Synthesis of 3-alkylpyrrolidines by anionic cyclization

alpha-Aminocarbanions, generated by transmetallation of aminomethylstannanes, cyclize onto an unactivated alkene to give 3-alkylpyrrolidines. The intermediate organolithium either reincorporates trimethyltin or, from the tributylstannanes, can be trapped with a variety of electrophiles. From the trimethylstannane, the cyclization can be promoted catalytically using 0.2 equivalents of methyllithium. The trimethyltin group in the product can be cleaved using eerie ammonium nitrate. Trapping the 3-lithiomethylpyrrolidine with ethylchloroformate, followed by hydrolysis provides a four step synthesis of the GABA uptake inhibitor 3-pyrrolidineacetic acid. Copyright (C) 1996 Elsevier Science Ltd