TEMPO-Mediated Direct C(sp)-H Alkoxylation/Aryloxylation of 1,4-Quinones.

A convenient and efficient transition-metal-free method has been developed for the C(sp)-H alkoxylation/aryloxylation of 1,4-quinones by direct cross-dehydrogenative coupling with readily available alcohols and phenols in the presence of TEMPO under simple and mild conditions. The method allowed the installation of a wide range of alkoxy/aryloxy groups, exhibited high functional group tolerance, showed a broad substrate scope, afforded good to excellent yields of products in a simple one-pot operation, and could be performed on a gram scale. Mechanistic investigation indicated the involvement of the radical pathway.