Visible-Light-Promoted Tandem Annulation of N-(o-Ethynylaryl)acrylamides with CH2Cl2

A novel tandem annulation of N-(o-ethynylaryl)acrylamides, with CH2Cl2 as a one-carbon unit, for the divergent synthesis of cyclopenta[c]quinolin-4(5H)-ones and benzo[j]phenanthridin-6(5H)-ones, which relies on the substitution effect of the 2 position of the acrylamide moiety, is described. Promoted by the visible-light photoredox catalysis, this reaction allows the formation of multiple chemical bonds through multiple C-Cl/C-H functionalizaiion and [2 + 2 + 1] annulation cascades.