作者:Merritt B. Andrus、Erik J. Hicken、Jeffrey C. Stephens
DOI:10.1021/ol0491235
日期:2004.6.1
[reaction: see text] Asymmetric surrogate glycolate alkylation has been performed under phase-transfer conditions. Diphenylmethyloxy-2,5-dimethoxyacetophenone with trifluorobenzyl cinchonidinium catalyst and cesium hydroxide provided alkylation products at -35 degrees C in high yield (80-99%) and with excellent enantioselectivities (90:10 to 95:5). Useful alpha-hydroxy products were obtained using
Cinchonine based phase-transfer catalysts were developed for enantio selective conjugate additions to electron deficient alkenes. including acylates, acrylonitrile, and chalcone. N-Trifulorobenzyl cinchoninium bromide 6 catalyst (20 mol %) in THF at -40 degrees C promoted the conjugate addition of arylketone glycolate 1 generating S-product 2 in good yields and selectivities. Catalyst, solvent, and base variations are presented along with conditions to convert the products to intermediates useful for multistep applications. (C) 2007 Published by Elsevier Ltd.