Deracemisation of aromatic β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330 and determination of absolute configuration by 1H NMR
摘要:
Deracemisation of aryl and substituted aryl P-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330 yields the corresponding (S)-enantiomer in >99% enantiomeric excess and good yield (up to 68%). The absolute configuration of ethyl 3-(2,4-dichlorophenyl)-3-hydroxy propanoate and ethyl 3-hydroxy-5-phenyl-pent-4-enoate as determined by H-1 NMR using MTPA chloride was found to be 'S'. The chemical shifts of the methoxy groups of the two diastereomeric MTPA esters were used as diagnostic signals to determine the absolute configuration. (c) 2005 Elsevier Ltd. All rights reserved.
Dimethylzinc-Mediated, Oxidatively Promoted Reformatsky Reaction of Ethyl Iodoacetate with Aldehydes and Ketones
作者:Pier Giorgio Cozzi、Alessandro Mignogna、Paola Vicennati
DOI:10.1002/adsc.200700572
日期:2008.5.5
A practical and general Reformatskyreaction, promoted by oxidants and mediated by dimethylzinc, is described. The reaction is fast and runs at 0 °C with aldehydes and ketones, under mild reaction conditions. Preliminary results obtained for the enantioselective version show that inexpensive chiral amino alcohols could be used in the challenging formation of enantioenriched quaternary stereogenic centers
作者:Qun Cao、Roderick T. Stark、Ian A. Fallis、Duncan L. Browne
DOI:10.1002/cssc.201900886
日期:2019.6.21
An operationally simple one‐jar one‐step mechanochemical Reformatsky reaction using in situ generated organozinc intermediates under neat grinding conditions has been developed. Notable features of this reaction protocol are that it requires no solvent, no inert gases, and no pre‐activation of the bulk zinc source. The developed process is demonstrated to have good substrate scope (39–82 % yield) and
Reformatsky Reaction in Water: Evidence for a Radical Chain Process
作者:Lothar W. Bieber、Ivani Malvestiti、Elisabeth C. Storch
DOI:10.1021/jo970827k
日期:1997.12.1
The Reformatsky reaction of 2-bromo esters and carbonyl compounds in the presence of zinc can be carried out in concentrated aqueous salt solutions without any cosolvent. The reaction of bromoacetates is greatly enhanced by catalytic amounts of benzoyl peroxide or peracids and gives satisfactory yields with aromatic aldehydes. Preparative yields comparable to those of the traditional procedure are obtained with ethyl 2-bromoisobutyrate. This ester needs no catalyst and reacts even with saturated aldehydes and aromatic ketones, although in law yields. A radical chain mechanism, initiated by electron abstraction from the organometallic Reformatsky reagent, is proposed. Two nonchain pathways, involving radicals directly produced od the metal surface, may compete, especially in the case of secondary and tertiary halides.
Lewis Acid Catalysis in Supercritical Carbon Dioxide. Use of Poly(ethylene glycol) Derivatives and Perfluoroalkylbenzenes as Surfactant Molecules Which Enable Efficient Catalysis in ScCO<sub>2</sub>
作者:Ichiro Komoto、Shū Kobayashi
DOI:10.1021/jo0353177
日期:2004.2.1
Lewis acid catalysis in supercritical carbon dioxide (CO2) was investigated. While solubility of most organic materials is low in scCO(2), poly(ethylene glycol) derivatives or perfluoroalkylbenzenes were found to work as surfactants to dissolve organic materials in scCO(2). In the presence of these molecules, Lewis acid catalyzed organic reactions such as aldol-, Mannich-, and Friedel-Crafts-type reactions proceeded smoothly in scCO(2). Formation of emulsions was observed in these reactions, and the systems were studied in detail.