Amide-Directed Catalytic Asymmetric Hydroboration of Trisubstituted Alkenes
作者:Sean M. Smith、James M. Takacs
DOI:10.1021/ja908257x
日期:2010.2.17
rhodium-catalyzed reaction is stereospecific. In addition, simple TADDOL-derived phenyl monophosphite ligands in combination with Rh(nbd)(2)BF(4) afford highly enantioselective catalysts (seven examples, 91-98% ee). These catalysts provide an alternative methodology to prepare Felkin or anti-Felkin acetate-aldol products and related derivatives that are obtainable from the intermediate chiral organoboranes
METHOD FOR THE PRODUCTION OF OPTICALLY ACTIVE ALPHA ALKYL CARBONYL COMPOUNDS
申请人:Breit Bernhard
公开号:US20100305352A1
公开(公告)日:2010-12-02
A method for the production of optically active α-alkylcarbonyl compounds with retention of the stereo information of the starting compound. The starting compound used here is a carbonyl compound which has, in the α-position, a leaving group which is substituted by an alkyl group with inversion of the configuration. The substitution of the leaving group is effected with the use of an alkylmagnesium Grignard and a zinc (II) salt or a zinc organyl. The method permits the production of optically active α-alkylcarbonyl compounds at very mild temperatures (for example 0° C.) with the use of starting compounds which are easy to prepare and economical and nontoxic catalysts, it also being possible to achieve a very high yield.
The perfluoroalkylation of lithium enolates of chiral N-acyloxazolidinones with perfluoroalkyl iodides mediated by triethylborane proceeds with good diastereomeric excess (55%–93% de).
Triethylborane-mediated reactions of lithium enolates derived from chiral N-acyloxazolidinones with ethyl difluoroiodoacetate allows easy access to α-(ethoxycarbonyl)difluoromethylated carboximides with good diastereomeric excess (86->98%de). The stereochemistry of the (ethyoxycarbonyl)difluoromethylated carboximides indicates that the (ethoxycarbonyl)difluoromethyl radical generated from ethyl difluoroiodoacetate and triethylborane reacts preferentially on the si face of the lithium enolates.
The introduction of an EtO2CCF2- group into lithium enolates of chiral N-acyloxazolidinones with ethyl difluoroiodoacetate mediated by triethylborane proceeds with good diastereomeric excess (86->98% de).