Methods for the preparation of substituted homoallylic amines and their conversion to pyrrolidines or pyrrolizidines are described. N-Alkylation of a variety of homoallylic secondary amines with (tributylstannyl)methyl methanesulfonate and subsequent tin-lithium exchange, generates organolithium species that undergo intramolecular carbolithiation (anionic cyclization). High stereoselectivities in the cyclization, particularly for the formation of 2,4-disubstituted pyrrolidines, are obtained.
amines - carbanions - cyclizations - lithiation - heterocycles