Intramolecular Vinylation of Secondary and Tertiary Organolithiums

Deprotonation of benzylic ureas, carbamates, and thiocarbamates bearing N′-alkenyl substituents generates carbanions which undergo intramolecular migration of the alkenyl group to the carbanionic center. Solvolysis of the urea products generates α-alkenylated amines. With an enantiomerically pure starting urea, migration proceeds stereospecifically, generating in enantiomerically enriched form products containing allylic quaternary stereogenic centers bearing N. Computational and in situ IR studies suggest that the reaction, formally a nucleophilic substitution at an sp2 carbon atom, proceeds by a concerted addition-elimination pathway.