Visible-Light-Promoted C(sp(3))-C(sp(2)) Cross-Dehydrogenative Coupling of Tertiary Amine with Imidazopyridine

A metal-free visible-light-promoted C(sp(3))-C(sp(2)) cross-dehydrogenative coupling between tetrahydroisoquinoline and imidazo[1,2-a]pyridine has been developed to afford 3-substituted imidazopyridines using a catalytic amount of rose bengal as photosensitizer under aerobic conditions. The present methodology is also applicable to imidazo[1,2-a]pyrimidine, indolizine, indole, and pyrrole as well as N,N-dimethyl aniline. Wide substrates scope, use of organo photocatalyst, metal-free, and mild reaction conditions are the attractive features of this methodology.