Enantioselective Cyclopropanation of 2-Cyano-3-arylacrylates Using Carbohydrate-Based Crown Ethers

Enantioenriched, highly functionalized cyclopropane derivatives were prepared by a simple and green approach using monosaccharide-based chiral crown ethers as phase transfer catalysts. The Michael-initiated ring closure (MIRC) reactions of diethyl bromomalonate with 2-cyano-3-phenylacrylate took place with complete diastereoselectivity in the presence of chiral lariat ethers derived from carbohydrates and enantioselectivity up to 87 % ee was achieved. Among the catalysts tested, the monoaza-15-crown-5 lariat ether having a methyl beta-D-glucopyranoside unit and a 2-(3,4-dimethoxyphenyl)ethyl group on the nitrogen generated the highest asymmetric induction (87 % ee). In the reactions of analogous 2-cyano-3-arylacrylates, enantioselectivity was in the range of 8-91 % ee.