Enantioselective synthesis of 4-substituted 2-pyrrolidinones by site-selective C-H insertion of α-methoxycarbonyl-α-diazoacetanilides catalyzed by dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate]

Site- and enantioselective intramolecular C-H insertion of alpha-methoxycarbonyl-alpha-diazoacetamides has been achieved by exploiting a p-nitrophenyl group as the N-substituent and dirhodium(ll) tetrakis[N-phthaloyl-(S)-tert-leucinate] as catalyst, leading to the formation of 4-substituted 2-pyrrolidinone derivatives of up to 82% ee. The efficiency of the present protocol has been verified well by a short-step synthesis of(R)-(-)-baclofen. (C) 1997 Elsevier Science Ltd. All rights reserved.