Traceless Redox-Annulations of Alicyclic Amines

Abstract

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox­-neutral annulations with ortho -(nitromethyl)benzaldehyde. Benzoic­ acid acts as a promoter in these reactions, which involve concurrent amine α-C-H bond and N-H bond functionalization. Subsequent removal of the nitro group provides access to tetrahydroprotoberberines not accessible via typical redox-annulations. Also reported are decarboxylative annulations of ortho -(nitromethyl)benzaldehyde with proline and pipecolic acid.