Asymmetric synthesis of pyrroloindolones by N-heterocyclic carbene catalyzed [2+3] annulation of α-chloroaldehydes with nitrovinylindoles

Angew Chem Int Ed Engl. 2013 Dec 16;52(51):13562-6. doi: 10.1002/anie.201305957. Epub 2013 Nov 4.

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.

Keywords: N-heterocyclic carbenes; annulation; asymmetric synthesis; indole derivatives; organocatalysis.