- Heterogeneous Metal–Organic-Framework-Based Biohybrid Catalysts for Cascade Reactions in Organic Solvent
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In cooperative catalysis, the combination of chemo- and biocatalysts to perform one-pot reactions is a powerful tool for the improvement of chemical synthesis. Herein, UiO-66-NH2 was employed to stepwise immobilize Pd nanoparticles (NPs) and Candida antarctica lipase B (CalB) for the fabrication of biohybrid catalysts for cascade reactions. Distinct from traditional materials, UiO-66-NH2 has a robust but tunable structure that can be utilized with a ligand exchange approach to adjust its hydrophobicity, resulting in excellent catalyst dispersity in diverse reaction media. These attractive properties contribute to the formation of MOF-based biohybrid catalysts with high activity and selectivity in the synthesis of benzyl hexanoate from benzaldehyde and ethyl hexanoate. With this proof-of-concept, we reasonably expect that future tailor-made MOFs can combine other catalysts, ranging from chemical to biological catalysts for applications in industry.
- Wang, Yangxin,Zhang, Ningning,Zhang, En,Han, Yunhu,Qi, Zhenhui,Ansorge-Schumacher, Marion B.,Ge, Yan,Wu, Changzhu
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Read Online
- Hierarchically structured Beta zeolites with intercrystal mesopores and the improved catalytic properties
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Hierarchical Beta zeolite with mesoporous/microporous structure was synthesized by employing a bifunctionalized amphiphilic surfactant. N 2 adsorption-desorption isotherms indicated the presence of hierarchical mesopores in this sample. Transmission electron microscopy images confirmed the co-presence of ordered micropores and hierarchical mesopores. This sample exhibited excellent hydrothermal stability. In addition, the prepared hierarchically structured Beta zeolite showed greatly enhanced catalytic activity as compared with conventional counterpart for probe reaction involving large molecules due to the highly mesoporous structure, in which diffusion constraints of reactant molecules are the main concern. Such hierarchical micro/mesostructure Beta zeolite combined good hydrothermal stability and high activities may find potential applications in catalysis and adsorption involving bulky molecules.
- Liu, Baoyu,Zheng, Liming,Zhu, Zhihong,Li, Chao,Xi, Hongxia,Qian, Yu
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Read Online
- 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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- 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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p. 11088 - 11091
(2021/10/30)
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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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- Method for hydrogenolysis of halides
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The invention discloses a method for hydrogenolysis of halides. The invention discloses a preparation method of a compound represented by a formula I. The preparation method comprises the following step: in a polar aprotic solvent, zinc, H2O and a compound represented by a formula II are subjected to a reaction as shown in the specification, wherein X is halogen; Y is -CHRR or R; hydrogenin H2O exists in the form of natural abundance or non-natural abundance. According to the preparation method, halide hydrogenolysis can be simply, conveniently and efficiently achieved through a simple and mild reaction system, and good functional group compatibility and substrate universality are achieved.
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- An effective cis-β-octahedral Mn(iii) SALPN catalyst for the Mukaiyama-Isayama hydration of α,β-unsaturated esters
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Two cis-β-MnIIISALPN catalysts were synthesised and tested in the Mukaiyama-Isayama hydration of α,β-unsaturated esters. The MnIIIEtOSALPN(acac) complex 7 is the most active and catalyses hydration with little or no detectable undesired alkene reduction. This catalyst is superior for alkene hydration compared to the originally reported Mn(dpm)3 catalyst.
- Donnelly, Paul S.,North, Andrea J.,Radjah, Natalia Caren,Ricca, Michael,Robertson, Angus,White, Jonathan M.,Rizzacasa, Mark A.
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supporting information
p. 7699 - 7702
(2019/07/09)
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- Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
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The general dehalogenation of alkyl halides with zinc using D2O or H2O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.
- Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
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p. 13841 - 13857
(2019/10/17)
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- Formyloxyacetoxyphenylmethane and 1,1-diacylals as versatile O-formylating and O-acylating reagents for alcohols
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Formyloxyacetoxyphenylmethane, symmetric 1,1-diacylals and mixed 1-pivaloxy-1-acyloxy-1-phenylmethanes have been used as moisture stable O-formylating and O-acylating reagents for primary and secondary alcohols, allylic alcohols and phenols under solvent/catalyst free conditions to afford their corresponding esters in good yield.
- Chapman, Robert S.L.,Francis, Molly,Lawrence, Ruth,Tibbetts, Joshua D.,Bull, Steven D.
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p. 6442 - 6452
(2018/10/02)
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- RUTHENIUM COMPLEXES AND THEIR USES AS CATALYSTS IN PROCESSES FOR FORMATION AND/OR HYDROGENATION OF ESTERS, AMIDES AND RELATED REACTIONS
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The present invention relates to novel Ruthenium complexes of formulae A1-A4 and their use, inter alia, for (1) dehydrogenative coupling of alcohols to esters; (2) hydrogenation of esters to alcohols (including hydrogenation of cyclic esters (lactones) or cyclic di-esters (di-lactones), or polyesters); (3) preparing amides from alcohols and amines—(including the preparation of polyamides (e.g., polypeptides) by reacting dialcohols and diamines and/or polymerization of amino alcohols and/or forming cyclic dipeptides from p-aminoalcohols; (4) hydrogenation of amides (including cyclic dipeptides, polypeptides and polyamides) to alcohols and amines; (5) hydrogenation of organic carbonates (including polycarbonates) to alcohols or hydrogenation of carbamates (including polycarbamates) or urea derivatives to alcohols and amines; (6) dehydrogenation of secondary alcohols to ketones; (7) amidation of esters (i.e., synthesis of amides from esters and amines); (8) acylation of alcohols using esters; (9) coupling of alcohols with water and a base to form carboxylic acids; and (10) preparation of amino acids or their salts by coupling of amino alcohols with water and a base. The present, invention further relates to the use of certain known Ruthenium complexes for the preparation of amino acids or their salts from amino alcohols.
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- Copper-Catalyzed Alkoxycarbonylation of Alkanes with Alcohols
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Esters are important chemicals widely used in various areas, and alkoxycarbonylation represents one of the most powerful tools for their synthesis. In this communication, a new copper-catalyzed carbonylative procedure for the synthesis of aliphatic esters from cycloalkanes and alcohols was developed. Through direct activation of the C sp3 ?H bond of alkanes and with alcohols as the nucleophiles, the desired esters were prepared in moderate-to-good yields. Paraformaldehyde could also be applied for in situ alcohol generation by radical trapping, and moderate yields of the corresponding esters could be produced. Notably, this is the first report on copper-catalyzed alkoxycarbonylation of alkanes.
- Li, Yahui,Wang, Changsheng,Zhu, Fengxiang,Wang, Zechao,Dixneuf, Pierre H.,Wu, Xiao-Feng
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p. 1341 - 1345
(2017/04/14)
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- Synthesis of ZSM-5 monoliths with hierarchical porosity through a steam-assisted crystallization method using sponges as scaffolds
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Self-supporting ZSM-5 crystals with hierarchical porosity were prepared through a steam-assisted crystallization method using sponges as rigid scaffolds. The synthesized materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, solid-state nuclear magnetic resonance spectroscopy and ammonia temperature-programmed desorption. The ZSM-5 monoliths exhibited high crystallinities, hierarchical porous structures and strong acidities. They showed superior catalytic performance in the liquid-phase esterification reaction between benzyl alcohol and hexanoic acid.
- Hu, Tiejing,Liu, Jian,Cao, Changyan,Song, Weiguo
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p. 872 - 877
(2017/05/22)
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- Esterification of the Primary Benzylic C-H Bonds with Carboxylic Acids Catalyzed by Ionic Iron(III) Complexes Containing an Imidazolinium Cation
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The first iron-catalyzed esterification of the primary benzylic C-H bonds with carboxylic acids using di-tert-butyl peroxide as an oxidant is achieved by novel ionic iron(III) complexes containing an imidazolinium cation. The use of well-defined, air-stable, and available iron(III) complex in a 5 mol % loading and readily available starting materials with a broad generality and outstanding sterically hindered tolerance renders this methodology a useful alternative to other protocols that are typically employed for the synthesis of benzyl esters.
- Lu, Bing,Zhu, Fan,Sun, Hong-Mei,Shen, Qi
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supporting information
p. 1132 - 1135
(2017/03/14)
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- Transfer Hydro-dehalogenation of Organic Halides Catalyzed by Ruthenium(II) Complex
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A simple and efficient Ru(II)-catalyzed transfer hydro-dehalogenation of organic halides using 2-propanol solvent as the hydride source was reported. This methodology is applicable for hydro-dehalogenation of a variety of aromatic halides and α-haloesters and amides without additional ligand, and quantitative yields were achieved in many cases. The potential synthetic application of this method was demonstrated by efficient gram-scale transformation with catalyst loading as low as 0.5 mol %.
- You, Tingjie,Wang, Zhenrong,Chen, Jiajia,Xia, Yuanzhi
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p. 1340 - 1346
(2017/02/10)
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- Oxidative Alkane C?H Alkoxycarbonylation
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Directly utilizing a chemical feedstock to construct valuable compounds is an attractive prospect in organic synthesis. In particular, the combination of C(sp3)?H activation and oxidative carbonylation involving alkanes and CO gas is a promising and efficient method to synthesize carbonyl derivatives. However, due to the high C?H bond dissociation energy and low polarity of unactivated alkanes, the carbonylation of unactivated C(sp3)?H bonds still remains a great challenge. In this work, we introduce a palladium-catalyzed radical oxidative alkoxycarbonylation of alkanes to prepare numerous alkyl carboxylates. Various alkanes and alcohols were compatible, generating the desired products in up to 94 % yield. Remarkably, ethane, a constituent of natural gas, could be employed as a substrate under the standard reaction conditions. Preliminary mechanistic studies revealed a probable palladium-catalyzed radical process.
- Lu, Lijun,Shi, Renyi,Liu, Luyao,Yan, Jingwen,Lu, Fangling,Lei, Aiwen
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supporting information
p. 14484 - 14488
(2016/10/03)
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- 1,4-Bis-Dipp/Mes-1,2,4-Triazolylidenes: Carbene Catalysts That Efficiently Overcome Steric Hindrance in the Redox Esterification of α- And β-Substituted α,β-Enals
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As reported by Scheidt and Bode in 2005, sterically nonencumbered α,β-enals are readily converted to saturated esters in the presence of alcohols and N-heterocyclic carbene catalysts, e.g., benzimidazolylidenes or triazolylidenes. However, substituents at the α- or β-position of the α,β-enal substrate are typically not tolerated, thus severely limiting the substrate spectrum. On the basis of our earlier mechanistic studies, a set of N-Mes- or N-Dipp-substituted 1,2,4-triazolium salts were synthesized and evaluated as (pre)catalysts in the redox esterification of various α- or β-substituted enals. In particular the 1,4-bis-Mes/Dipp-1,2,4-triazolylidenes overcome the above limitations and efficiently catalyze the redox esterification of a whole series of α/β-substituted enals hitherto not amenable to NHC-catalyzed transformations. The synthetic value of 1,4-bis-Mes/Dipp-1,2,4-triazolylidenes is further demonstrated by the one-step bicyclization of 10-oxocitral to (racemic) nepetalactone in diastereomerically pure form.
- Yatham, Veera Reddy,Harnying, Wacharee,Kootz, Darius,Neud?rfl, J?rg-M.,Schl?rer, Nils E.,Berkessel, Albrecht
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supporting information
p. 2670 - 2677
(2016/03/12)
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- Unique Chemoselective Hydrogenation using a Palladium Catalyst Immobilized on Ceramic
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A heterogeneous palladium catalyst supported on a ceramic (5 % Pd/ceramic) was developed. The catalyst exhibited a specific chemoselectivity for hydrogenation that has never been achieved by other palladium-catalyzed methods. Either aliphatic or aromatic N-Cbz groups could be deprotected to the corresponding free-amines, while the hydrogenolysis of benzyl esters and ethers did not proceed. Furthermore, aryl chlorides and epoxides were tolerant under the Pd/ceramic-catalyzed hydrogenation conditions. 5 % Pd/ceramic could be reused without any loss of catalyst activity, as no palladium leaching was detected in the reaction media.
- Monguchi, Yasunari,Marumoto, Takahisa,Ichikawa, Tomohiro,Miyake, Yutaka,Nagae, Yoshiyuki,Yoshida, Michiyuki,Oumi, Yasunori,Sawama, Yoshinari,Sajiki, Hironao
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p. 2155 - 2160
(2015/11/24)
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- Versatile and sustainable alcoholysis of amides by a reusable CeO 2 catalyst
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CeO2 catalyzed the esterification between an equivalent molar ratio of primary amides and alcohols under neutral conditions, which provides the first versatile reusable catalytic system for direct alcoholysis of amides to esters with wider scope and 67 times higher turnover number (TON) than previous catalytic systems.
- Siddiki, S. M. A. Hakim,Touchy, Abeda Sultana,Tamura, Masazumi,Shimizu, Ken-Ichi
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p. 35803 - 35807
(2014/11/07)
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- Scandium triflate catalyzed ester synthesis using primary amides
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A scandium triflate (ScOTf)3 catalyzed methodology has been developed to synthesize esters from primary amides. Various primary and secondary aliphatic alcohols have been shown to react in n-heptane with a range of primary amides for 24 h.
- Atkinson, Benjamin N.,Williams, Jonathan M.J.
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supporting information
p. 6935 - 6938
(2015/01/16)
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- Effect of synthesis conditions on the structural and catalytic properties of hierarchically structured ZSM-5 zeolites
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Hierarchically structured ZSM-5 zeolites were synthesized by employing only one dual-porogenic surfactant, and the hydrothermal crystallization of hierarchical structured zeolites were investigated under rotating and static synthesis conditions. X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms, 27Al magic-angle spinning nuclear magnetic resonance (27Al MAS NMR) and thermogravimetric analysis (TGA) were used to characterize the structural and textural features of the resultant zeolite products. By tuning the synthesis conditions from rotating to static, the morphology of the as-obtained hierarchical structure ZSM-5 zeolites changed from silk-like to nanoparticles with a disordered arrangement. Furthermore, the obtained zeolites under static conditions showed a higher BET surface area and lower total pore volume than those of zeolites synthesized under rotating conditions. In addition, quantum chemical calculation results show that the inner ammonium groups may have greater contribution in directing the zeolite structure than tailed ammonium groups. More importantly, the hierarchical structured ZSM-5 zeolites synthesized under static conditions exhibited a higher benzyl alcohol conversion rate and lower ester selectivity compared to those of the samples prepared under rotating conditions. Consideration of the effects of synthesis conditions may be useful for modulating the textural and catalytic properties of hierarchical zeolites.
- Liu, Baoyu,Zheng, Liming,Zhu, Zhihong,Zhang, Kai,Xi, Hongxia,Qian, Yu
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p. 13831 - 13838
(2014/04/17)
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- Recyclable hypervalent iodine(III) reagent iodosodilactone as an efficient coupling reagent for direct esterification, amidation, and peptide coupling
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A hypervalent iodine(III) reagent plays a novel role as an efficient coupling reagent to promote the direct condensation between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, amides, as well as peptides without racemization. The regeneration of iodosodilactone (1) can also be readily achieved. The intermediate acyloxyphosphonium ion C from the activation of a carboxylic acid is thought to be involved in the present esterification reaction.
- Tian, Jun,Gao, Wen-Chao,Zhou, Dong-Mei,Zhang, Chi
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supporting information; experimental part
p. 3020 - 3023
(2012/08/07)
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- Umpolung reactions in an ionic liquid catalyzed by electrogenerated N-heterocyclic carbenes. Synthesis of saturated esters from activated α,β-unsaturated aldehydes
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The umpolung reaction of α,β-unsaturated aldehydes to saturated esters has been carried out in an ionic liquid by organocatalysis of electrogenerated NHC. The roles of solvent, precatalyst and proton donor of the ionic liquid have been verified and good to high yields of esters have been obtained using a "green" and mild methodology.
- Feroci, Marta,Chiarotto, Isabella,Orsini, Monica,Pelagalli, Romina,Inesi, Achille
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supporting information; experimental part
p. 5361 - 5363
(2012/06/30)
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- Oxidation of primary aliphatic and aromatic aldehydes with difluoro(aryl)-λ3-bromane
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Oxidation of primary aliphatic aldehydes with p- trifluoromethylphenyl(difluoro)-λ3-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses.
- Ochiai, Masahito,Yoshimura, Akira,Hoque, Md. Mahbubul,Okubo, Takuji,Saito, Motomichi,Miyamoto, Kazunori
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supporting information; experimental part
p. 5568 - 5571
(2011/12/03)
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- α-Aroyloxyaldehydes: Scope and limitations as alternatives to α-haloaldehydes for NHC-catalysed redox transformations
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α-Aroyloxyaldehydes are readily prepared bench stable synthetic intermediates. Their ability to act as α-haloaldehyde surrogates for NHC-promoted redox esterifications and in [4+2] cycloadditions is described.
- Ling, Kenneth B.,Smith, Andrew D.
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supporting information; experimental part
p. 373 - 375
(2011/02/24)
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- Assessment of the catalytic activities of novel broensted acidic ionic liquid catalysts
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Broensted acidic ionic liquids (BILs) were synthesized by a two step synthetic protocol. Catalytic activities of BILs were assessed by means of suitable catalytic reactions such as acylation of 2-methoxynapthalene with acetic anhydride, Biginelli reaction to synthesize 3,4-dihydropyrimidin-2(1H)- one, stereoselective synthesis of β-amino ketone via direct Mannich-type reaction and esterification of hexanoic acid with benzyl alcohol. Catalytic activities of BILs were high when compared with those of solid acid catalysts such as ZSM-5, beta, dealuminated beta and Al-SBA-15. BILs catalysts were found to be highly stereo/regio-selective for above mentioned reactions. Novel BILs catalyst offers several attractive features such as low cost, high catalytic activity/selectivity and recyclability. Graphical Abstract: N-methylimidazole and pyridine derived Broensted acidic ionic liquids were found to be highly active and stereo/regio-selective compared to various solid acid catalysts in fine chemicals (1-5) synthesis.[Figure not available: see fulltext.]
- Srivastava, Rajendra
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experimental part
p. 17 - 25
(2010/12/25)
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- Template synthesis of ordered mesoporous organic polymeric materials using hydrophobic silylated KIT-6 mesoporous silica
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Porous organic materials can be synthesized via free-radical polymerization of crosslinkable olefinic monomers within the interstices of porous templates. The synthesis process has been employed to generate ordered mesoporous structures through use of a mesoporous silica template, KIT-6. The mesoporous silica features a bicontinuously mesoporous structure belonging to the cubic Ia3d space group. Pore diameters of the silica could be varied over the range 3.6-7.3 nm by varying the synthesis conditions, while maintaining a constant pore wall thickness of 3.7 nm. The polymerization reaction proceeded with heating at 150 °C after initiation with α,α′- azobisisobutyronitrile. The resultant polymeric materials were characterized after template extraction using hydrofluoric acid. Characterization results demonstrated that the polymeric materials retained a cubic Ia3d mesoporous structure only when the template pore diameters exceeded 5 nm, even if highly crosslinkable monomers, such as divinylbenzene, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, were incorporated. The polymeric structure collapsed unless the template pore diameters were sufficiently larger than the distance between crosslinking points. In addition, structural integrity was maintained only if the mesopore walls were hydrophobically functionalized via silylation. Under optimal replication conditions, the ordered mesoporous polymeric materials exhibited a very narrow pore size distribution and a high specific surface area (619 m2 g-1) that reflected the qualities of the original silica template. Such mesoporous polymeric materials could be functionalized via copolymerization with other functional monomers or via organic reactions. The functionalized mesoporous polymers are suitable for catalytic and adsorption applications because the porous structures feature a high surface area and excellent functional group density.
- Choi, Dae-Heung,Ryoo, Ryong
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scheme or table
p. 5544 - 5550
(2011/08/06)
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- Samarium diiodide as an efficient catalyst for the conversion of N-acyloxazolidinones into esters
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The transformation of N-acyloxazolidinones into esters is readily performed using catalytic amounts of samarium diiodide in tetrahydrofuran at room temperature. This method allows the isolation of various esters without racemization in the case of scalemi
- Magnier-Bouvier, Caroline,Reboule, Iréna,Gil, Richard,Collin, Jacqueline
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scheme or table
p. 1211 - 1215
(2009/04/06)
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- Protonation of homoenolate equivalents generated by N-heterocyclic carbenes
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Homoenolate equivalents are generated by Lewis basic N-heterocyclic carbene catalysts and then protonated to generate efficiently saturated esters from unsaturated aldehydes. This reactivity is extended to the generation of β-acylvinyl anions from alkynyl aldehydes. The asymmetric protonation of a homoenolate equivalent generated from a β,β-disubstituted aldehyde can be accomplished with a chiral N-heterocyclic carbene. Georg Thieme Verlag Stuttgart.
- Maki, Brooks E.,Chan, Audrey,Scheidt, Karl A.
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p. 1306 - 1315
(2008/12/22)
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- Mesoporous materials with zeolite framework: Remarkable effect of the hierarchical structure for retardation of catalyst deactivation
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Hierarchical MFI zeolite was synthesized following a synthesis route using organic-inorganic hybrid surfactants; the resultant zeolite with mesoporous/microporous hierarchical structure exhibited remarkably high resistance to deactivation in catalytic activity of various reactions such as isomerization of 1,2,4-trimethylbenzene, cumene cracking, and esterification of benzyl alcohol with hexanoic acid, as compared with conventional MFI and mesoporous aluminosilicate MCM-41. The Royal Society of Chemistry 2006.
- Srivastava, Rajendra,Choi, Minkee,Ryoo, Ryong
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p. 4489 - 4491
(2008/09/19)
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- Chemoselective hydrogenation method catalyzed by Pd/C using diphenylsulfide as a reasonable catalyst poison
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While Pd/C is one of the most useful catalysts for hydrogenation, the high catalyst activity of Pd/C causes difficulty in its application to chemoselective hydrogenation between different types of reducible functionalities. In order to achieve chemoselective hydrogenation using Pd/C, we investigated catalyst poison as a controller of the catalyst activity. We found that the addition of Ph2S (diphenylsulfide) to the Pd/C-catalyzed hydrogenation reaction mixture led to reasonable deactivation of Pd/C. By the use of the Pd/C-Ph2S catalytic system, olefins, acetylenes, and azides can be selectively reduced in the coexistence of aromatic carbonyls, aromatic halides, cyano groups, benzyl esters, and N-Cbz (benzyloxycarbonyl) protecting groups. The present method is promising as a general and practical chemoselective hydrogenation process in synthetic organic chemistry.
- Mori, Akinori,Mizusaki, Tomoteru,Miyakawa, Yumi,Ohashi, Eri,Haga, Tomoko,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
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p. 11925 - 11932
(2007/10/03)
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- Pd/C-catalyzed chemoselective hydrogenation in the presence of diphenylsulfide
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A Pd/C-catalyzed chemoselective hydrogenation using diphenylsulfide as a catalyst poison has been developed. This methodology selectively hydrogenates olefin and acetylene functionalities without hydrogenolysis of aromatic carbonyls and halogens, benzyl esters, and N-Cbz protective groups.
- Mori, Akinori,Miyakawa, Yumi,Ohashi, Eri,Haga, Tomoko,Maegawa, Tomohiro,Sajiki, Hironao
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p. 3279 - 3281
(2007/10/03)
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- Conversion of α,β-unsaturated aldehydes into saturated esters: An umpolung reaction catalyzed by nucleophilic carbenes
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(Chemical Equation Presented) N-Heterocyclic carbenes derived from benzimidazolium salts are effective catalysts for generating homoenolate species from α,β-unsaturated aldehydes. These nucleophilic intermediates can be protonated, and the resulting activated carbonyl unit is trapped with an alcohol nucleophile, thereby promoting a highly efficient conversion of an α,β-unsaturated aldehyde into a saturated ester. A kinetic resolution of secondary alcohols can be achieved using chiral imidazoylidene catalysts.
- Chan, Audrey,Scheidt, Karl A.
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p. 905 - 908
(2007/10/03)
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- Process for the preparation of carboxylic benzyl esters
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Carboxylic benzyl esters can be prepared by reacting benzyl chloride with carboxylic acids in the presence of one or more quaternary ammonium carboxylates as catalyst.
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- 2-Chloro-1,3-dimethylimidazolinium chloride. 1. A powerful dehydrating equivalent to DCC
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2-Chloro-1,3-dimethylimidazolinium chloride (DMC) (3) can act as a powerful dehydrating agent, replacing DCC (1) under nearly neutral conditions. Its application to acylation and dehydration is described.
- Isobe, Toshio,Ishikawa, Tsutomu
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p. 6984 - 6988
(2007/10/03)
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- An improved method for preparation of carboxylic esters using CsF- celite/alkyl halide/CH3CN combination
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A new method for efficient and chemoselective esterification of carboxylic acids in CsF-Celite/alkyl halide/CH3CN reaction system is described.
- Lee, Jong Chan,Choi, Youngsup
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p. 2021 - 2026
(2007/10/03)
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- Syntheses of long-chain quaternary ammonium salts from fatty alcohols by microwave irradiation
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The phase-transfer catalysts, long-chain quaternary ammonium salts, were rapidly synthesized from fatty alcohols by the reactions with hydrogen halides in the presence of trialkyl amines under microwave irradiation. The catalysts could be widely applied in a variety of quick and new organic reactions, whether by conventional heating or under microwave irradiation. The reaction efficiencies under microwave irradiation were higher than those obtained with conventional heating.
- Jiang,Hu,Pang,Yuan
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p. 847 - 850
(2007/10/03)
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- Regioselective Oxidative Cleavage of Functionalized Unsymmetric Tetraalkylstannanes via Ozone
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The direct oxidation of (α-alkoxyalkyl)trialkylstannanes to esters by reaction with ozone is described.
- Linderman, Russell J.,Jaber, Mohamed
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p. 5993 - 5996
(2007/10/02)
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- Microwave irradiation promoted reactions of carboxylic acids with halides in the presence of quarternary ammonium salt
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The reactions of carboxylic acids with halides which could not take place by conventional heating are promoted by microwave irradiation in the presence of quaternary ammonium salt as a catalyst, without a base.
- Yuan,Jiang,Gao
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p. 3109 - 3114
(2007/10/02)
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- A Novel Transesterification of Thioesters with Alcohols by an Electrochemical Activation
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Esters were synthesized from thioesters and alcohols in high yields by an electrochemical activation.Different results were obtained by the use of n-Bu4N+ I- and LiBF4 as the electrolyte.
- Yamaguchi, Masahiko,Tsukamoto, Yukiharu,Minami, Toru
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p. 1223 - 1226
(2007/10/02)
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- Esterification of Carboxylic Acids by Alcohols with 2-Chloro-1,3,5-trinitrobenzene as Condensing Agent
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When mixtures of carboxylic acids or their sodium salts and alcohols were treatment with 2-chloro-1,3,5-trinitrobenzene in the presence of pyridine under mild conditions, the corresponding carboxylic esters were formed.The yields and the rates of the ester formation depended on the types of the acids and the alcohols used.
- Takimoto, Seiji,Inanaga, Junji,Katsuki, Tsutomu,Yamaguchi, Masaru
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p. 1470 - 1473
(2007/10/02)
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- A USEFUL METHOD FOR SELECTIVE ACYLATION OF ALCOHOLS USING 2,2'-BIPYRIDYL-6-YL CARBOXYLATE AND CESIUM FLUORIDE
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Primary and secondary alcohols are acylated under mild conditions by the of use 2,2'-bipyridyl-6-yl carboxylates and cesium fluoride.Furthermore, the reaction is successfully applied to selective acylation of a primary carbinol group of diols containing primary and secondary carbinol groups or exclusive O-acylation of aromatic amino alcohols.
- Mukaiyama, Teruaki,Pai, Fong-Chang,Onaka, Makoto,Narasaka, Koichi
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p. 563 - 566
(2007/10/02)
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- Process for the preparation of a carboxylic acid ester
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An improved and novel process for the preparation of a carboxylic acid ester which comprises reacting a carboxylic acid with an alcohol or a sulfenic acid ester thereof in the presence of a tertiary phosphine and a disulfide of a mercaptoheterocyclic compound containing a nitrogen-carbon double bond with which the disulfide linkage is conjugated.
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