A convenient method for 3-pyrroline synthesis.

[reaction: see text]. The synthesis of a range of 3-pyrrolines has been achieved from primary amine starting materials using a two-step alkylation/alkylidene carbene CH-insertion reaction sequence. We have shown that insertion into a range of CH-bond types is possible, and the formation of nitrogen-bearing quaternary stereocenters is a relatively facile process. The insertion reaction occurs with >95% retention of stereochemistry, but the presence of protecting groups on nitrogen is generally deleterious to the cyclization process.