Enantioselective electrochemical cobalt-catalyzed aryl C–H activation reactions

Abstract

Enantioselective redox transformations typically rely on costly transition metals as catalysts and often stoichiometric amounts of chemical redox agents as well. Electrocatalysis represents a more sustainable alternative, in particular through the use of the hydrogen evolution reaction (HER) in place of a chemical oxidant. In this work, we describe strategies for HER-coupled enantioselective aryl carbon-hydrogen bond (C–H) activation reactions using cobalt in place of a precious metal catalyst for the asymmetric oxidation. Thus, highly enantioselective carbon-hydrogen and nitrogen-hydrogen (C–H and N–H) annulations of carboxylic amides were achieved, which gave access to point and axially chiral compounds. Furthermore, the cobalt-mediated electrocatalysis enabled the preparation of various phosphorus (P)–stereogenic compounds by selective desymmetrization through dehydrogenative C–H activation reactions.

An electric cobalt C–H clipper Electrochemical oxidation is an environmentally friendly means of modifying carbon–hydrogen (C–H) bonds in the synthesis of complex molecules. However, selecting just one of two mirror-image products generally requires a soluble co-catalyst, very often a precious metal. von Münchow et al . report that the more Earth-abundant cobalt is also a viable co-catalyst for electrochemical C–H oxidations of aryl rings. They showcase the method for a wide variety of products with chiral carbon and phosphorus centers, as well as axially chiral polycyclic compounds. —JSY

Electrooxidative cobalt-catalyzed C–H activation selectively produces C-stereogenic, P-stereogenic, and atropisomeric compounds.