Sustainable C-H activation approach for palladium-catalyzed, regioselective functionalization of 1-methyl-3-phenyl quinoxaline-2(1H)-ones in water.

A sustainable and environment-friendly approach for the regioselective acylation of 1-methyl-3-phenyl quinoxaline-2(1H)-ones has been developed in water. The present protocol requires palladium acetate as a catalyst and exhibits a wide substrate scope by employing commercially available, non-toxic aldehydes, benzyl alcohols and toluenes as acyl surrogates. The mechanistic studies demonstrated the adoption of a free radical pathway for this transformation. Furthermore, the established protocol exhibits excellent regioselectivity and high functional group tolerance and is amenable to the gram scale. The established synthetic method also provides a practical and convenient route for the late-stage functionalization of some potential drug candidates.