Asymmetric Activation of tropos 2,2′‐Biphenol with Cinchonine Generates an Effective Catalyst for the Asymmetric Strecker Reaction of N‐Tosyl‐Protected Aldimines and Ketoimines

Tropo' bello! Asymmetric activation of tropos biphenol 1 and Ti(OiPr)4 with cinchonine 2 generates a remarkably effective catalyst in situ for the asymmetric Strecker reaction of N-tosyl (Ts) imines under mild conditions. Various substrates including aldimines, aryl alkyl ketoimines, and unsymmetrical diaryl ketoimines were investigated, and most of them exhibited high enantioselectivities (up to 99 % ee) as well as high reactivities.