Asymmetric Synthesis of Pyrroloindolones by N‐Heterocyclic Carbene Catalyzed [2+3] Annulation of α‐Chloroaldehydes with Nitrovinylindoles

Abstract

NHC-enolate plus 3: N-heterocyclic carbenes (NHCs) serve as organocatalysts for the [2+3] annulation of nitrovinylindoles with α-chloroaldehydes via an intermediate azolium enolate. The method provides trans-disubstituted pyrroloindolones with good yields and excellent diastereo- and enantioselectivities. Further transformations lead to tetracyclic pyrrolo[1,2-a]indoles with potential psychotropic and other bioactivities.