Photoinduced Copper-Catalyzed Carbocyclization of 1,7-Enynes with Sulfonium Salts via Radical Relay Strategy

A visible-light-induced copper-catalyzed sulfonium salts ring-opening radical-triggered tandem cyclization of 1,7-enynes for the synthesis of three types of highly valuable (distal thioethers-containing) heteropolycyclic compounds is described. Preliminary mechanistic studies suggest that the construction of three C-C bonds and a tetracycle in one pot is based on 6-exo-dig cyclization/1,5-hydrogen-atom transfer/5-endo-trig cyclization radical relay processes under mild conditions. The reaction selectivity shifted to the 6-exo-dig cyclization (rather than 1,5-hydrogen-atom transfer) in the presence of a benzyl group at the 2-position of the acrylamide moiety, enabling the successful synthesis of a diverse range of benzo[j]phenanthridin-6(5H)-one derivatives. Meanwhile, this approach provides a new route to complex cyclopenta[c]quinolin-4-ones derivatives.