Cyclization via carbolithiation of alpha-amino alkyllithium reagents

We report a new route to tertiary alpha-amino stereocenters by sequential alkylation of alpha-amino nitriles followed by reductive lithiation of the nitrile and cyclization onto an alkene. Reductive lithiation of alpha-amino nitriles using lithium 4,4'-di-tert-butylbiphenylide (LiDBB) and subsequent intramolecular carbolithiation proceeded with modest to high diastereoselectivity to deliver cyclic or spirocyclic ring systems. The stereoselectivity of these intramolecular carbolithiations was examined using density function calculations to evaluate plausible transition state models.