Phosphahelicenes in asymmetric organocatalysis: [3+2] cyclizations of γ-substituted allenes and electron-poor olefins

Article abstract of DOI:10.1002/anie.201500299

The first use of phosphahelicene in enantioselective organocatalysis is reported. New chiral phosphahelicenes have been prepared and enable highly enantioselective [3+2] cyclization reactions between arylidene- or alkylidenemalononitriles and γ-substituted allenoates or cyanoallenes. These reactions afford cyclopentene derivatives in both high yields and diastereoselectivities, with enantiomeric excesses of up to 97 %.