Stereoselective synthesis of 4-alkylidene pyrrolidinones and pyrrolizidinones

alpha-Aminoalkylcuprates prepared from tert-butoxycarbonyl protected amines undergo a conjugate addition reaction with alpha,beta-beta,gamma-allenyl e sters to afford the corresponding beta,gamma-unsaturated esters with a high degree of stereoselectivity. Treatment of the unsaturated esters with PhOH /TMSCl or catechol boron bromide effects amine deprotection and lactamizati on to afford a 4-alkylidene-2-pyrrolidinone ring with preservation of the o riginal olefin stereochemistry. The method can be used to prepare 4-alkylid ene 2-pyrrolidinones and 2-pyrrolizidinones (C) 1999 Elsevier Science Ltd. All rights reserved.