Chemoselective reduction of ketones: trifluoromethylketones versus methylketones
摘要:
Treatment of an equimolar mixture of trifluoromethylketones (TFMKs) and methylketones (MKs) with Et2Zn resulted in selective reduction of the TFMKs in good yield. In contrast, treatment of an equimolar mixture of TFMKs and MKs with NaBH4 in the presence of CeCl3 in EtOH/H2O (10:1) at -10degreesC reduced only the MKs. (C) 2005 Elsevier Ltd. All rights reserved.
design of sequential and concurrent cascades was investigated. The proper selection of the enzymes permits the synthesis of amino alcohol stereoisomers in high to excellent yields (86–>99% conversion) and remarkable stereocontrol (up to >99% de and >99% ee) using an aqueous medium and mild reaction conditions.
The modular cyanoalkylamination of alkenes using bench-stable and easy-to-handle α-imino-oxy acid oxime esters as difunctional reagents creates new synthetic avenues. A metal-free photosensitization protocol for the installation of both amino and cyanoalkyl functionalities onto alkene feedstocks in a single step via twodifferently reactive nitrogen-centered radicals was developed via energy-transfer
Chemo- and Enantioselective Routes to Chiral Fluorinated Hydroxyketones Using Ketoreductases
作者:Brendan T. Grau、Paul N. Devine、Lisa N. DiMichele、Birgit Kosjek
DOI:10.1021/ol701810v
日期:2007.11.1
ee (>98%) and yield by a chemo- and stereoselective reduction of prochiral methyl/trifluoromethyl diketones using commercially available ketoreductase enzymes. By using p- and m-trifluoroacetyl substituted acetophenones, we demonstrate that ketoreductases can selectively differentiate between methyl and trifluoromethyl ketones within the same molecule. As a result, useful catalysts were identified that
Treatment of an equimolar mixture of trifluoromethylketones (TFMKs) and methylketones (MKs) with Et2Zn resulted in selective reduction of the TFMKs in good yield. In contrast, treatment of an equimolar mixture of TFMKs and MKs with NaBH4 in the presence of CeCl3 in EtOH/H2O (10:1) at -10degreesC reduced only the MKs. (C) 2005 Elsevier Ltd. All rights reserved.