Chiral organic contact ion pairs in metal-free catalytic asymmetric allylic substitutions

J Am Chem Soc. 2011 Mar 23;133(11):3732-5. doi: 10.1021/ja110213t. Epub 2011 Feb 28.

Abstract

Chiral contact ion-pair catalysis with particular focus on metal-free processes is gaining in interest. As a result, new perspectives are opened, and highly stereoselective transformations, traditionally performed under metal catalysis, can be realized. Herein, we report the development of an unprecedented asymmetric Brønsted acid-catalyzed allylic alkylation. The concept relies on chiral contact ion-pair catalysis, in which the chiral organic counteranion of an allylic carbocation induces high enantioselectivities and allows access to biologically relevant chromenes in good yields and with excellent enantioselection.