Energy transfer-driven regioselective synthesis of functionalized phenanthridines by visible-light Ir photocatalysis

Abstract

A photocatalytic strategy for regioselective synthesis of phenanthridine derivatives from N-(2-arylbenzylidenamino)pyridinium salts has been developed. Utilization of an Ir photocatalyst, [Ir{dF(CF₃)ppy}₂(dtbbpy)]PF₆ (dF(CF₃)ppy = 3,5-difluoro-2-(5-(trifluoromethyl)-2-pyridyl)phenyl, dtbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), is a key to successful reactions. The excited Ir catalyst does not serve as a 1e-redox reagent but as an energy donor toward the pyridinium salts. The present system can be also applied to one-pot synthesis of Trisphaeridine, an anti-cancer drug.