Potassium ferricyanide-mediated regioselective cross-dehydrogenative coupling of catechols with 2-oxindoles and benzofuranones

Abstract

Cross dehydrogenative coupling (CDC) reactions of catechols offer a direct route to multi-substituted catechols. While in situ oxidation to ortho-quinones has advanced CDC reactions of catechols, controlling regioselectivity remains challenging. Herein, we present details of our investigations into the C(6)-selective CDC reaction of 4-substituted catechols with the persistent radical precursors, 2-oxindoles and benzofuranones. Our optimization studies, based on mechanistic control experiments, led to the development of a cooperative oxidation system using dissolved O₂ and a sub-stoichiometric amount of K₃[Fe(CN)₆], which expands the substrate scope of the C(6)-selective CDC reaction of 4-substituted catechols.