Organocatalytic Asymmetric Synthesis of trans-γ-Lactams

Abstract

An N-heterocyclic carbene (NHC)-catalyzed highly diastereo- and enantioselective formal [3+2] reaction of o-hydroxy aromatic aldimines and cinnamaldehydes for the preparation of enantioenriched trans-γ-lactams was developed. An internal hydrogen bond between the o-hydroxy and the imine function was crucial for the reactivity and chemical selectivity. Trans-γ-lactam 3 d was easily oxidized to multifunctional 1,4-benzoquinone 8, which could further be transformed to biaryl 9 in the presence of a phosphoric acid. Finally, preliminary results for a kinetic resolution of (±)-trans-γ-lactam 3 d under asymmetric NHC catalysis are reported.

Keywords: N-heterocyclic carbene; asymmetric synthesis; kinetic resolution; o-hydroxy aromatic aldimines; trans-γ-lactams.