Stereoselective anionic cyclizations to pyrroldines

Abstract

Cyclization of α-amino-organolithiums onto unactivated alkenes results in the formation of 2,4-disubstituted pyrrolidines with high selectivities in favour of the cis isomers. The use of the α-methylbenzyl chiral auxiliary on the nitrogen atom gives rise to 3-substituted pyrrolidines with up to 58% d.e. Without the chiral auxiliary, enantioselectivities in the presence of (-)-sparteine are poor.