Dual-Catalysed Intermolecular Reductive Coupling of Dienes and Ketones

We report a mild, catalytic method for the intermolecular reductive coupling of feedstock dienes and styrenes with ketones. Our conditions allow concomitant formation of a cobalt hydride species and single-electron-reduction of ketones. Subsequent selective hydrogen-atom-transfer from the cobalt hydride generates an allylic radical which can selectively couple with the persistent radical-anion of the ketone. This radical-radical coupling negates unfavourable steric interactions of ionic pathways and avoids the unstable alkoxy radical of previous radical olefin-carbonyl couplings which were limited, as a result, to aldehydes. Applications of this novel and straightforward approach include the efficient synthesis of drug-molecules, key-intermediates in drug synthesis and site-selective late-stage functionalisation.