- Preparation of ammonium cerium phosphate via low-heating solid state reaction and its catalysis for benzyl acetate synthesis
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Ammonium cerium phosphate was prepared with (NH4)3PO4?3H2O and Ce(SO4)2?4H2O as raw materials and PEG-400 as surfactant via a solid state reaction at low-heating temperature. The characterization result of XRD indicates that the molecular formula of the product was (NH4)2Ce(PO4)2?H2O. The synthesis of benzyl acetate was carried out with H2SO4/ammonium cerium phosphate as catalyst, and uniform experimental design as well as data mining technology was applied to the experiments, in which the effect of the reaction time, the molar ratio of acid to alcohol and the amount of catalyst on the conversion yield of acetic acid were studied. When benzalcohol was 0.10 mol, under the optimal reaction conditions, i.e. reaction time of 174 min, 2.02 of molar ratio of acid to alcohol and 0.5 g of catalyst, the esterification rate of acetic acid was 97.9%. The ammonium cerium phosphate had potential for industry application since it not only was feasible and simple in synthesis technics, but also had good catalysis activity for the synthesis of benzyl acetate.
- Liao, Sen,Chen, Zhipeng,Liu, Gang,Tian, Xiaozhen,Wang, Tianshun,Wu, Wenwei
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- Organocatalysis by site-isolated N-heterocyclic carbenes doped into the UIO-67 framework
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Two imidazolium-tagged biphenyldicarboxylates were synthesized and incorporated into the UiO-67 framework. Post synthetic exchange did not prove a useful route to these materials. Alternatively, mixed-linker synthesis of the solid afforded materials loaded with 6-7% imidazolium linker, corresponding to fewer than one active site per cage. Powder X-ray diffraction patterns for the doped metal-organic frameworks (MOFs) revealed that they were isostructural with UiO-67. Once activated, the N-heterocylic carbene (NHC) containing MOF was found to catalyze the transesterification of vinyl acetate with benzyl alcohol in good yield. The catalyst could be recycled with a modest drop in conversion. This is the first report of a NHC-doped MOF acting as an organocatalyst.
- Schumacher, William T.,Mathews, Madeleine J.,Larson, Sean A.,Lemmon, Carl E.,Campbell, Karin A.,Crabb, Brendan T.,Chicoine, Brent J.-A.,Beauvais, Laurance G.,Perry, Marc C.
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- Asymmetric syntheses of 8-oxabicyclo[3,2,1]octane and 11-oxatricyclo[5.3.1.0]undecane from glycals
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Herein, we describe an efficient method to prepare enantiomerically pure 8-oxabicyclo[3.2.1]octanes via gold(i)-catalyzed tandem 1,3-acyloxy migration/Ferrier rearrangement of glycal derived 1,6-enyne bearing propargylic carboxylates. The resultant compou
- Liao, Hongze,Leng, Wei-Lin,Le Mai Hoang, Kim,Yao, Hui,He, Jingxi,Voo, Amanda Ying Hui,Liu, Xue-Wei
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- Finding the Switch: Turning a baeyer-villiger monooxygenase into a NADPH Oxidase
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By a targeted enzyme engineering approach, we were able to create an efficient NADPH oxidase from a monooxygenase. Intriguingly, replacement of only one specific single amino acid was sufficient for such a monooxygenase-to-oxidase switch - a complete transition in enzyme activity. Pre-steady-state kinetic analysis and elucidation of the crystal structure of the C65D PAMO mutant revealed that the mutation introduces small changes near the flavin cofactor, resulting in a rapid decay of the peroxyflavin intermediate. The engineered biocatalyst was shown to be a thermostable, solvent tolerant, and effective cofactor-regenerating biocatalyst. Therefore, it represents a valuable new biocatalytic tool.
- Brondani, Patrcia B.,Dudek, Hanna M.,Martinoli, Christian,Mattevi, Andrea,Fraaije, Marco W.
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- Inline Reaction Monitoring of Amine-Catalyzed Acetylation of Benzyl Alcohol Using a Microfluidic Stripline Nuclear Magnetic Resonance Setup
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We present an in-depth study of the acetylation of benzyl alcohol in the presence of N,N-diisopropylethylamine (DIPEA) by nuclear magnetic resonance (NMR) monitoring of the reaction from 1.5 s to several minutes. We have adapted the NMR setup to be compatible to microreactor technology, scaling down the typical sample volume of commercial NMR probes (500 μL) to a microfluidic stripline setup with 150 nL detection volume. Inline spectra are obtained to monitor the kinetics and unravel the reaction mechanism of this industrially relevant reaction. The experiments are combined with conventional 2D NMR measurements to identify the reaction products. In addition, we replace DIPEA with triethylamine and pyridine to validate the reaction mechanism for different amine catalysts. In all three acetylation reactions, we find that the acetyl ammonium ion is a key intermediate. The formation of ketene is observed during the first minutes of the reaction when tertiary amines were present. The pyridine-catalyzed reaction proceeds via a different mechanism.
- Oosthoek-De Vries, Anna Jo,Nieuwland, Pieter J.,Bart, Jacob,Koch, Kaspar,Janssen, Johannes W. G.,Van Bentum, P. Jan M.,Rutjes, Floris P. J. T.,Gardeniers, Han J. G. E.,Kentgens, Arno P. M.
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- Electrochemical reduction of methyl 2-bromomethylbenzoate at carbon cathodes in dimethylformamide containingwater
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Cyclic voltammetry and controlled-potential electrolysis have been employed to examine the electrochemical reduction of methyl 2-bromomethylbenzoate at carbon cathodes in dimethylformamide (DMF) containing tetramethylammonium tetrafluoroborate (TMABF4). A cyclic voltammogram for the reduction of the substrate exhibits one irreversible cathodic wave with a peak potential of -1.45 V vs. SCE, which is due to the two-electron cleavage of the benzylic carbon-bromine bond. The corresponding reductive peak current also increases incrementally with the amount of water in DMF. Bulk electrolyses of methyl 2-bromomethylbenzoate have been carried out at -1.85 V vs. SCE with different concentrations of water in the solvent. The reduction process involves carbanion intermediates to afford various products including phthalide, which is generated via intramolecular cyclization that is affected by the presence of water. Detailed mechanism for the electrochemical reaction is proposed and further studied by isotope incorporation experiment.
- Allen, Caroline R.,Brown, Drew K.,Potts, Jessica L.,Ji, Chang
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- P-Cymenesulphonic acid: An organic acid synthesised from citrus waste
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An organic acid, p-cymene-2-sulphonic acid, is synthesised from citrus waste and demonstrated to be comparable to p-toluenesulphonic acid in examples of acid catalysis. Firstly the essential oil found in citrus waste is extracted by either steam distillation or microwave irradiation. Oxidising the limonene in the citrus oil to p-cymene followed by sulphonation gives p-cymene-2-sulphonic acid.
- Clark, James H.,Fitzpatrick, Emma M.,MacQuarrie, Duncan J.,Pfaltzgraff, Lucie A.,Sherwood, James
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- Synthesis of benzyl acetate catalyzed by lipase immobilized in nontoxic chitosan-polyphosphate beads
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Enzymes serve as biocatalysts for innumerable important reactions, however, their application has limitations, which can in many cases be overcome by using appropriate immobilization strategies. Here, a new support for immobilizing enzymes is proposed. This hybrid organic-inorganic support is composed of chitosan—a natural, nontoxic, biodegradable, and edible biopolymer—and sodium polyphosphate as the inorganic component. Lipase B from Candida antarctica (CALB) was immobilized on microspheres by encapsulation using these polymers. The characterization of the composites (by infrared spectroscopy, thermogravimetric analysis, and confocal Raman microscopy) confirmed the hybrid nature of the support, whose external part consisted of polyphosphate and core was composed of chitosan. The immobilized enzyme had the following advantages: possibility of enzyme reuse, easy biocatalyst recovery, increased resistance to variations in temperature (activity declined from 60?C and the enzyme was inactivated at 80 ?C), and increased catalytic activity in the transesterification reactions. The encapsulated enzymes were utilized as biocatalysts for transesterification reactions to produce the compound responsible for the aroma of jasmine.
- Melo, Ana D. Q.,Silva, Francisco F. M.,Dos Santos, José C. S.,Fernández-Lafuente, Roberto,Lemos, Telma L. G.,Dias Filho, Francisco A.
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- Ultrasound assisted heteropoly acid catalyst SiW12/SiO 2 for synthesis of benzyl acetate
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Under ultrasonic radiation, benzyl acetate is synthesized from benzyl alcohol and glacial acetic acid in presence of catalyst SiW12/ SiO2. The catalyst was prepared and characterized by IR, X-ray diffraction and SEM in the experiment. The XRD result indicates that heteropoly acid retains the Keggin-type structure. The kinetic parameters of reaction were, respectively measured at 90, 100 and 110 °C and the kinetic equation was built. Then, the effects of reaction temperature, the amount of catalyst, molar ratio of benzyl alcohol to glacial acetic acid and ultrasonic intensity on the esterification yield were discussed. The results showed that the optimum operating parameters for the present work when 10 kHz ultrasonic frequency and 1.0 W/cm2 ultrasonic intensity are as follows: reaction temperature: 110 °C, use amount of catalyst: 1.5 g, molar ratio of benzyl alcohol to glacial acetic acid: 1.5; reaction time: 75 min. Under such conditions, the esterification yield of the reaction reached above 95.3 %.
- Chen, Xi,Wang, Jun,Han, Yue,Lu, Xiao-Ping,Han, Ping-Fang
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- The Darbeau-White-Gibble reaction: An N-nitrosoamide-mediated Ritter-type reaction. Part I. A study of electronic, steric, and orbital effects in the nucleophile1a
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Benzyl cations were generated via thermal decomposition of N-benzyl-N-nitrosopivalamide in molten 4-R-substituted benzonitriles (R = NH2, Me2N, MeO, Me, H, F, and CF3). In each case, the benzyl cation was intercepted competitively by pivalate ion to yield benzyl pivalate and by the benzonitriles to yield the corresponding N-4-R-benzonitrilium ion. The latter onium ions reacted with pivalate ion to form benzimidic anhydrides which rearranged to yield N-4-R-benzoyl-N-pivaloylbenzylamines (i.e. unsymmetrical diacylamines). The yield of diacylamines (maximum ~10.6% for R = H) is smaller than from the corresponding reactions in acetonitrile and varied systematically with the nature and location of the R group on the aromatic nucleus. Both electron-releasing and electron-withdrawing groups at the para position effected a diminution of the yield of diacylamine; indeed for R = NH2, no diacylamine was formed. ortho Substitution of the aromatic nucleus resulted in significantly diminished yields of diacylamine, as did nucleophilic attack on the nitrilium ion by pivalate rather than acetate. Thus, both electronic and steric effects in nucleophilic attack on the nitrilium carbon were observed. The ratios of counterion-derived product to solvent-derived product for both the first-formed benzyl cation and the less reactive benzonitrilium ion are similar. This observation is interpreted in terms of the intermediacy of nitrogenous entity-separated ion-pairs in these deaminations.
- Darbeau,Gibble,Pease,Bridges,Siso,Heurtin
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- Converting phenylacetone monooxygenase into phenylcyclohexanone monooxygenase by rational design: Towards practical Baeyer-Villiger monooxygenases
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A homology model of the most frequently used, but thermally somewhat labile, Baeyer-Villiger monooxygenase, cyclohexanone monooxygenase (CHMO) has been derived on the basis of the recently published crystal structure of the thermally stable phenylacetone monooxygenase (PAMO). This has led to the identification of a structural element crucial for substrate acceptance and stereoselectivity, namely an arginine-interacting loop near the active site. A bulge in this loop occurring in PAMO (but not in CHMO) has been eliminated by mutation, enhancing the range of substrate acceptance and enantioselectivity of Baeyer-Villiger reactions while maintaining high thermal stability.
- Bocola, Marco,Schulz, Frank,Leca, Francois,Vogel, Andreas,Fraaije, Marco W.,Reetz, Manfred T.
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- Poly(ionic liquid)s based on imidazolium hydrogen carbonate monomer units as recyclable polymer-supported N-heterocyclic carbenes: Use in organocatalysis
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Synthesis of novel poly(ionic liquid)s, namely, poly(1-vinyl-3- alkylimidazolium hydrogen carbonate)s, denoted as poly([NHC(H)][HCO 3])s or PVRImHCO3, where R is an alkyl group (R = ethyl, butyl, phenylethyl, dodecyl), is described. Two distinct synthetic routes were explored. The first method is based on the free-radical polymerization (FRP) of 1-vinyl-3-alkylimidazolium monomers featuring a hydrogen carbonate counter anion (HCO3-), denoted as VRImHCO3. The latter monomers were readily synthesized by alkylation of 1-vinylimidazole (VIm), followed by direct anion exchange of 1-vinyl-3-alkylimidazolium bromide monomers (VRImBr), using potassium hydrogen carbonate (KHCO3) in methanol at room temperature. Alternatively, the same anion exchange method could be applied onto FRP-derived poly(1-vinyl-3-alkylimidazolium bromide) precursors (PVRImBr). All PVRImHCO3 salts proved air stable and could be manipulated without any particular precautions. They could serve as polymer-supported precatalysts to generate polymer-supported N-heterocyclic carbenes, referred to as poly(NHC)s, formally by a loss of "H2CO3" (H2O +CO2) in solution. This was demonstrated through selected organocatalyzed reactions of molecular chemistry, known as being efficiently mediated by molecular NHC catalysts, including benzoin condensation, transesterification and cyanosilylation of aldehyde. Of particular interest, recycling of the polymer-supported precatalysts was possible by re-carboxylation of in situ generated poly(NHC)s. Organocatalyzed reactions could be performed with excellent yields, even after five catalytic cycles.
- Coupillaud, Paul,Pinaud, Julien,Guidolin, Nicolas,Vignolle, Joan,Fevre, Mareva,Veaudecrenne, Ellen,Mecerreyes, David,Taton, Daniel
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- Free-Radical Aromatic Nitromethylation Promoted by Cerium(IV)
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A search for metal salt oxidants, other than manganese(III) acetate, capable of effecting aromatic nitromethylation with nitromethane was undertaken.Of the many screened, cerium(IV) salts showed the most promise.Cerium(IV) ammonium nitrate gave high, though initially erratic, yields (essentially 100percent yield of isomeric α-nitroxylenes from toluene and α-nitrotoluene from benzene).However, nitration products and aromatic aldehydes were generated as well.Product formation was followed as a function of time in these reactions, and nitromethylation products were shown to be converted to the corresponding isomeric tolualdehydes or benzaldehyde upon prolonged heating.Cerium(III) nitrate was shown to be primarily responsible for promoting this side reaction.Cerium(IV) acetate, generated in solution by ozonolysis of either cerium(III) nitrate or a mixture of cerium(III) acetate and cerium(III) nitrate in acetic acid, also was shown to promote high yields of nitromethylation products.Furthermore, this reaction was free of side products.Isomer studies and relative rates for nitromethylation were determined for both cerium(IV) salts in comparison with manganese(III) acetate.A Hammett treatment in each case gave similar ρ values (vs. ?+): -2.3 from manganese(III) acetate, -2.0 from cerium(IV) ammonium nitrate, and -1.9 from cerium(IV) acetate, indicating a common intermediate in each case.The nitromethyl radical, believed to the substituting entity, exhibits marked electrophilic properties.
- Kurz, Michael E.,Ngoviwatchai, Preecha
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- ACETYLATION BY KETENE OF ALCOHOLS SUPPORTED ON SOLID ADSORBENTS
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Primary, secondary, and tertiary alcohols supported on solid adsorbents such as alumina, silica gel, celite, magnesium oxide, zinc oxide, titanium oxide, and charcoal were acetylated by ketene in good yields.
- Chihara, Teiji,Takagi, Yuzuru,Teratani, Shousuke,Ogawa, Haruo
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- The tribromolanthanoids (LnBr3) catalysed reactions of benzyl alkyl ethers and carboxylic acids promoted by microwave irradiation
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The reaction between benzyl ethers and carboxylic acids was catalyzed efficiently by LnBr3 (Ln = La, Nd, Sm, Dy, Er), due to its weak Lewis acidity, with microwave irradiation to afford esters.
- Yulin,Yuncheng
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- Synthesis and applications of quaternized highly branched polyacrylamide as a novel multi-site polymeric phase transfer catalyst
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In current study, quaternized highly branched polyacrylamide (HBAA) was synthesized and used as an efficient multi-site polymeric phase transfer catalyst in nucleophilic substitution reactions and also in synthesis of α, β-unsaturated nitriles from reaction of acetonitrile and carbonyl compounds. The quaternized HBAA was synthesized via two steps. First, HBAA was synthesized via self-condensing vinyl polymerization of acrylamide at appropriate molar ratio of monomer to diperiodatocuprate(III). In the second step, 3-acrylamidopropyl trimethylammonium iodide was polymerized on peripheral area of the HBAA in the presence of diperiodatocuprate(III) solution again. The thermal behavior of HBAA and that of the quaternized HBAA were studied by DSC and TGA analysis. This phase transfer catalyst was easily recovered after reaction and reused several times without any loss of activity.
- Mahdavi, Hossein,Amirsadeghi, Mehdi
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- REDUCTION OF α-HALOCARBONYL COMPOUNDS WITH SODIUM HYDROGEN TELLURIDE
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Sodium hydrogen telluride is an efficient reagent for dehalogenation os α-halocarbonyl compounds
- Osuka, Atsuhiro,Suzuki, Hitomi
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- Glycerol-glycerol triacetate mixtures as green reaction mediums
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Three representative organic reactions were performed in various glycerol-triacetin mixtures to tune the polarity of the reaction mixture and thus to increase both the solubility of reactants and the product yields. In all reactions, it was found that reaction performance was affected by the glycerol to triacetin ratio as the solubility of the substrates in the solvent determined product yield. Thereby, employing optimal glycerol to triacetin ratio will result in maximum product yield.
- Wolfson,Dlugy,Mordechaiev,Sliman,Tavor
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- Encapsulated N-heterocyclic carbenes in silicones without reactivity modification
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(Chemical Equation Presented) Let them off the leash! Silicone protecting media allow the manipulation and storage of air- and moisture-sensitive N-heterocyclic carbenes (NHCs). Calculations show that a weak carbene-Lewis acid interaction minimizes decomposition of NHCs but does not inhibit NHC reactivity.
- Bonnette, Fabien,Kato, Tsuyoshi,Destarac, Mathias,Mignani, Gerard,Cossio, Fernando P.,Baceiredo, Antoine
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- Piperylene sulfone: A labile and recyclable DMSO substitute
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The properties and uses of piperylene sulfone as a new, recyclable dipolar, aprotic solvent for conducting organic reactions are presented. The Royal Society of Chemistry.
- Vinci,Donaldson,Hallett,John,Pollet,Thomas,Grilly,Jessop,Liotta,Eckert
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- Catalytic Cascade Access to Biaryl-2-Methyl Acetates from Pyruvate O-Arylmethyl Ketoximes via the Palladium-Catalyzed C(sp2)H Bond Arylation and C?O Bond Solvolysis
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A catalytic cascade has been developed for the synthesis of biaryl-2-methyl acetates via a palladium-catalyzed ortho-C(sp2)?H bond arylation of pyruvate O-arylmethyl ketoximes with aryl iodides followed by a solvolysis, in which the pyruvic ketoxime ester as a new auxiliary is employed to direct the C(sp2)?H bond activation. The straightforward treatment of O-arylmethyl hydroxylamines and ethyl pyruvate with aryl iodides also provides the target products in a one-pot fashion. Furthermore, the new palladacycle intermediate is unambiguously confirmed by single-crystal X-ray diffraction analysis. A plausible reaction pathway is proposed for the Pd-catalyzed arylation-acetolysis sequence. (Figure presented.).
- Shao, Ling-Yan,Xing, Li-Hao,Guo, Ying,Yu, Kun-Kun,Wang, Wei,Liu, Hong-Wei,Liao, Dao-Hua,Ji, Ya-Fei
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- Key properties promoting high activity and stability of supported PdSb/TiO2 catalysts in the acetoxylation of toluene to benzyl acetate
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The influence of thermal pretreatment in air, helium and 10% H 2/He on the catalytic performance of a supported 9% Pd, 12% Sb/TiO2 catalyst in the gas phase acetoxylation of toluene has been studied by integrated evaluation of catalytic tests and catalyst characterization using mainly XRD, TEM and XPS. A pretreatment temperature of 600 °C is beneficial for shortening the activation period, while the atmosphere during thermal pretreatment influences the long-term stability. Highest catalytic performance with a good long-term stability was reached with pretreatment in He, which creates Sb-containing Pd particles, on which a mixed Pd0/PdO surface is formed during time on stream. Sb stabilizes oxidized Pd species and leads to more stable catalysts in contrast to air-calcined samples. The catalyst pretreated in H2/He was completely inactive, due to the formation of a stable Pd8Sb3 alloy.
- Gatla,Madaan,Radnik,Kalevaru,Pohl,Lücke,Martin,Brückner
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- Expanding the biocatalytic toolbox of flavoprotein monooxygenases from Rhodococcus jostii RHA1
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With the aim to enlarge the set of available flavoprotein monooxygenases, we have cloned 8 unexplored genes from Rhodococcus jostii RHA1 that were predicted to encode class B flavoprotein monooxygenases. Each monooxygenase can be expressed as soluble protein and has been tested for conversion of sulfides and ketones. Not only enantioselective sulfoxidations, but also enantioselective Baeyer-Villiger oxidations could be performed with this set of monooxygenases. Interestingly, in contrast to known class B flavoprotein monooxygenases, all studied biocatalysts showed no nicotinamide coenzyme preference. This feature coincides with the fact that the respective sequences appear to form a discrete group of sequence related proteins, distinct from the known class B flavoprotein monooxygenases subclasses: the so-called flavin-containing monooxygenases (FMOs), N-hydroxylating monooxygenases (NMOs) and Type I Baeyer-Villiger monooxygenases (BVMOs). Taken together, these data reveal the existence of a new subclass of class B flavoprotein monooxygenases, which we coined as Type II FMOs, that can perform Baeyer-Villiger oxidations and accept both NADPH and NADH as coenzyme. The uncovered biocatalytic properties of the studied Type II FMOs make this newly recognized subclass of monooxygenases of potential interest for biocatalytic applications.
- Riebel, Anette,De Gonzalo, Gonzalo,Fraaije, Marco W.
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- The Impact of Reaction Pressure on the Catalytic Performance of the Pd-Sb/TiO2 Catalyst in the Acetoxylation of Toluene into Benzyl Acetate
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The acetoxylation of toluene in the presence of acetic acid and oxygen was performed over a Pd-Sb/TiO2 catalyst at 210°C and at various reaction pressures (1-10bar). A remarkable improvement in the catalytic performance and a significant shortening of the induction period were found with an increase in pressure. At a pressure of 6bar, the highest toluene conversion of 75% and 100% selectivity for benzyl acetate were observed. This result could be due to both the restructuring of the catalyst surface and to the formation of active Pd-Sb particles of desired size, composition, and shape during the course of the induction period. Samples of the most-active and spent catalysts were studied by ex situ and insitu XRD, XPS, and TEM.
- Madaan, Neetika,Gatla, Suresh,Kalevaru, Venkata Narayana,Radnik, Joerg,Pohl, Marga-Martina,Luecke, Bernhard,Brueckner, Angelika,Martin, Andreas
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- Hydrothermal synthesis of imidazole functionalized carbon spheres and their application in catalysis
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We describe the production and catalytic application of highly functionalized mesoporous carbonaceous materials, obtained via a one step green and cheap process relying on the hydrothermal carbonization of carbohydrates (e.g. glucose) in the presence of functional organic monomers (e.g. vinyl imidazole). The resulting materials could be further functionalized to feature imidazolium bromides on their surface and be used for various transesterification, Knoevenagel and Aldol reactions.
- Demir-Cakan, Rezan,Makowski, Philippe,Antonietti, Markus,Goettmann, Frederic,Titirici, Maria-Magdalena
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- CARBON SILICON BOND CLEAVAGE IN THE OXIDATION OF BENZYLIC SILANES BY CERIUM(IV) AMMONIUM NITRATE
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Benzyltrimethylsilanes react with cerium(IV) ammonium nitrate in AcOH to give products of C-Si cleavage (benzyl nitrate and acetate), under very mild conditions and in quantitative yields.The reaction rate is very sensitive to the nature of the ring substituents (ρ= -5.4), which clearly suggests the operation of one electron transfer mechanism.
- Baciocchi, Enrico,Del Giacco, Tiziana,Rol, Cesare,Sebastiani, Giovanni Vittorio
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- Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor
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Use of vinyl acetate as acyl donor in transesterification of benzyl alcohol catalyzed by a commercially available lipase (Lipozyme RM IM) gave 100% conversion in 10 min. The excess acyl donor and the enzyme could be recovered and reused. Unlike the chemical catalytic processes, it produced no undesirable side product.
- Majumder, Abir B.,Singh, Bhupender,Dutta, Debjit,Sadhukhan, Sushabhan,Gupta, Munishwar N.
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- Straightforward synthesis of N-protected benzylic amines by carbamoalkylation of aromatic compounds
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A wide range of alkoxycarbonyl protected benzylic amines have been synthesized in a three component reaction involving a carbamate an aldehyde and an aromatic substrate. This reaction proceeds through electrophilic substitution of the aromatic compound by a N-carbamoyl iminium which is generated in situ by condensation of the carbamate with the aldehyde.
- Bensel, Nicolas,Pevere, Virginie,Desmurs, Jean Roger,Wagner, Alain,Mioskowski, Charles
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- Poly(ionic liquid)-based monodisperse microgels as a unique platform for producing functional materials
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In this work, we report the microfluidic preparation of monodisperse imidazolium-based poly(ionic liquid) (PIL) microgels with a controlled size and morphology, and show that the imidazolium units in the microgel network can be exploited as reactive sites to efficiently access desired functional materials by a simple counteranion-exchange or conversion reaction. Moreover, based on the counteranion-exchange reaction, spatio-temporal engineering of the surface of the PIL microgels could also be realized, and a new and simple strategy for the fabrication of diverse anisotropic microgels (patchy particles) with great flexibility was developed. In addition, by exploiting the convenient generation of carbene units from the imidazolium moieties, as well as the carbonizable feature of PIL, the prepared PIL microgels could be further converted into stable carbene spheres and monodisperse carbon particles. All the results show that these monodisperse PIL-based microgels can serve as a very useful platform for facilely accessing various functional materials.
- Cui, Jiecheng,Gao, Ning,Li, Jian,Wang, Chen,Wang, Hui,Zhou, Meimei,Zhang, Meng,Li, Guangtao
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- New strategies for the synthesis of lactones using peroxymonosulphate salts, ionic liquids and microwave or ultrasound irradiation
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A new method for the rapid synthesis of lactones via the one-pot oxidation of alcohols with potassium peroxymonosulphate in an ionic liquid was developed. The use of microwave or ultrasonic irradiation increased the reaction rates significantly. Additionally, new peroxymonosulphate ionic liquids were synthesised and used as effective oxidants in the synthesis of lactones. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014.
- Matuszek, Karolina,Zawadzki, Przemyslaw,Czardybon, Wojciech,Chrobok, Anna
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- Tertiary Amine Oxides as Phase Transfer Catalysts for Substitution and Dichlorocyclopropanation Reactions
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Tertiary amine oxides catalyze a variety of phase transfer reactions, primarily by in situ deoxygenation to form the tertiary amine or derived catalyst.
- Garcia, Blanche J.,Leopold, Ahuva,Gokel, George W.
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- Catalytic activity comparison of Zr-SBA-15 immobilized by a Br?nsted-Lewis acidic ionic liquid in different esterifications
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Zirconium-incorporated SBA-15 mesoporous molecular sieves (Zr-SBA-15) with different Si/Zr molar ratios were one-pot synthesized and characterized by XRD, TEM and N2 physical adsorption. The Br?nsted-Lewis acidic ionic liquid 1-(3-sulfonic acid)-propy l-3-methylimidazole chlorozincinate ([mim-ps]Cl-ZnCl2) was prepared by a hydrothermal process and its acidity was measured by FT-IR spectroscopy using acetonitrile and pyridine as probes. The Zr-SBA-15 catalyst immobilized by [mim-ps]Cl-ZnCl2 (Zr-SBA-15/[mim-ps]Cl-ZnCl2) was prepared by a wet impregnation method and characterized by XRD, BET, FT-IR spectroscopy, TEM, XPS and TG. In particular, the catalytic activities of Zr-SBA-15 and Zr-SBA-15/[mim-ps]Cl-ZnCl2 in the esterification of acetic acid were evaluated with n-butyl alcohol (n-BuOH), benzyl alcohol (BnOH) and cyclohexanol (Naxol). The results show that Zr-SBA-15/[mim-ps]Cl-ZnCl2 exhibited enhanced catalytic properties compared to Zr-SBA-15. Under optimal conditions, the acetic acid conversion over Zr-SBA-15/[mim-ps]Cl-ZnCl2 reached 89.7, 93.6, and 84.9% for n-BuOH, BnOH and Naxol, respectively. After 5 cycles, the acetic acid conversion decreased slightly. Zr-SBA-15/[mim-ps]Cl-ZnCl2 was found to be an outstanding catalyst for esterification.
- Dai, Liming,Zhao, Qian,Fang, Minglan,Liu, Ruifeng,Dong, Mingfeng,Jiang, Tingshun
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- Poly(N-heterocyclic-carbene)s and their CO2 adducts as recyclable polymer-supported organocatalysts for benzoin condensation and transesterification reactions
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The synthesis of poly(N-heterocyclic carbene)s, denoted poly(NHC)s, and of their poly(NHC-CO2) adducts for a use in organocatalysis is described. Poly(NHC)s were readily obtained in a three-step sequence of reactions, involving i) the free-radical polymerization of ionic liquid monomers, that is, 1-vinyl-3-alkylimidazolium-type monomers with bromide (Br-) as counteranion, followed by ii) anion exchange of Br - for bis(trifluoromethanesulfonyl)imide (-NTf 2), of the poly(1-vinyl-3-alkylimidazolium bromide) precursors, affording poly(1-vinyl-3-alkylimidazolium bis(trifluoromethanesulfonyl)imide) derivatives, and iii) deprotonation of the latter polymeric ionic liquids with a strong base. Carbon dioxide (CO2) was found to reversibly react with poly(NHC)s forming relatively air-stable and thermolabile poly(NHC-CO 2) adducts. Both poly(NHC)s and their poly(NHC-CO2) adducts were used as polymer-supported organic catalysts and precatalysts, respectively, in transesterification and benzoin condensation reactions under homogeneous conditions. Both types of polymer-supported NHCs were recycled and used several times, but the manipulation of poly(NHC)s-like their molecular NHC analogues-was more complicated owing to their air and moisture sensitivity. In this regard, zwitterionic poly(NHC-CO2) adducts like their molecular NHC-CO2 analogues could be easier manipulated than their bare poly(NHC) counterparts, providing good to excellent yields even after several organocatalytic cycles, in particular toward the transesterification reaction.
- Pinaud, Julien,Vignolle, Joan,Gnanou, Yves,Taton, Daniel
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- Synthesis and characterization of Cp2Zr(C9H9O)2: A new zirconocene derivative catalyzed acetylation of 2-naphtol and benzyl alcohol
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The new zirconocene compound, Cp2Zr(C9H9O)2, was successfully prepared from the reaction of zirconocene dichloride with 1-indanol in 1:2 molar ratio in dry chloroform at the presence of triethylamine (Et3/
- Tarassoli, Abbas,Mohmedi-Kartalaee, Hadi
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- Magnetic nanoparticle-supported crown ethers
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Magnetic nanoparticle (MNP)-supported crown ethers were successfully prepared and evaluated as catalysts for solid-liquid phase-transfer reactions; the catalytic activities of the MNP-supported crown ethers were not inferior to those of non-supported crown ethers; after the reactions, the catalysts could be readily separated using an external magnet and reused without significant loss of catalytic efficiency. The Royal Society of Chemistry.
- Kawamura, Masato,Sato, Kazuhiko
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- Catalytic upgrading of carboxylic acids as bio-oil models over hierarchical ZSM-5 obtained: Via an organosilane approach
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Biomass is an interesting renewable energy resource as it is widespread in nature and low cost. The development of bio-oil derived from biomass as a fuel is still a scientific and industrial challenge. In this context, we demonstrate the synthetic method of bio-oil upgrading catalysts based on hierarchical zeolites and open up interesting perspectives for bio-oil upgrading processes. The hierarchical ZSM-5 zeolite has been successfully prepared via a direct hydrothermal synthesis with the aid of a commercial organosilane surfactant (TPOAC). The influences of TPOAC content and Si/Al ratio on hierarchical structures were also systematically studied. To illustrate their catalytic performances, an esterification reaction of various organic acids such as (acetic acid and levulinic acid) and alcohols was performed as the model reaction representing the bio-oil upgrading application. The synergic effect of acidity and the hierarchical structure of catalysts can greatly enhance the catalytic performance in terms of activity, product yield, coke formation, and reusability of the catalysts. For example, they can convert almost 100% of reactant in 8 h in the esterification of acetic acid and alcohols, whereas the conventional zeolite reveals significantly lower activity (20%). Interestingly, the hierarchical zeolite can also greatly improve the catalytic activity of the esterification of levulinic acid and ethanol to produce ethyl levulinate that can be used as a diesel miscible biofuel (DMB). In addition, the efficiency of hierarchical catalysts obtained by different synthesis methods is also discussed. This first example demonstrates that the hierarchical zeolite obtained via a direct synthesis approach can benefit bio-oil upgrading applications via the esterification of various carboxylic acids.
- Rodponthukwaji, Kamonlatth,Wattanakit, Chularat,Yutthalekha, Thittaya,Assavapanumat, Sunpet,Warakulwit, Chompunuch,Wannapakdee, Wannaruedee,Limtrakul, Jumras
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- One-step synthesis of benzyl acetate by gas phase acetoxylation of toluene over highly active and selective Pd-Sb-TiO2 catalysts
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Significantly high benzyl acetate selectivity of 85% at a toluene conversion of ca. 93% was achieved for the first time in a single step by gas phase acetoxylation over highly active and selective Pd-Sb-TiO2 catalysts.
- Benhmid,Narayana,Martin,Luecke
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- Esterification of Carboxylic Acids by Benzyl Chloride Using Quaternary Ammonium Salts
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The nucleophilicity of aliphatic carboxylic acids is enhanced in the presence of quaternary ammonium catalysts; benzyl chloride is esterified directly, e.g., by acetic acid in the absence of a base.
- Dakka, Jihad,Sasson, Yoel,Khawaled, Kamal,Bram, Georges,Loupy, Andre
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- Structural characterization and substrate specificity of VpAAT1 protein related to ester biosynthesis in mountain papaya fruit
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The aroma in fruits is an important attribute of quality that influences consumer's acceptance. This attribute is a complex character determined by a set of low molecular weight volatile compounds. In mountain papaya fruit (Vasconcellea pubescens) the aroma is determined mainly by esters, which are produced through an esterification reaction catalyzed by the enzyme alcohol acyltransferase (AAT) that utilizes alcohols and acyl-CoAs as substrates. In order to understand the molecular mechanism involved in the production of esters in this fruit, an AAT gene which has been previously cloned and characterized from mountain papaya (VpAAT1) was expressed in yeasts, and the highest enzyme activity of the recombinant protein was obtained when the enzyme was tested for its ability to produce benzyl acetate. On the other hand, to gain insight the mechanism of action at the molecular level, a structural model for VpAAT1 protein was built by comparative modelling methodology, which was validated and refined by molecular dynamics simulation. The VpAAT1 structure consists of two domains connected by a large crossover loop, with a solvent channel in the center of the structure formed between the two domains. Residues H166 and D170, important for catalytic action, displayed their side chains towards the central cavity of the channel allowing their interaction with the substrates. The conformational interaction between the protein and several ligands was explored by molecular docking simulations, and the predictions obtained were tested through kinetic analysis. Kinetic results showed that the lowest KM values were obtained for acetyl-CoA and benzyl alcohol. In addition, the most favorable predicted substrate orientation was observed for benzyl alcohol and acetyl CoA, showing a perfect coincidence between kinetic studies and molecular docking analysis.
- Morales-Quintana, Luis,Fuentes, Lida,Gaete-Eastman, Carlos,Herrera, Raúl,Moya-León, María Alejandra
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- Aqueous-level turnover frequency of lipase in organic solvent
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In this work, we explored the activation of a lipoprotein lipase from Burkholderia sp. by surfactants, sugars, and sugar-surfactant combinations for enhancing its activity in organic solvent. The lipase was most strongly activated by the combination of dextrin and anionic surfactant 1. As a result, its turnover frequency in anhydrous toluene reached 420 s-1, which was comparable to its aqueous counterpart. It was also found that a glucosamine-headed surfactant 8 as a molecular mimic of the dextrin-1 combination enhanced the turnover frequency of LPL to the aqueous level. As a rationale for such a high turnover frequency of lipoprotein lipase in anhydrous organic solvent, we speculate that the dextrin-1 couple or its mimic 8 could provide an efficient water-mimicking hydrogen bonding network around the enzyme in addition to the contribution as the oil surrogate, thus leading to a large increase of active enzyme molecules.
- Lee, Eungyeong,Oh, Yeonock,Choi, Yoon Kyung,Kim, Mahn-Joo
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- Noncross-linked polystyrene nanoencapsulation of ferric chloride: A novel and reusable heterogeneous macromolecular Lewis acid catalyst toward selective acetylation of alcohols, phenols, amines, and thiols
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Ferric chloride has been successfully nanoencapsulated for the first time on a non-cross-linked polystyrene matrix as the shell material via the coacervation technique. The resulting polystyrene nanoencapsulated ferric chloride was used as a novel and rec
- Alinejad, Sara,Donyapeyma, Ghazaleh,Rahmatpour, Ali
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- Dehydrogenative ester synthesis from enol ethers and water with a ruthenium complex catalyzing two reactions in synergy
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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.
- Ben-David, Yehoshoa,Diskin-Posner, Yael,Kar, Sayan,Luo, Jie,Milstein, David,Rauch, Michael
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supporting information
p. 1481 - 1487
(2022/03/07)
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- Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio-and Stereoselective Acylation of Alcohols
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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%.
- Koszelewski, Dominik,Brodzka, Anna,Madej, Arleta,Trzepizur, Damian,Ostaszewski, Ryszard
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p. 6331 - 6342
(2021/05/06)
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- ZWITTERIONIC CATALYSTS FOR (TRANS)ESTERIFICATION: APPLICATION IN FLUOROINDOLE-DERIVATIVES AND BIODIESEL SYNTHESIS
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An amide/iminium zwitterion catalyst has a catalyst pocket size that promotes transesterification and dehydrative esterification. The amide/iminium zwitterions are easily prepared by reacting aziridines with aminopyridines. The reaction can be applied a wide variety of esterification processes including the large-scale synthesis of biodiesel. The amide/iminium zwitterions allow the avoidance of strongly basic or acidic condition and avoidance of metal contamination in the products. Reactions are carried out at ambient or only modestly elevated temperatures. The amide/iminium zwitterion catalyst is easily recycled and reactions proceed in high to quantitative yields.
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Paragraph 0012; 0013; 0028
(2021/01/29)
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- An efficient, economical and eco-friendly acylation of alcohols and amines by alum doped nanopolyaniline under solvent free condition
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We report acylation of alcohols and amines employing acetic acid as an acylating agent in solvent free condition by using alum doped nanopolyaniline (NDPANI) as a catalyst. This environmentally benign method does not use corrosive acid anhydrides and acid chlorides for acylation and does not produce waste product. Also, a non-toxic potash alum was used for doping of polyaniline rather than corrosive acids. The reaction conditions represent an advance over established method not only in omitting the need for expensive catalysts or solvents but also in shortening the reaction time significantly. The advantages of this catalyst are non-hazardous, cheap, reusable, easy to prepare and handling.
- Behera, Satyaranjan,Patra, Braja N.
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- Fully recyclable Br?nsted acid catalyst systems
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Homogeneous and heterogeneous sulfonic acid catalysts are some of the most common catalysts used in organic chemistry. This work explores an alternative scheme using a fully recyclable polymeric solvent (a poly-α-olefin (PAO)) and soluble PAO-anchored polyisobutylene (PIB)-bound sulfonic acid catalysts. This PAO solvent is nonvolatile and helps to exclude water by its nonpolar nature which in turn drives reactions without the need for distillation of water, avoiding the need for excess reagents. This highly nonpolar solvent system uses polyisobutylene (PIB) bound sulfonic acid catalysts that are phase-anchored in solvents like PAO. The effectivenes of these catalysts was demonstrated by their use in esterifications, acetalizations, and multicomponent condensations. These catalysts and the PAO solvent phase show excellent recyclability in schemes where products are efficiently separated. For example, this non-volatile polymeric solvent and the PIB-bound catalyst can be recycled quantitatively when volatile products are separated and purified by distillation. In other cases, product purification can be effected by product self-separation or by extraction.
- Watson, Christopher B.,Kuechle, Adrianna,Bergbreiter, David E.
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p. 1266 - 1273
(2021/02/26)
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- Carboxylic Acid Reductase Can Catalyze Ester Synthesis in Aqueous Environments
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Most of the well-known enzymes catalyzing esterification require the minimization of water or activated substrates for activity. This work reports a new reaction catalyzed by carboxylic acid reductase (CAR), an enzyme known to transform a broad spectrum of carboxylic acids into aldehydes, with the use of ATP, Mg2+, and NADPH as co-substrates. When NADPH was replaced by a nucleophilic alcohol, CAR from Mycobacterium marinum can catalyze esterification under aqueous conditions at room temperature. Addition of imidazole, especially at pH 10.0, significantly enhanced ester production. In comparison to other esterification enzymes such as acyltransferase and lipase, CAR gave higher esterification yields in direct esterification under aqueous conditions. The scalability of CAR catalyzed esterification was demonstrated for the synthesis of cinoxate, an active ingredient in sunscreen. The CAR esterification offers a new method for green esterification under high water content conditions.
- Pongpamorn, Pornkanok,Kiattisewee, Cholpisit,Kittipanukul, Narongyot,Jaroensuk, Juthamas,Trisrivirat, Duangthip,Maenpuen, Somchart,Chaiyen, Pimchai
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supporting information
p. 5749 - 5753
(2021/02/01)
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- Encapsulation of heteropolyacids within hollow microporous polymer nanospheres for sustainable esterification reaction
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Herein, the Keggin structural phosphotungstic acid (HPW) has been successfully encapsulated within hollow microporous polymer nanospheres (H-MPNs) by a “ship-in-bottle” approach. The H-MPNs are formed by self-assembly induced by hyper-crosslinking of polylactide-b-polystyrene (PLA-b-PS). The obtained catalysts (HPW@H-MPNs) exhibit more sustainable availability than the previously reported HPW-supported catalysts in esterification reaction. This excellent sustainability can be attributed to the stable microporous channels in H-MPNs which are smaller than the molecular size of HPW, thereby effectively preventing the HPW from leaking out. Moreover, such catalysts also perform well in terms of catalytic activity and universality because of the combination of a hollow structure in the interior and permeable pore channels in the shells. This type of polymer carrier and general encapsulation method may provide a new strategy for developing more sustainable catalysts for various chemical reactions.
- He, Zhiwei,Huang, Kun,Song, Chunmei,Wang, Huaqing,Yu, Haitao,Zhang, Li
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- A pronounce approach on the catalytic performance of mesoporous natural silica toward esterification of acetic acid with iso-amyl, benzyl, and cinnamyl alcohols
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Catalytic esterification of acetic acid with iso-amyl, benzyl, and cinnamyl alcohols in the liquid phase over unmodified natural silica catalyst has been studied. The virgin and calcined catalysts were characterized by thermal analyses (Thermogravimetry (TG) and diffrential thermal analysis (DTA)), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and N2 sorption analyses. The acidity of natural silica catalysts was investigated using isopropyl alcohol dehydration and chemisorption of pyridine and dimethyl pyridine. The results indicated that most of the acidic sites are of Br?nsted type and of intermediate strength. The effect of different parameters such as reaction time, molar ratio, catalyst dosage, and calcination temperature was studied. Natural silica catalyst exhibited excellent catalytic performance with a selectivity of 100% to acetate esters formation. The maximum yields of isoamyl, benzyl, and cinnamyl acetate esters obtained in the batch conditions were 80, 81, and 83%, respectively. Whereas on adopting a simple distillation technique, these yields were successfully improved to higher values of 97, 98, and 90%, respectively. Experimental results manifested that the reaction followed Langmuir–Hinshelwood mechanism. Finally, the catalyst could be completely recycled without loss of its activity after four cycles of the esterification reactions.
- Abd El-Wahab, Mohamed M. M.,El-Gamal, Nadia O.,Goda, Mohamed N.,Said, Abd El-Aziz A.
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- Magnetically recyclable silica-coated ferrite magnetite-K10montmorillonite nanocatalyst and its applications in O, N, and S-acylation reaction under solvent-free conditions
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Novel silica-coated ferrite nanoparticles supported with montmorillonite (K10) have been prepared successfully by using a simple impregnation method. Further, these nanoparticles were characterized by using different analytical methods like FT-IR, PXRD, EDS, and FE-SEM techniques. In addition, these nanoparticles have been explored for their catalytic activity for the O, N, and S-acylation reactions under solvent-free conditions which gave moderate to excellent yields in a much shorter reaction time. Moreover, these nanoparticles could easily be separated out from the reaction medium after the reaction completion by using an external magnetic field and have been re-used for 10 cycles without any significant loss of the catalytic activity.
- Kumar, Pushpendra,Patil, Shripad M.,Tandon, Nitin,Tandon, Runjhun
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p. 21291 - 21300
(2021/07/01)
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- Discovery and Design of Family VIII Carboxylesterases as Highly Efficient Acyltransferases
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Promiscuous acyltransferase activity is the ability of certain hydrolases to preferentially catalyze acyl transfer over hydrolysis, even in bulk water. However, poor enantioselectivity, low transfer efficiency, significant product hydrolysis, and limited substrate scope represent considerable drawbacks for their application. By activity-based screening of several hydrolases, we identified the family VIII carboxylesterase, EstCE1, as an unprecedentedly efficient acyltransferase. EstCE1 catalyzes the irreversible amidation and carbamoylation of amines in water, which enabled the synthesis of the drug moclobemide from methyl 4-chlorobenzoate and 4-(2-aminoethyl)morpholine (ca. 20 % conversion). We solved the crystal structure of EstCE1 and detailed structure–function analysis revealed a three-amino acid motif important for promiscuous acyltransferase activity. Introducing this motif into an esterase without acetyltransferase activity transformed a “hydrolase” into an “acyltransferase”.
- Müller, Henrik,Godehard, Simon P.,Palm, Gottfried J.,Berndt, Leona,Badenhorst, Christoffel P. S.,Becker, Ann-Kristin,Lammers, Michael,Bornscheuer, Uwe T.
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supporting information
p. 2013 - 2017
(2020/11/30)
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- Trimethylsilyl Esters as Novel Dual-Purpose Protecting Reagents
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Trimethylsilyl esters, AcOTMS, BzOTMS, TCAOTMS, etc., are inexpensive and chemically stable reagents that pose a negligible environmental hazard. Such compounds prove to serve as efficient dualpurpose reagents to respectively achieve acylation and trimethylsilylation of alcohols under acidic or basic conditions. Herein, a detailed study on protection of various substrates and new methodological investigations is described.
- Chang, Ting-Shuo,Chen, Jyun-Siao,Hsieh, Ya-Chi,Hsu, Hsiao-Lin,Huang, Po-Hsun,Liu, Jen-Wei,Liu, Yu-Hao,Luo, Shun-Yuan,Wu, Hsin-Ru,Wu, Ren-Tsung,Zhang, Kai-Min
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supporting information
(2021/12/02)
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- Membrane transport inspired hydrolysis of non-activated esters at near physiological pH
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A positively charged micelle loaded with substrates was transported selectively to the reaction site (cathode) to promote the proximity and localization of the reactants (ester and hydroxide). The guided vehicular delivery coupled with electrolysis allows the hydrolysis of non-activated esters at near physiological pH with significant yields along with recyclability.
- Mandal, Raki,Mahanty, Kingshuk,Mandal, Subhendu,De Sarkar, Suman,Tarafdar, Pradip K.
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supporting information
p. 11088 - 11091
(2021/10/30)
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- Method for synthesizing benzyl acetate by using combined catalytic system
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The invention provides a method for synthesizing benzyl acetate by using a combined catalytic system, and belongs to the technical field of fine chemical engineering. According to the synthesis method, by taking dibenzyl ether as a raw material, selecting a combined catalyst comprising three components, namely a main catalyst, a leaving group and a trapping agent as a catalyst, the raw material reacts with acetic anhydride to obtain a crude product, and then rectification and purification are performed to obtain a benzyl acetate finished product. The main catalyst activates acetic anhydride and promotes formation of a reaction intermediate; the leaving group promotes the leaving of benzyl and inhibits the intramolecular rearrangement of benzyl; the trapping agent traps removed benzyl positive ions, helps elimination of benzyl, promotes the reaction to proceed to a main reaction route and inhibits generation of side reactions, the three components have a synergistic effect, the single-pass reaction yield of benzyl acetate can reach 88%-91%, the total yield can reach 93% or above, compared with the total yield of 80%-83% of an existing process, the yield of benzyl acetate is remarkably increased, and the production efficiency is improved.
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Paragraph 0057-0096
(2021/07/10)
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- Acyl Donor Intermediates in N-Heterocyclic Carbene Catalysis: Acyl Azolium or Azolium Enolate?
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Azolium enolates and acyl azolium cations have been proposed as intermediates in numerous N-heterocyclic carbene (NHC) catalyzed transformations. Acetyl azolium enolates were generated from the reaction of 2-propenyl acetate with both saturated (SIPr) and
- Biswas, Animesh,Neud?rfl, J?rg-M.,Schl?rer, Nils E.,Berkessel, Albrecht
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p. 4507 - 4511
(2021/02/03)
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- N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
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We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
- Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
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supporting information
p. 19631 - 19636
(2021/08/09)
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- Ring-contraction of hantzsch esters and their derivatives to pyrrolesviaelectrochemical extrusion of ethyl acetate out of aromatic rings
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Electrochemical ring-contraction of HEs and theirs pyridine derivatives is developed to obtain polysubstituted pyrroles. This process provides an orthogonal utilization of Hantzsch esters for the well-documented application as side chain or hydrogen donors. The formal transformation shows an extrusion of ethyl acetate out of the pyridine ring in a single step. In addition to the novel transformation, we also discovered the Lewis acid's intermolecular control of regioselectivity during an intramolecular electrochemical process. The reaction provides a number of polysubstituted pyrroles that have never been accessed, including pharmaceutical intermediates and photoswitches. An unusual 4-electron continuous reduction drives the unprecedented anionic dearomatization/ring-contraction/rearomatization pathway.
- Liu, Xu,Liu, Chang,Cheng, Xu
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supporting information
p. 3468 - 3473
(2021/05/21)
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- Spin glass behavior and oxidative catalytic property of Zn2MnO4 from a metathesis driven metastable precursor
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The reaction of chloride salts of zinc and manganese with NaOH yielded a cubic spinel structured metastable precursor at room temperature, driven mainly by the salt elimination process's energetics. While classical drying processes failed to produce the monophasic oxide, recrystallization under the hydrothermal conditions yielded Zn2MnO4 in nano dimensions. The sample consisted of crystallites with an average 6 nm size and had a lattice dimension of 8.396 (13) ?. The selected area electron diffraction pattern reiterated the occurrence of cubic inverse spinel. The presence of fingerprint (A1g and F2g) modes of an inverse spinel at 663 and 561 cm?1 in the Raman spectrum further supported our finding. The TEM-EDS analysis confirmed the ratio of Zn: Mn as 1.95:1. The sample showed an optical bandgap of 2.54 eV. X-ray photoelectron spectral analysis established the existence of manganese in the IV oxidation state. The presence of Mn (IV) with small amounts of Mn (III) (up to 20%) was confirmed from the electron paramagnetic spectra recorded at room temperature and 77 K. An average oxidation state of 3.85 was deduced from the chemical redox titration experiments. The pseudocapacitive behavior of the sample was evident in cyclic voltammetric experiments. The sample exhibited paramagnetic behavior at 298 K within the applied magnetic field of ±50 kOe. In the temperature-dependent measurements, the zero-field and field cooled data points of Zn2MnO4 diverged at 13 K, suggesting a spin-glass behavior. An effective magnetic moment of 4.31 BM was deduced for the sample. The inverse spinel effectively catalyzed the oxidation of phenol. It facilitated nearly 100% degradation of bisphenol-A to salicylaldehyde and phenylethyl alcohol (as major products) in the presence of H2O2 and at a pH of 9.
- Kushwaha, Shreya,Nagarajan, Rajamani
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- Genome mining reveals new bacterial type I Baeyer-Villiger monooxygenases with (bio)synthetic potential
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Baeyer-Villiger monooxygenases (BVMOs) are oxidorreductases that catalyze the oxidation of ketones in a very selective manner. By genome mining we detected seven putative type I BVMOs in Bradyrhizobium diazoefficiens USDA 110. As we established the phylogenetic relationships among them and with other type I BVMOs, we found out that they belong to different clades of the phylogenetic tree. Thus, we decided to clone and heterologously express five of them. Three of them, each one from a divergent phylogenetic group, were obtained as soluble proteins, allowing us to proceed with their biocatalytic assessment and enzymatic characterization. As to substrate scope and selectivity, we observed a complementary behavior among the three BVMOs. BVMO2 was the more versatile biocatalyst in whole-cell systems while BVMO4 and BVMO5 showed a narrow substrate profile with preference for linear ketones and particular regioselectivity for (±)-cis-bicyclo[3.2.0]hept-2-en-6-one.
- Bianchi, Dario A.,Carabajal, María Ayelén,Ceccoli, Romina D.,Rial, Daniela V.
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- Genome Mining of Oxidation Modules in trans-Acyltransferase Polyketide Synthases Reveals a Culturable Source for Lobatamides
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Bacterial trans-acyltransferase polyketide synthases (trans-AT PKSs) are multimodular megaenzymes that biosynthesize many bioactive natural products. They contain a remarkable range of domains and module types that introduce different substituents into growing polyketide chains. As one such modification, we recently reported Baeyer–Villiger-type oxygen insertion into nascent polyketide backbones, thereby generating malonyl thioester intermediates. In this work, genome mining focusing on architecturally diverse oxidation modules in trans-AT PKSs led us to the culturable plant symbiont Gynuella sunshinyii, which harbors two distinct modules in one orphan PKS. The PKS product was revealed to be lobatamide A, a potent cytotoxin previously only known from a marine tunicate. Biochemical studies show that one module generates glycolyl thioester intermediates, while the other is proposed to be involved in oxime formation. The data suggest varied roles of oxygenation modules in the biosynthesis of polyketide scaffolds and support the importance of trans-AT PKSs in the specialized metabolism of symbiotic bacteria.
- Ueoka, Reiko,Meoded, Roy A.,Gran-Scheuch, Alejandro,Bhushan, Agneya,Fraaije, Marco W.,Piel, J?rn
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supporting information
p. 7761 - 7765
(2020/03/25)
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- Chemoselective: O -formyl and O -acyl protection of alkanolamines, phenoxyethanols and alcohols catalyzed by nickel(ii) and copper(ii)-catalysts
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Achieving chemoselectivity is always crucial and challenging for bi-functional compounds, such as alkanolamines, that have both amines and alcohols as reactive functional groups. Achieving 100% selectivity for O-formyl and O-acyl protection of alkanolamines is one of the examples of such reactions. To avoid protection and deprotection steps and overcome this problem, a novel chemoselective, efficient, and simple protocol for functional group protection as O-formylation and O-acylation of alkanolamines and phenoxyethanols and competitive O-selectivity between alcohols and amines, catalyzed by Ni(ii) and Cu(ii) complexes with 8-hydroxyquinoline at a catalyst loading of only 5 mol% in a homogeneous medium has been presented here. Good to excellent yields are achieved in the absence of a solvent for O-formylation at room temperature with formic acid as the formyl source and O-acylation at 70 °C with acetic acid as the acyl source. In addition, minimal effluent and waste are generated during this reaction, as the corresponding sodium salts of acids could be recovered during the process and can be reused. This chemistry readily tolerates a variety of functional groups, as demonstrated by 20 examples with 100% chemoselectivity for O-formylation and O-acylation of alkanolamines and 30 examples of O-formylation and O-acylation of phenoxyethanols and alcohols in the presence of amines which have been synthesized successfully.
- Sonawane, Rahul B.,Sonawane, Swapnali R.,Rasal, Nishant K.,Jagtap, Sangeeta V.
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supporting information
p. 3186 - 3195
(2020/06/19)
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- Synthesis of Some Aromatic and Aliphatic Esters Using WO3/ZrO2 Solid Acid Catalyst under Solvent Free Conditions
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A simple method is delineated for the synthesis of substituted ester products in superior yields by esterification reaction under solvent unbound condition using tungsten upgraded ZrO2 solid acid catalyst at 353 K. The WO3/ZrO2 catalyst has been prepared by using impregnation method followed by calcination at 923 K over a period of 6 h in air atmosphere. SEM, XRD, FTIR, and BET surface area techniques were used to categorize this catalyst. Zirconia has both acidic and basic possessions which can be changed by incorporating suitable promoter atom like tungsten which in turn increases the surface area thereby enhancing the surface acidity. Impregnation of W6+ ions exhibits a strong influence on phase modification of zirconia from thermodynamically solid monoclinic to metastable tetragonal phase. Amalgamation of promoter W6+ will stabilize tetragonal phase which is active in catalyzing reactions. In esterification reaction WO3/ZrO2 catalyst was found to be stable, efficient and environmental friendly, effortlessly recovered by filtration, excellent yield of product and can be reusable efficiently.
- Guguloth, Vijaya Charan,Battu, Satyanarayana
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p. 2153 - 2157
(2020/09/16)
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- Alkyl substituted 4-N-oxazadisilinane cations: A new family of Si protic ionic liquids and its application on esterification reactions
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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.
- Alhaddad, Maha,Chakraborty, Priyanka,Hu, Jinsong,Huang, Kuo-Wei
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supporting information
(2020/06/08)
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- A rings-in-pores net: Crown ether-based covalent organic frameworks for phase-transfer catalysis
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We herein present a new family of crown ether-based covalent organic frameworks (CE-COFs) for the first time. The CE-COFs show excellent phase-transfer catalytic performance in various nucleophilic substitution reactions.
- Guo, Wen-Di,Hu, Bingwen,Jiang, Wei-Ling,Lou, Xiaobing,Ma, De-Li,Qi, Qiao-Yan,Shen, Ji-Chuang,Shen, Ming,Yang, Hai-Bo,Zhao, Xin
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supporting information
p. 595 - 598
(2020/01/29)
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- Sequence-Based Prediction of Promiscuous Acyltransferase Activity in Hydrolases
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Certain hydrolases preferentially catalyze acyl transfer over hydrolysis in an aqueous environment. However, the molecular and structural reasons for this phenomenon are still unclear. Herein, we provide evidence that acyltransferase activity in esterases highly correlates with the hydrophobicity of the substrate-binding pocket. A hydrophobicity scoring system developed in this work allows accurate prediction of promiscuous acyltransferase activity solely from the amino acid sequence of the cap domain. This concept was experimentally verified by systematic investigation of several homologous esterases, leading to the discovery of five novel promiscuous acyltransferases. We also developed a simple yet versatile colorimetric assay for rapid characterization of novel acyltransferases. This study demonstrates that promiscuous acyltransferase activity is not as rare as previously thought and provides access to a vast number of novel acyltransferases with diverse substrate specificity and potential applications.
- Badenhorst, Christoffel P. S.,Becker, Ann-Kristin,Berndt, Leona,Bornscheuer, Uwe T.,Godehard, Simon P.,Lammers, Michael,Müller, Henrik,Palm, Gottfried J.,Reisky, Lukas
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supporting information
p. 11607 - 11612
(2020/05/18)
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- Radical-Mediated Strategies for the Functionalization of Alkenes with Diazo Compounds
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One of the most common reactions of diazo compounds with alkenes is cyclopropanation, which occurs through metal carbene or free carbene intermediates. Alternative functionalization of alkenes with diazo compounds is limited, and a methodology for the addition of the elements of Z-CHR2 (with Z = H or heteroatom, and CHR2 originates from N2 CR2) across a carbon-carbon double bond has not been reported. Here we report a novel reaction of diazo compounds utilizing a radical-mediated addition strategy to achieve difunctionalization of diverse alkenes. Diazo compounds are transformed to carbon radicals with a photocatalyst or an iron catalyst through PCET processes. The carbon radical selectively adds to diverse alkenes, delivering new carbon radical species, and then forms products through hydroalkylation by thiol-assisted hydrogen atom transfer (HAT), or forms azidoalkylation products through an iron catalytic cycle. These two processes are highly complementary, proceed under mild reaction conditions, and show high functional group tolerance. Furthermore, both transformations are successfully performed on a gram-scale, and diverse γ-amino esters, γ-amino alcohols, and complex spirolactams are easily prepared with commercially available reagents. Mechanistic studies reveal the plausible pathways that link the two processes and explain the unique advantages of each.
- Su, Yong-Liang,Liu, Geng-Xin,Liu, Jun-Wen,Tram, Linh,Qiu, Huang,Doyle, Michael P.
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supporting information
p. 13846 - 13855
(2020/09/21)
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- Environmentally benign decarboxylative: N-, O-, and S-Acetylations and acylations
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An operationally simple and general method for acetylation and acylation of a wide variety of substrates (amines, alcohols, phenols, thiols, and hydrazones) has been reported. Meldrum's acid and its derivatives have been used as an air-stable, non-volatile, cost-effective, and easy to handle acetylating/acylating agent. Easily separable byproducts (CO2 and acetone) allowed the isolation of analytically pure acetylated products without the requirement of work-up and any chromatography. This journal is
- Ghosh, Santanu,Purkait, Anisha,Jana, Chandan K.
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supporting information
p. 8721 - 8727
(2020/12/30)
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- Amide/Iminium Zwitterionic Catalysts for (Trans)esterification: Application in Biodiesel Synthesis
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A class of zwitterionic organocatalysts based on an amide anion/iminium cation charge pair has been developed. The zwitterions are easily prepared by reacting aziridines with aminopyridines. They are catalytically applicable to transesterifications and dehydrative esterifications. Mechanistic studies reveal that the amide anion and iminium cation work synergistically in activating the reaction partners, with the iminium cationic moiety interacting with the carbonyl substrates through nonclassical hydrogen bonding. The reaction can be applied to large-scale synthesis of biodiesel under mild conditions.
- Lam, Ying-Pong,Ng, Wing-Hin,Tan, Fei,Tse, Ying-Lung Steve,Wang, Xinyan,Yeung, Ying-Yeung
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p. 8083 - 8092
(2019/08/26)
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- Enzyme-Catalyzed Synthesis of Esters in Water
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MsAcT catalyzes the esterification of primary alcohols in water. When utilizing acid and alcohol as starting materials low yields dictated by thermodynamics were observed. However, with activated esters such as ethyl acetate and vinyl acetate very high yields of the desired ester can be achieved in combination with the appropriate alcohol. This study investigated both the intrinsic kinetic properties of MsAcT for the hydrolysis and transesterification of esters in water as well as the thermodynamics of the reaction. In comparison to the chemical or enzymatic ester synthesis using either toxic reagent, and harsh organic solvents, the MsAcT-catalyzed synthesis of esters of primary alcohols can be achieved efficiently in water without neutralization steps.
- Mestrom, Luuk,Claessen, Jord G. R.,Hanefeld, Ulf
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p. 2004 - 2010
(2019/04/14)
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- Efficient Enzymatic Preparation of Flavor Esters in Water
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A straightforward biocatalytic method for the enzymatic preparation of different flavor esters starting from primary alcohols (e.g., isoamyl, n-hexyl, geranyl, cinnamyl, 2-phenethyl, and benzyl alcohols) and naturally available ethyl esters (e.g., formate, acetate, propionate, and butyrate) was developed. The biotransformations are catalyzed by an acyltransferase from Mycobacterium smegmatis (MsAcT) and proceeded with excellent yields (80-97%) and short reaction times (30-120 min), even when high substrate concentrations (up to 0.5 M) were used. This enzymatic strategy represents an efficient alternative to the application of lipases in organic solvents and a significant improvement compared with already known methods in terms of reduced use of organic solvents, paving the way to sustainable and efficient preparation of natural flavoring agents.
- Perdomo, Igor Chiarelli,Gianolio, Stefania,Pinto, Andrea,Romano, Diego,Contente, Martina Letizia,Paradisi, Francesca,Molinari, Francesco
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p. 6517 - 6522
(2019/06/20)
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- Hierarchically porous Br?nsted acidic ionic liquid functionalized nitrogen-doped carbons for pyrolysis biofuel upgrading via esterification of acetic acid with high boiling point alcohols
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Br?nsted acidic ionic liquid (BAIL) functionalized hierarchically porous nitrogen-doped carbons (NHPCs) with interesting 3D interconnected macro-meso-microporous structure are successfully prepared by chemical bonding ?[C3][SO3CF3?] (C3 = PrSO3H) groups throughout the NHPC supports that are obtained via a single step CaCO3 nanoparticle-directed nanocasting approach combined with K2C2O4 chemical activation and urea/melamine self-activation during the process of carbonization of glucose and urea/melamine. By changing initial urea-to-glucose weight ratio in the preparation systems, the macro/meso/micropore proportion of the resulting GU?[C3N][SO3CF3] catalysts are well-adjusted. The morphological characteristics, porosity properties and chemical structure of the prepared catalysts are well-characterized so that the contribution of the synergistic effect of CaCO3 nanoparticle and K2C2O4 to the formation of hierarchically porous structure is revealed. Owing to super strong Br?nsted acidity and unique hierarchically porous structure of the catalysts, they exhibit excellent heterogeneous acid catalytic activity in raw pyrolysis biofuel upgrading via esterification of acetic acid with high boiling point benzyl alcohol or 4-methoxybenzyl alcohol in toluene media, and therefore high acetic acid removal efficiency and efficient production of value-added benzyl acetate or 4-methoxybenzyl acetate are obtained simultaneously. The catalysts also show good reusability in target reactions, attributing to chemical interactions between BAILs and NHPC supports.
- Zhang, Qingqing,Zhang, Chaoyue,Sun, Yingnan,Guo, Yihang,Song, Daiyu
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- Application of Yttrium Iron Garnet as a Powerful and Recyclable Nanocatalyst for One-Pot Synthesis of Pyrano[2,3-c]pyrazole Derivatives under Solvent-Free Conditions
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The application of yttrium iron garnet (YIG) superparamagnetic nanoparticles as a new recyclable and highly efficient heterogeneous magnetic catalyst for one-pot synthesis of pyrano[2,3-c]pyrazole derivatives under solvent-free conditions, as well as etherification and esterification reactions are described. The advantages of the proposed method include the lack of organic solvents, clean reaction, rapid removal of the catalyst, short reaction times, excellent yields, and recyclability of the catalyst.
- Sedighinia,Badri,Kiasat
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p. 1755 - 1763
(2020/01/11)
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- Novel SO3H-functionalized polyoxometalate-based ionic liquids as highly efficient catalysts for esterification reaction
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Three novel heteropolyanion-based Br?nsted acidic ionic liquids (BAILs), butane mono sulfoacid-functionalized 1,10-phenanthrolinum, butane mono and bis sulfoacid-functionalized 1,4-dimethylpiperazinium salts of phosphortungstate catalyst (PhBs1-PW, [PipBs1]3-PW and [PipBs2]3-(PW)2) were synthesized and well characterized with FTIR, 1H and 13C NMR, Electro-Spray Ionization Mass Spectrometry (ESI-MS), Elemental analysis (CHNS), EDX and TG analysis techniques. The esterification reactions of monocarboxylic acids with monohydric alcohols were carried out using these catalysts. The introduced catalysts present a self-separation performance after reaction, which can be easily recovered and quite steadily reused as confirmed by six-run recycling test. Moreover, bis sulfoacid-functionalized 1,4-dimethylpiperazinium salt of phosphortungstate showed the best catalytic performance among the prepared catalysts for the esterification reaction.
- Keshavarz, Mosadegh,Iravani, Nasir,Parhami, Abolfath
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p. 272 - 278
(2019/04/25)
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- Cycloaddition of CO2 with epoxides and esterification reactions using the porous redox catalyst Co-POM@MIL-101(Cr)
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The catalytic activity of the recently reported Co-POM@MIL-101(Cr) composite, synthesized from K5[CoW12O40] (Co-POM) and chromium(iii) terephthalate (MIL-101), was studied in the solvent-free cycloaddition of CO2 with epoxides and esterification of acetic acid with various alcohols. The materials containing varying amounts of Co-POM were synthesized using a one-pot HF-free method in a "bottle around ship" strategy. The material was thoroughly characterized using several methods such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance spectroscopy (EPR). Temperature programmed desorption (TPD) of NH3 and CO2, and the CO2 adsorption capacity (adsorption isotherms) were used to study the acid-base properties of the materials. The combination of the electron-transfer character of Co(iii)-POM and ordered mesopores in MIL-101(Cr) creates an efficient catalytic system with mild conditions (90 °C and 20 bar CO2 pressure) for solvent-free cycloaddition of CO2 to various epoxides. Esterification of acetic acid with alcohols was also carried out using the Co-POM@MIL-101 catalysts and high yields were achieved for different alcohols. The catalysis experiments also clearly show that the active site in this heterogeneous catalyst is the Co(iii) center in the Keggin anion structure. It presumably conducts both the cycloaddition of CO2 to epoxides and the esterification reaction via an outer-sphere electron transfer mechanism using the Co(iii)/Co(ii) redox pair. The heterogeneous Co-POM@MIL-101 catalysts were separated by simple filtration and reused five times in the cycloaddition of CO2 with styrene epoxide and seven times for the esterification of acetic acid with benzyl alcohol with negligible leaching of Co-POM and no considerable loss of activity.
- Marandi, Afsaneh,Bahadori, Mehrnaz,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Frohnhoven, Robert,Mathur, Sanjay,Sandleben, Aaron,Klein, Axel
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supporting information
p. 15585 - 15595
(2019/10/19)
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- Fe3O4@PEG core/shell nanoparticles as magnetic nanocatalyst for acetylation of amines and alcohols using ultrasound irradiations under solvent-free conditions
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Abstract: Ultrasound irradiation was used to prepare one-pot Fe3O4@PEG core/shell nanostructure for the first time. The morphology, structure, and physicochemical properties were specified by different analytical techniques including field emission scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray powder diffraction, and vibrating sample magnetometer. For acetylation of phenols, alcohols, and amines, the synthesized Fe3O4@PEG core/shell nanoparticles were used as an efficient heterogeneous and green catalyst with acetic anhydride under sonication applying mild reaction conditions. Different electron-withdrawing and electron-donating substrates indicate a prominent yield of desired products with the merit of reusability of Fe3O4@PEG nanocatalyst and magnetic separation. Graphical Abstract: [Figure not available: see fulltext.].
- Veisi, Hojat,Nikseresht, Ahmad,Rostami, Afsaneh,Hemmati, Saba
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p. 507 - 520
(2018/10/24)
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- Manganese-mediated acetylation of alcohols, phenols, thiols, and amines utilizing acetic anhydride
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Manganese(II) chloride-catalyzed acetylation of alcohols, phenols thiols and amines with acetic anhydride is reported. This method is environment-friendly and economically viable as it involves inexpensive, relatively benign catalyst, mild reaction condition, and simple workup. Acetylation is performed under the solvent-free condition at ambient temperature and acetylated products obtained in good to excellent yields. Primary, secondary heterocyclic amines, and phenols with various functional groups are smoothly acetylated in good yields. This method exhibits exquisite chemoselectivity, the amino group is preferentially acetylated in the presence of a hydroxyl/thiol group.
- Jain, Isha,Sharma, Ramandeep,Malik, Payal
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supporting information
p. 2952 - 2960
(2019/09/13)
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- Acylation of Phenols, Alcohols, Thiols, Amines and Aldehydes Using Sulfonic Acid Functionalized Hyper-Cross-Linked Poly(2-naphthol) as a Solid Acid Catalyst
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Abstract: The hyper-cross-linked porous poly(2-naphthol) fabricated by the Friedel–Crafts alkylation of 2-naphthol has been functionalized with sulfonic acid to obtain a solid acid catalyst. The catalyst is applied for the protection of phenol, alcohols, thiols, amines and aldehydes with acetic anhydride at room temperature. The catalytic protection using the new solid acid is featured by achieving high yield at neat condition, needing no aqueous work-up and/or chromatographic separation, and showing excellent recycling efficiency, suggesting the potential of this sulfonated porous polymers as a new protection protocol in a wide range of sustainable chemical reactions. Graphical Abstract: [Figure not available: see fulltext.].
- Kalla, Reddi Mohan Naidu,Reddy, Sirigireddy Sudharsan,Kim, Il
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p. 2696 - 2705
(2019/05/28)
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- 4-Imidazol-1-yl-butane-1-sulfonic acid ionic liquid: Synthesis, structural analysis, physical properties and catalytic application as dual solvent-catalyst
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4-Imidazol-1-yl-butane-1-sulfonic acid (ImBu-SO3H) has been successfully synthetized and fully characterized by FT-IR and high-resolution NMR spectroscopy (1H, 13C). The “plausible” alternative structures of ImBu-SO3H were discussed on the basis of its NMR data. The ionic liquid showed interesting dual solvent-catalyst property, which was studied experimentally for the acetylation of a variety of functionalized alcohols, phenols, thiols, amines and α-tocopherol (α-CTP) as the most active form of vitamin E with acetic anhydride and which provided good yields within a short reaction time. ImBu-SO3H was successfully recycled by product extraction with an average recovered yield of 82% for 5 subsequent runs. The catalytic activity of the recycled ImBu-SO3H showed almost no loss even after five consecutive runs.
- Khaligh, Nader Ghaffari,Mihankhah, Taraneh,Johan, Mohd Rafie,Juan, Joon Ching
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p. 866 - 878
(2019/07/12)
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- An isolable iron(ii) bis(supersilyl) complex as an effective catalyst for reduction reactions
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An isolable 14-electron iron bis(supersilyl) complex, Fe[Si(SiMe3)3]2(THF)2, was successfully synthesized from the reaction of FeBr2 with K[Si(SiMe3)3] and its structure was unambiguously determined by single-crystal X-ray diffraction analysis. The complex is coordinatively unsaturated and exhibits high catalytic activity toward the hydrosilylation of carbonyl compounds and the reductive silylation of dinitrogen.
- Arata, Shogo,Sunada, Yusuke
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p. 2891 - 2895
(2019/03/06)
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- Benzoate Surfactants for Enhancing the Activity of Lipoprotein Lipase from Burkholderia Species in Organic Solvent
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Two benzoate surfactants were synthesized and examined as the additives for enhancing the activity of a lipoprotein lipase from Burkholderia species (BSLPL) in organic solvent. It was found that the benzoate surfactants enhanced the turnover number (kcat) by four orders of magnitude and the catalytic efficiency (kcat/Km) by three orders of magnitude. These results strongly suggest that the favorable interaction between the aromatic rings of surfactant tails and the hydrophobic residues around the active site of enzyme may help BSLPL maintain highly active open conformation in organic solvent.
- Oh, Yeonock
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p. 1093 - 1097
(2019/11/05)
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- Esterification of Tertiary Amides by Alcohols Through C?N Bond Cleavage over CeO2
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CeO2 has been found to promote ester forming alcoholysis reactions of tertiary amides. The present catalytic system is operationally simple, recyclable, and it does not require additives. The esterification process displays a wide substrate scope (>45 examples; up to 93 % isolated yield). Results of a density functional theory (DFT) study combined with in situ FT-IR observations indicate that the process proceeds through rate limiting addition of a CeO2 lattice oxygen to the carbonyl group of the adsorbed acetamide species with energy barrier of 17.0 kcal/mol. This value matches well with experimental value (17.9 kcal/mol) obtained from analysis of the Arrhenius plot. Further studies by in situ FT-IR and temperature programmed desorption using probe molecules demonstrate that both acidic and basic properties are important, and consequently, CeO2 showed the best performance for the C?N bond cleavage reaction.
- Toyao, Takashi,Nurnobi Rashed, Md.,Morita, Yoshitsugu,Kamachi, Takashi,Hakim Siddiki,Ali, Md. A.,Touchy,Kon, Kenichi,Maeno, Zen,Yoshizawa, Kazunari,Shimizu, Ken-ichi
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p. 449 - 456
(2018/09/11)
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- CALB immobilized onto magnetic nanoparticles for efficient kinetic resolution of racemic secondary alcohols: Long-term stability and reusability
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In this study, an immobilization strategy for magnetic cross-linking enzyme aggregates of lipase B from Candida antarctica (CALB) was developed and investigated. Magnetic particles were prepared by conventional co-precipitation. The magnetic nanoparticles were modified with 3-aminopropyltriethoxysilane (APTES) to obtain surface amino-functionalized magnetic nanoparticles (APTES–Fe3O4) as immobilization materials. Glutaraldehyde was used as a crosslinker to covalently bind CALB to APTES–Fe3O4. The optimal conditions of immobilization of lipase and resolution of racemic 1-phenylethanol were investigated. Under optimal conditions, esters could be obtained with conversion of 50%, enantiomeric excess of product (eep) > 99%, enantiomeric excess of substrate (ees) > 99%, and enantiomeric ratio (E) > 1000. The magnetic CALB CLEAs were successfully used for enzymatic kinetic resolution of fifteen secondary alcohols. Compared with Novozym 435, the magnetic CALB CLEAs exhibited a better enantioselectivity for most substrates. The conversion was still greater than 49% after the magnetic CALB CLEAs had been reused 10 times in a 48 h reaction cycle; both ees and eep were close to 99%. Furthermore, there was little decrease in catalytic activity and enantioselectivity after being stored at ?20 ?C for 90 days.
- Xing, Xiu,Jia, Jun-Qi,Zhang, Jing-Fan,Zhou, Zi-Wen,Li, Jun,Wang, Na,Yu, Xiao-Qi
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- Electrochemical anion pool synthesis of amides with concurrent benzyl ester synthesis
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An electrosynthesis method for amide bond formation has been developed in an attempt to increase the atom economy for this class of reactions. This "anion pool" method electrochemically generates strong nucleophiles from amine substrates. The amine nucleophiles then react with acid anhydrides to generate amides, and the by-product from this reaction undergoes further chemical transformations to generate pharmaceutically relevant benzoic esters. These one-pot reactions are operationally simple, are performed at room temperature, and avoid rare transition metals and added bases. The amide synthesis is amenable to primary and secondary amines and a variety of anhydrides with yields up to 90% obtained. Atom economy and process mass index (PMI) values calculated for this procedure indicate that this process can be considered greener compared to traditional amide synthesis routes used by industry. Furthermore, this electrochemical approach showed unique selectivity when substrates that contained two inequivalent amine moieties were examined.
- Mevan Dissanayake,Melville, Alex D.,Vannucci, Aaron K.
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supporting information
p. 3165 - 3171
(2019/06/18)
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Bu 4 NI-Catalyzed C-C Bond Cleavage and Oxidative Esteri??cation of Allyl Alcohols with Toluene Derivatives
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A novel oxidative esterification of 1-arylprop-2-en-1-ols with toluene derivatives catalyzed by tetrabutylammonium iodide (TBAI) is reported. The optimization of the reaction conditions illustrates that each of experiment parameters including the catalyst, solvent, and oxidant is significant for present oxidative functionalization. This metal-free protocol has a broad substrate scope including the halogen groups for further functionalization and enriches the reactivity profile of allyl alcohol and toluene derivatives. In addition, this protocol represents a new transformation of allyl alcohol involving C-C bond cleavage and C-O bond forming.
- Chen, Yaoyao,Cui, Yongmei,Jia, Xueshun,Li, Chengliang,Li, Jian,Sun, Mingming
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p. 3667 - 3674
(2019/09/30)
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- Nanolayered cobalt-molybdenum sulphides (Co-Mo-S) catalyse borrowing hydrogen C-S bond formation reactions of thiols or H2S with alcohols
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Nanolayered cobalt-molybdenum sulphide (Co-Mo-S) materials have been established as excellent catalysts for C-S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds, nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co-Mo-S-mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the thioetherification of alcohols with hydrogen sulphide (H2S) to furnish symmetrical thioethers has also been developed using these earth-abundant metal-based sulphide catalysts.
- Corma, Avelino,Sorribes, Iván
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p. 3130 - 3142
(2019/03/13)
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- Overriding Traditional Electronic Effects in Biocatalytic Baeyer-Villiger Reactions by Directed Evolution
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Controlling the regioselectivity of Baeyer-Villiger (BV) reactions remains an ongoing issue in organic chemistry, be it by synthetic catalysts or enzymes of the type Baeyer-Villiger monooxygenases (BVMOs). Herein, we address the challenging problem of switching normal to abnormal BVMO regioselectivity by directed evolution using three linear ketones as substrates, which are not structurally biased toward abnormal reactivity. Upon applying iterative saturation mutagenesis at sites lining the binding pocket of the thermostable BVMO from Thermocrispum municipale DSM 44069 (TmCHMO) and using 4-phenyl-2-butanone as substrate, the regioselectivity was reversed from 99:1 (wild-type enzyme in favor of the normal product undergoing 2-phenylethyl migration) to 2:98 in favor of methyl migration when applying the best mutant. This also stands in stark contrast to the respective reaction using the synthetic reagent m-CPBA, which provides solely the normal product. Reversal of regioselectivity was also achieved in the BV reaction of two other linear ketones. Kinetic parameters and melting temperatures revealed that most of the evolved mutants retained catalytic activity, as well as thermostability. In order to shed light on the origin of switched regioselectivity in reactions of 4-phenyl-2-butanone and phenylacetone, extensive QM/MM and MD simulations were performed. It was found that the mutations introduced by directed evolution induce crucial changes in the conformation of the respective Criegee intermediates and transition states in the binding pocket of the enzyme. In mutants that destabilize the normally preferred migration transition state, a reversal of regioselectivity is observed. This conformational control of regioselectivity overrides electronic control, which normally causes preferential migration of the group that is best able to stabilize positive charge. The results can be expected to aid future protein engineering of BVMOs.
- Li, Guangyue,Garcia-Borràs, Marc,Fürst, Maximilian J. L. J.,Ilie, Adriana,Fraaije, Marco W.,Houk,Reetz, Manfred T.
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supporting information
p. 10464 - 10472
(2018/08/03)
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- Ester Synthesis in Water: Mycobacterium smegmatis Acyl Transferase for Kinetic Resolutions
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The acyl transferase from Mycobacterium smegmatis (MsAcT) catalyses transesterification reactions in aqueous media because of its hydrophobic active site. Aliphatic cyanohydrin and alkyne esters can be synthesised in water with excellent and strikingly opposite enantioselectivity [(R);E>37 and (S);E>100, respectively]. When using this enzyme, the undesired hydrolysis of the acyl donor is an important factor to take into account. Finally, the choice of acyl donor can significantly influence the obtained enantiomeric excesses. (Figure presented.).
- de Leeuw, Nicolas,Torrelo, Guzman,Bisterfeld, Carolin,Resch, Verena,Mestrom, Luuk,Straulino, Emanuele,van der Weel, Laura,Hanefeld, Ulf
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p. 242 - 249
(2017/11/16)
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- Lipase-mediated selective acetylation of primary alcohols in ethyl acetate
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An environmental friendly process to selectively acetylate primary alcohols was demonstrated. The esterification process consists of treatment of a primary alcohol in the presence of immobilized C. antarctica lipase (Novozyme-435) in ethyl acetate at room temperature. Primary alcohols were acetylated in the presence of secondary alcohols and phenols.
- de Souza, Ernane C.,Romero-Ortega, Moises,Olivo, Horacio F.
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supporting information
p. 287 - 290
(2017/12/29)
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