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Chiral N-Heterocyclic Carbene Catalyzed Staudinger Reaction of Ketenes with Imines: Highly Enantioselective Synthesis of <i>N</i>-Boc β-Lactams

Organic Letters · 2007 · Vol. 10(2) · pp. 277–280

Yanrong Zhang✉(Chinese Academy of Sciences)Lin He(Beijing National Laboratory for Molecular Sciences)Xu Wu(Beijing National Laboratory for Molecular Sciences)Pan‐Lin Shao(Beijing National Laboratory for Molecular Sciences)Song Ye(Chinese Academy of Sciences)

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Abstract

N-heterocyclic carbenes (NHCs) were demonstrated to be efficient catalysts for the Staudinger reaction of ketenes with N-tosyl, N-benzyloxycarbonyl, or N-tert-butoxycarbonyl imines. Chiral NHC 8b, conveniently prepared from L-pyroglutamic acid, catalyzed the reactions of arylalkylketenes with a variety of N-tert-butoxycarbonyl arylimines to give the corresponding cis-beta-lactams in good yields with good diastereoselectivities and excellent enantioselectivities (up to 99% ee). Two possible catalytic pathways, initiated by the addition of NHC to ketenes or imines, were discussed.

Synthesis of β-Lactam Compounds N-Heterocyclic Carbenes in Organic and Inorganic Chemistry Asymmetric Synthesis and CatalysisChemistryStaudinger reactionCatalysisCarbeneEnantioselective synthesisPyroglutamic acidCombinatorial chemistryOrganic chemistryMedicinal chemistryStereochemistry