The Role of N- Substitution in Regio- and Stereoselective Vinylogous Imidonaphthoquinone (VINAquinone) [2 + 2] Photocycloadditions.

Described in this manuscript are intramolecular [2 + 2] photocycloadditions of readily available vinylogous imidonaphthoquinones whose regio- and diastereoselectivity is dependent on the substitution on the vinylogous imide. When exposed to 419 nm light, 2° vinylogous imidonaphthoquinones give novel bridged tetracyclic aza-anthraquinones from a rare crossed [2 + 2] cycloaddition reaction. In contrast, exposure of the corresponding 3° substrates to white light leads to linear adducts. Also outlined here are auxiliary controlled diastereoselective reactions and cyclobutane fragmentations as a means of generating the spirofused γ-lactam moiety present in the ansalactam family of natural product.