Visible-light-induced cyclization of 2-alkenyl-1,1' - biphenyls

A novel and efficient method for the preparation of phenanthrene-9,9(10H)-dicarbonitrile derivatives has been developed, which occurs through the cyclization of 2-malononitrilemethylene-substituted 1,1'-biphenyls under metal-free conditions. The transformation involves photoelectrocyclization via visiblelight mediated energy transfer catalysis and [1,5]-H shift, and the protocol has a range of advantages, including simplicity and mildness of the reaction conditions, environmental friendliness, good functional-group tolerance, and excellent yields of products.