Visible light-mediated radical addition cascade cyclization of aryl isocyanides with tricarbonyls: rapid access to substituted phenanthridines and isoquinolines†

A visible light-mediated synthesis of substituted phenanthridines and isoquinolines from ortho-substituted aryl isocyanides and tricarbonyl compounds is unveiled via the radical addition cascade cyclization (RACC) strategy. This acid/base-free method involves an oxidant (a persulphate salt) and a Ru-photocatalyst. This protocol avoids the use of halogenated compounds as pre-functionalized carbonyl precursors. The products can be easily post-modified to other important small molecules. The functional group tolerance of the reaction and the yields of the products are good without any scalability issues. The mechanistic investigation suggested the presence of a radical pathway during the reaction.