Stereoselective synthesis of 4-alkylidene pyrrolidinones and pyrrolizidinones
摘要:
alpha-Aminoalkylcuprates prepared from tert-butoxycarbonyl protected amines undergo a conjugate addition reaction with alpha,beta-beta,gamma-allenyl esters 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 lactamization to afford a 4-alkylidene-2-pyrrolidinone ring with preservation of the original olefin stereochemistry. The method can be used to prepare 4-alkylidene 2-pyrrolidinones and 2-pyrrolizidinones (C) 1999 Elsevier Science Ltd. All rights reserved.