd(DMSO)2(TFA)2 as a catalyst for direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O2 as the oxidant. The substrate scope includes heterocyclic ketones and several natural-product precursors.
- Diao, Tianning,Stahl, Shannon S.
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supporting information; experimental part
p. 14566 - 14569
(2011/10/17)
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- Room temperature nickel(II) complexes [(4-MeOC6H 4)Ni(PCy3)2OTs and Ni(PCy3) 2X2]-catalyzed cross-coupling reactions of aryl/alkenyl sulfonates with arylboronic acids
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Room temperature nickel(II) complexes [(4-MeOC6H 4)Ni(PCy3)2OTs and Ni(PCy3) 2X2 (X=Cl, Br)]-catalyzed cross-coupling reactions of aryl/alkenyl sulfonates with arylboronic acids are described. The nickel(II) complex (4-MeOC6H4)Ni(PCy3)2OTs proved to be a general catalyst for the Suzuki-Miyaura cross-coupling reactions of aryl sulfonates with arylboronic acids. By limiting the amount of the water in the initial catalytically active Ni(0) species generation stage, Ni(PCy 3)2X2 (X=Cl, Br) could also be efficient catalysts for the cross-coupling reactions a variety of aryl/activated alkenyl tosylates with arylboronic acids. The mild reaction condition, the easy availability of the catalysts and excellent coupling yields make these catalyst systems potentially useful in organic synthesis. Copyright
- Xing, Chun-Hui,Lee, Jeng-Ru,Tang, Zhen-Yu,Zheng, Jin Rong,Hu, Qiao-Sheng
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supporting information; experimental part
p. 2051 - 2059
(2011/10/12)
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- Suzuki-Miyaura cross-coupling of aryl carbamates and sulfamates: Experimental and computational studies
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The first Suzuki-Miyaura cross-coupling reactions of the synthetically versatile aryl O-carbamate and O-sulfamate groups are described. The transformations utilize the inexpensive, bench-stable catalyst NiCl 2(PCy3)2 to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups are tolerated, in addition to those that possess ortho substituents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative addition with carbamates or sulfamates occurs via a five-centered transition state, resulting in the exclusive cleavage of the aryl C-O bond. Water is found to stabilize the Ni-carbamate catalyst resting state, which thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest.
- Quasdorf, Kyle W.,Antoft-Finch, Aurora,Liu, Peng,Silberstein, Amanda L.,Komaromi, Anna,Blackburn, Tom,Ramgren, Stephen D.,Houk,Snieckus, Victor,Garg, Neil K.
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scheme or table
p. 6352 - 6363
(2011/06/19)
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- CROSS-COUPLING OF PHENOLIC DERIVATIVES
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Embodiments of the invention provide methods and materials for chemical cross-coupling reactions that utilize unconventional phenol derivatives as cross-coupling partners. Embodiments of the invention can be used to synthesize a variety of useful organic compounds, for example the anti-inflammatory drug flurbiprofen.
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Page/Page column 9; sheet 13/14
(2011/04/19)
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