A metal-free, organophotoredox-catalyzed cross-dehydrogenative coupling reaction for synthesizing various biologically active heterocycles is reported. Diverse substrates were found to be amenable to this methodology, affording the corresponding cyclized products in good to excellent yields. In all cases, oxygen serves as a clean oxidant.

Abstract

An efficient construction of C═N and C─O bonds by the metal-free organophotoredox catalyzed intramolecular cross-dehydrogenative coupling of tertiary amines with amides, amines, and acids as nucleophiles is described. A series of 12,13-dihydro-6H-isoquinolino[2,1-a]quinazolin-6-one, 5,6-dihydrobenzo[4,5]imidazo [2,1-a]isoquinoline, and 4b,13-dihydro-6H,12H-benzo[4,5] [1,3]oxazino[2,3-a]isoquinolin-6-one derivatives were prepared in good to excellent yields. All the transformations proceeded smoothly under an oxygen atmosphere, serving as a clean oxidant. Moreover, the current approach was extended for the synthesis of the biologically active natural product, rutaecarpine.