- Investigations into the C-deuteriation of enol acetates derived from aryl alkyl ketones
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Results are reported on the regioselective C-deuteriation of a series of enol acetates (derived from the aryl alkyl ketones) using molecular deuterium as the D-source and palladium-on-barium sulphate as the mediator. The results presented highlight potent
- Buksha, Svitlana,Coumbarides, Gregory S.,Dingjan, Marco,Eames, Jason,Suggate, Michael J.,Weerasooriya, Neluka
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- Identification of an Esterase Isolated Using Metagenomic Technology which Displays an Unusual Substrate Scope and its Characterisation as an Enantioselective Biocatalyst
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Evaluation of an esterase annotated as 26D isolated from a marine metagenomic library is described. Esterase 26D was found to have a unique substrate scope, including synthetic transformations which could not be readily effected in a synthetically useful manner using commercially available enzymes. Esterase 26D was more selective towards substrates which had larger, more sterically demanding substituents (i. e. iso-propyl or tert-butyl groups) on the β-carbon, which is in contrast to previously tested commercially available enzymes which displayed a preference for substrates with sterically less demanding substituents (e.g. methyl group) at the β-carbon. (Figure presented.).
- Gavin, Declan P.,Murphy, Edel J.,Foley, Aoife M.,Castilla, Ignacio Abreu,Reen, F. Jerry,Woods, David F.,Collins, Stuart G.,O'Gara, Fergal,Maguire, Anita R.
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supporting information
p. 2466 - 2474
(2019/03/11)
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- DMAP-based flexible polymer networks formed via Heck coupling as efficient heterogeneous organocatalysts
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Two DMAP-based flexible polymer networks TPB-DMAP and TPA-DMAP have been successfully synthesized via palladium catalyzed Heck cross-coupling. The structures of these polymers were confirmed by solid state 13C CP/MAS and Fourier transform infrared spectroscopy (FTIR). Although both polymers have negligible surface areas, they exhibit excellent catalytic efficiency for the acylation of 1-phenylethanol with acetic anhydride due to their good swelling capacities. Utilized as a typical catalyst, the polymer TPA-DMAP shows high activities for acylation of a variety of alcohols to the corresponding esters. Moreover, the catalyst can be recycled at least ten times without obvious loss of catalytic activity.
- Xu, Wei,Xia, Wu,Guan, Yukun,Wang, Yiming,Lu, Cuifen,Yang, Guichun,Nie, Junqi,Chen, Zuxing
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- Chemoenzymatic synthesis of rasagiline mesylate using lipases
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A straightforward chemoenzymatic synthesis of rasagiline mesylate has been developed. The key steps for the introduction of chirality involved kinetic enzymatic resolution with lipases via acetylation of racindanol and an inversion configuration Mitsunobu reaction of the produced (S)-indanol. Immobilized lipase from Thermomyces lanuginosus proved to be a robust biocatalyst in the kinetic resolution, leading to (S)-indanol with high selectivity (e.e. > 99%, E > 200) in just 15 min, at 35°C, in hexane, being reused for ten-times without significant loss of the activity and selectivity.
- De Mattos, Marcos Carlos,De Fonseca, Thiago Sousa,Da Silva, Marcos Reinaldo,De Oliveira, Maria Da Concei??o Ferreira,De Lemos, Telma Leda Gomes,De Marques, Ricardo Araújo
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- CAL-B-Catalyzed Enantioselective Deacetylation of Some Benzylic Acetate Derivatives Via Alcoholysis in Non-aqueous Media
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Enantioselective deacetylation of a set of benzylic acetates via alcoholysis catalyzed by Lipase B from Candida antarctica (CAL-B), under mild conditions is described. A systematic study allows to determine the appropriate combination nucleophile/organic solvent and also to explain the influence of these parameters on the enzymatic catalytic reaction. In all cases, (R)-alcohols are obtained with high ee (up to >99 %) at conversion 36 % 500. The enzymatic reactivity is influenced by the hydrophobicity of solvent and the structure/nature of the nucleophile. Furthermore, CAL-B allows enantio-complementary between transesterifications in non-aqueous media: alcoholysis and acetylation.
- Zadi, Amna,Merabet-Khelassi, Mounia,Aribi-Zouioueche, Louisa
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p. 1054 - 1061
(2015/02/05)
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- Efficient approach for the chemoselective acetylation of alcohols catalyzed by a novel metal oxide nanocatalyst CuO-ZnO
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A new method has been developed for the chemoselective acetylation of alcohols with acetic anhydride in the presence of phenols using a novel, recyclable CuO-ZnO nanocatalyst. The catalyst was synthesized using the co-precipitation method and characterized by N2 adsorption-desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersion scanning analyses. Furthermore, this catalyst could be recycled up to six times without significant loss in its activity.
- Albadi, Jalal,Alihosseinzadeh, Amir,Mardani, Mehdi
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p. 308 - 313
(2015/09/28)
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- Efficient benzylic and aliphatic C-H oxidation with selectivity for methylenic sites catalyzed by a bioinspired manganese complex
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A benzimidazole-based nonheme manganese complex efficiently catalyzes benzylic, aliphatic C-H as well as tertiary C-H oxidation with hydrogen peroxide as the oxidant in the presence of acetic acid as additive. 18O labeling experiments suggest the reaction may proceed via a high-valent manganese-oxo intermediate.
- Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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supporting information
p. 1108 - 1111
(2014/03/21)
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- Allylic oxidation of alkenes catalyzed by a copper-aluminum mixed oxide
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A strategy for the allylic oxidation of cyclic alkenes with a copper-aluminum mixed oxide as catalyst is presented. The reaction involves the treatment of an alkene with a carboxylic acid employing tert-butyl hydroperoxide as the oxidant. In all cases, the corresponding allylic esters are obtained. When l-proline is employed, the allylic alcohol or ketone is obtained. The oxidation of cyclohexene and valencene has been optimized by design of experiments (DoE) statistical methodology.
- Garcia-Cabeza, Ana Leticia,Marin-Barrios, Ruben,Moreno-Dorado, F. Javier,Ortega, Maria J.,Massanet, Guillermo M.,Guerra, Francisco M.
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supporting information
p. 1598 - 1601
(2014/04/17)
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- A green route to enantioenriched (S)-arylalkyl carbinols by deracemization via combined lipase alkaline-hydrolysis/Mitsunobu esterification
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Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a-9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a-9a via an enzymatic hydrolysis, with CAL-B lipase and Na2CO3, in non-aqueous media was optimized and gave high selectivities (E ? 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% ee 99%, in acceptable isolated yields 70% yield 89%, and with some variations according to the acetate structure.
- Houiene, Zahia,Merabet-Khelassi, Mounia,Bouzemi, Nassima,Riant, Olivier,Aribi-Zouioueche, Louisa
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p. 290 - 296
(2013/04/23)
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- Green methodology for enzymatic hydrolysis of acetates in non-aqueous media via carbonate salts
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Herein we report a new approach to enantiomerically enriched acetates using a lipase-catalyzed hydrolysis in non-aqueous media by alkaline carbonate salts. The use of sodium carbonate in the enzymatic hydrolysis with Candida antarctica lipase B (CAL-B) of racemic acetates shows a large enhancement of the reactivity and selectivity of this lipase. The role of the carbonate salts, the amount and the nature of the alkaline earth metal on the efficiency of this new pathway are investigated. The enzymatic kinetic resolution of acetates 1a-9a, by enzymatic-carbonate hydrolysis under mild conditions is described. In all cases, the resulting alcohols and remaining acetates were obtained in high ee values (up to >99%) while the selectivities reached E >500.
- Merabet-Khelassi, Mounia,Houiene, Zahia,Aribi-Zouioueche, Louisa,Riant, Olivier
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experimental part
p. 828 - 833
(2012/09/25)
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- N-acyl 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) tetraphenylborate salts as O-acylating agents
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Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been shown to be effective O-acylating agents, reacting with both primary and secondary alcohols to give the corresponding esters in good yields. In the case of diols, the N-acyl DBN·BPh4 salts have been shown to acylate regioselectively the primary alcohol functionality in the presence of a secondary alcohol. The DBN hydrotetraphenylborate side product can be readily removed by filtration, providing the ester products without the need for further purification.
- Taylor, James E.,Williams, Jonathan M.J.,Bull, Steven D.
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experimental part
p. 4074 - 4076
(2012/08/28)
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- Investigation of catalytic activity of high-valent vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for acetylation of alcohols and phenols with acetic anhydride
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In the present work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V IV(TPP)(OTf)2], in the acetylation of alcohols and phenols with Ac2O is reported. This new V(IV) catalyst was used as an efficient catalyst for not only primary alcohols (benzylic and aliphatic) but also sterically-hindered secondary and tertiary alcohols with acetic anhydride and the corresponding acetates were obtained in 85-99% yield and 0.5-15 min. Acetylation of phenols with acetic anhydride was also performed to afford the desired acetates in 88-99% and 1.5-20 min. This catalyst can be reused several times without loss of its catalytic activity.
- Taghavi, S. Abdolmanaf,Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza
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experimental part
p. 159 - 164
(2011/12/16)
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- Spinel-type zinc aluminate (ZnAl2O4) nanoparticles prepared by the co-precipitation method: A novel, green and recyclable heterogeneous catalyst for the acetylation of amines, alcohols and phenols under solvent-free conditions
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Zinc aluminate (ZnAl2O4) nanoparticles with an average particle size of about 8 nm were easily prepared by the co-precipitation method using aqueous ammonia solution as the precipitating agent. This nanosized spinel-type oxide was characterized by TGA, XRD, FT-IR, TEM, and surface area measurement and used as the heterogeneous catalyst for the acetylation reaction. Efficient acetylation of various amines, alcohols and phenols was carried out over ZnAl2O4 nanoparticles using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature without the use of a solvent. The method is highly selective, allowing the alcoholic hydroxyl group to be protected while the phenolic hydroxyl group remains intact, and the amine group can be acetylated in the presence of the hydroxyl group. This method is fast and has a high yield. It is also clean, safe, cost effective, compatible with substrates that have other functional groups and very suitable for practical organic synthesis. In addition, the catalyst can be reused without significant loss of activity. Indeed, the catalytic activity of the ZnAl2O4 nanoparticles is higher than that of bulk ZnAl2O4.
- Farhadi, Saeid,Panahandehjoo, Somayeh
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scheme or table
p. 293 - 302
(2010/09/04)
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- REACTION SYSTEM
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The invention provides a reaction system comprising: a first reaction promoter capable of converting a first substrate into a first substance; and a plurality of microcapsules, each of said microcapsules comprising a second reaction promoter encapsulated within an encapsulant, said second reaction promoter being capable of converting a second substrate into a second substance. The second substrate is capable of passing through the encapsulant to contact the second reaction promoter and the second substance is capable of passing out of the microcapsules through the encapsulant. In the reaction system, either (a) the first substance is, or is capable of being converted into, the second substrate and, in operation, the conversion of the second substrate by the second reaction promoter occurs to a greater extent than the conversion of the first substrate by the second reaction promoter and the conversion of the second substance by the first reaction promoter is low, or (b) the second substance is, or is capable of being converted into, the first substrate and, in operation, the conversion of the first substrate by the first reaction promoter occurs to a greater extent than the conversion of the second substrate by the first reaction promoter and the conversion of the first substance in the microcapsules is low.
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Page/Page column 5; 19
(2010/04/25)
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- Fluorous 4-N,N-dimethylaminopyridine (DMAP) salts as simple recyclable acylation catalysts
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The use of an easily accessible fluorous salt of DMAP, 1-R, as an active and recyclable acylation catalyst, under simple conditions has been reported. The recyclability of organic- and metal-based catalysts is of prime interest for the development of sustainable synthesis processes. The alcohol and the anhydride were mixed in a 10 mL round-bottomed flask and 1-R was added. The DMAP-catalyzed esterification reaction of an alcohol is performed in nonpolar solvents with an anhydride as the acyl donor, in the presence of a base in stoichiometric amounts. The simplicity of the process (readily accessible catalyst, easy to handle and to recover) makes it an attractive alternative for cleaner and safer acylation reactions, which could be used with asymmetric dialkylaminopyridines, or in other transformations, such as the Baylis Hillman reaction.
- Vuluga, Daniela,Legros, Julien,Crousse, Benoit,Bonnet-Delpon, Daniele
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supporting information; experimental part
p. 1776 - 1779
(2010/06/14)
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- Efficient acetylation of alcohols, phenols, and amines catalyzed by melamine trisulfonic acid (MTSA)
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Melamine trisulfonic acid (MTSA) was easily prepared by the reaction of melamine with neat chlorosulfonic acid at room temperature. This reagent can be used as an efficient catalyst for the acetylation of alcohols, phenols, and amines with Ac2O under mild and completely heterogeneous reaction conditions.
- Shirini, Farhad,Zolfigol, Mohammad Ali,Aliakbar, Ali-Reza,Albadi, Jalal
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experimental part
p. 1022 - 1028
(2010/05/18)
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- Silica-bonded N-propyl sulfamic acid as an efficient catalyst for the formylation and acetylation of alcohols and amines under heterogeneous conditions
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A simple and efficient procedure for the preparation of silica-bonded N-propyl sulfamic acid (SBNPSA) by the reaction of 3-aminopropylsilica (1) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a new catalyst for the formylation of alcohols and amines with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also, SBNPSA catalyzed acetylation of various alcohols and amines with acetic anhydride at room temperature.
- Niknam, Khodabakhsh,Saberi, Dariush
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experimental part
p. 5210 - 5214
(2009/12/06)
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- Copper triflate/t-BuOOAc-catalyzed amidation of allylic and benzylic acetates with sulfonamides
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A copper triflate/t-BuOOAc-catalyzed amidation of allylic and benzylic acetates has been developed which is suitable for the coupling of a wide variety of functionalized sulfonamide nucleophiles with acetate electrophiles. The methodology allows for the amidation of benzylic substrates which are not further activated by an additional adjacent alkene or alkyne, enabling simple allylic acetates and primary benzylic acetates to be used as reaction partners.
- Powell, David A.,Pelletier, Guillaume
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p. 2495 - 2498
(2008/09/19)
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- Transesterification/Acylation of Secondary Alcohols Mediated by N-Heterocyclic Carbene Catalysts
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N-Heterocyclic carbenes (NHC) are efficient catalysts for transesterification/acylation reactions involving secondary alcohols. The catalytic transformations are carried out employing low catalyst loadings in convenient reaction times at room temperature.
- Singh, Rohit,Kissling, Rebecca M.,Letellier, Marie-Anne,Nolan, Steven P.
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p. 209 - 212
(2007/10/03)
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- Lipase-catalyzed Irreversible Transesterification of Secondary Alcohols Using Isopropenyl Acetate
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Asymmetric acetylation of a set of secondary alcohols with the innocuous acyl donor isopropenyl acetate catalyzed by a lipase from Pseudomonas cepacia immobilized on ceramic particles (PSL-C) in toluene as organic medium afforded the chiral alcohols and the corresponding acetates in high enantiomeric excess (up to 99%). An effective baseline separation of the enantiomers of both substrate and product was performed in one analysis without derivatization using gas chromatography on a new chiral stationary phase (CSP) Chirasil-β-Dex containing an undecamethylene spacer (C11-Chirasil-Dex).
- Ghanem, Ashraf,Schurig, Volker
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p. 1151 - 1157
(2007/10/03)
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- Entrapment of Pseudomonas cepacia lipase with peracetylated β-cyclodextrin in sol-gel: Application to the kinetic resolution of secondary alcohols
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Co-lyophilized Pseudomonas cepacia lipase with peracetylated β-cyclodextrin was immobilized by the sol-gel process. The gel-entrapped lipase/cyclodextrin was prepared by the hydrolysis of methyltrimethoxysilane (MTMS) in the presence of the co-lyophilized lipase with peracetylated β-cyclodextrin prepared with different weight ratios (enzyme to CD). This type of enzyme preparation was subsequently used in the kinetic resolution of a set of secondary alcohols using isopropenyl acetate as an innocuous acyl donor in toluene as the organic medium. The resulting chiral alcohols (substrate) and the corresponding acetates (product) were baseline separated in one analysis without derivatization using gas chromatography on a new chiral stationary phase (CSP) Chirasil-β-Dex containing an undecamethylene spacer (C11-Chirasil-Dex).
- Ghanem, Ashraf,Schurig, Volker
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p. 2547 - 2555
(2007/10/03)
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- Aminocyclopentadienyl ruthenium chloride: Catalytic racemization and dynamic kinetic resolution of alcohols at ambient temperature
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Ruthenium-enzyme tandem catalysis: The novel racemization catalyst 1 improves the dynamic kinetic resolution (DKR) of secondary alcohols dramatically. The DKR proceeds at room temperature with isopropenyl acetate as an acyl donor. In addition, the DKR is faster even with much less lipase than in previous DKRs.
- Choi, Jun Ho,Kim, Yu Hwan,Nam, Se Hyun,Shin, Seung Tae,Kim, Mahn-Joo,Park, Jaiwook
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p. 2373 - 2376
(2007/10/03)
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- Ligand-Assisted Rate Acceleration in Transacylation by a Yttrium - Salen Complex. Demonstration of a Conceptually New Strategy for Metal-Catalyzed Kinetic Resolution of Alcohols
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(matrix presented) Yttrium-salen complexes effect transacylation between enolesters and chiral secondary alcohols, resulting in varying degrees of kinetic resolution. Even though the enantioselectivity remains modest (kfast/kslow up to 4.81), these results represent the first demonstration of a conceptually new metal-catalyzed acyl transfer process that results in kinetic resolution. On the basis of the solid-state structure of the catalyst, a novel associative mechanistic pathway is proposed for the reaction.
- Lin, Mei-Huey,RajanBabu
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p. 1607 - 1610
(2007/10/03)
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- Efficient enzymatic kinetic resolution of 4-hydroxytetralone and 3-hydroxyindanone
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Both enantiomers of 4-acetoxy- and 4-hydroxytetralone have been obtained with high enantiomeric purity by kinetic resolution using enzymes. 3-Hydroxyindanone was successfully resolved using enzymatic transesterification. The absolute configuration of the products were established by literature precedence.
- Joly,Nair, Mangalam S.
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p. 2283 - 2287
(2007/10/03)
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- Highly enantioselective aminoacylase-catalyzed transesterification of secondary alcohols
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The aminoacylase (N-acyl-L-amino acid amidohydrolase; E.C. 3.5.1.14) from Aspergillus melleus, a readily available inexpensive enzyme, catalyzes the transesterification of a wide range of chiral secondary arylalkanols with essentially absolute stereoselectivity (E> 500). Moreover, the productivities obtained with 1-phenylethanol, 1-phenylpropanol, 1-(1-naphthyl)ethanol and 1- (2-naphthyl)ethanol were substantially higher than those in the corresponding lipase-catalyzed transesterifications. (C) 2000 Elsevier Science Ltd.
- Bakker,Spruijt,Van Rantwijk,Sheldon
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p. 1801 - 1808
(2007/10/03)
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- The Photochemistry of Conformationally Rigid Benzylic Esters: 2,2-Dimethyl-1-indanyl Acetates and Pivalates
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The photochemistry, in methanol, of substituted 2,2-dimethyl-1-indanyl acetates 9a-c and pivalates 10a-c has been studied.In agreement with previous studies on benzylic esters, the results show that the substituents change the yield of products derived from the ion pair.The mechanistic conclusion reached is that the substituents change the oxidation potential of the indanyl radicals and thus the rate constant of electron transfer for converting the radical pair to the ion pair.The results also reveal two other substituent effects.First, substituents can increase the overall efficiency of the photoreaction by enhancing homolytic cleavage.The second effect is conformational.In compounds where the bond that is cleaving is conformationally mobile, such as the C-O bond in benzylic esters, substituents on the ring can change the population of the reactive conformer and thus the overall efficiency of the reaction.For the indanyl acetate esters, the difference in excited-state reaction rate between the m- and p-methoxy substituted ester is 15:1.For the m- and p-methoxy substituted benzyl acetates, this difference in reaction rate is 48:1.The larger difference in reaction rate for the conformationally mobile benzylic esters is attributed to a higher population of the unreactive conformer for the p-methoxy substituted ester.
- Pincock, J. A.,Wedge, P. J.
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p. 4067 - 4076
(2007/10/02)
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- Oxidation of Styrene Derivatives by S2O82--CuII in Acetic Acid and Acetonitrile. Reaction Paths in Oxidations via Radical Cations
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β-Aryl carbonyl compounds are major products in the oxidation of a variety of styrene derivatives by S2O82--CuII.Evidence is presented that they arise via oxidation to a radical cation, nucleophilic addition of water to give a β-hydroxyalkyl radical, CuII oxidation to epoxide, and finally acid-catalyzed rearrangement.Data on oxidation of alkyl aromatics with additional functional groups are presented.With ether and amino groups, oxidation occurs at the functional group even when it is remote from the aryl nucleus.These and previous data are summarized to give a coherent picture of the various paths by which aryl side chains may be degraded via initial radical cation intermediates.
- Walling, Cheves,El-Taliawi, Gamil M.,Amarnath, Kalyani
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p. 7573 - 7578
(2007/10/02)
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- Reaction of 1-Substituted Indenes with Diborane or N-Bromoacetamide in Protic Solvents. The Effect of the Substituent on the Stereochemistry of Addition
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The reaction of 1-substituted indenes with diborane or N-bromoacetamide (NBA) in protic solvents has been investigated to determine the effect of an increase of steric bulk of the substituent on the stereochemical course of addition.In the hydroboration reaction the proportion of the products via attack by diborane from the less hindered side increases, as the steric bulk of the substituent at C-1 increases.The reaction with NBA in aqueous dioxan, followed by acetylation, gave a mixture of 3-substituted-1-acetoxy-2-bromoindans with trans, trans and trans,cis-configuration: 1-phenylindene gave mainly trans, trans-1-acetoxy-2-bromo-3-phenylindan, while trans,cis-1-acetoxy-2-bromo-3-methylindan was the maior product in the case of 1-methylindene.
- Miura, Masahiro,Yoshida, Masaya,Nojima, Masatomo,Kusabayashi, Shigekazu
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