Stereoselective Synthesis of Highly Substituted Cyclopropanes

Significance

Cyclopropanation of highly substituted and Z-conjugated alkenes remains a significant challenge.This report describes a solution to the problem. The method is stereoselective, and the dr in the products 2a-f reflects the Z/E ratio of the starting alkene. Reaction of morpholine amides 3 with organolithiums afforded cyclo­propylketones 4 without loss of diastereoselecti­vity. The reaction is noteworthy for its simplicity, and for its chemoselectivity (only the proximal alkene reacted to 2b).