Enantioselective cyclopropanation of conjugated cyanosulfones using carbohydrate-based crown ether catalysts

A few new D-galactose- and D-glucose-based monoaza-15-crown-5 type lariat ethers have been synthesized. These macrocycles and their derivatives proved to be efficient catalysts in the cyclopropanation of (E)-3-phenyl-2-(phenylsulfonyl)acrylonitrile performed with diethyl bromomalonate under mild phase transfer conditions. Among the catalysts tested, the macrocycle having methyl alpha-D-galactopyranoside unit generated the highest asymmetric induction (80% ee). In the reactions of the arylsubstituted phenylsulfonyl-acrylonitrile derivatives, the cyclopropanation of the meta- and parasubstituted starting materials took place with high ee values (75-84% ee). The cyclopropane derivatives synthesized from analogous alpha,beta-unsaturated cyanosulfones containing naphthyl, pyridyl, furyl and thienyl groups were obtained with enantioselectivities up to 85%, and in excellent yields. (C) 2020 The Authors. Published by Elsevier Ltd.