Copper-catalyzed aerobic asymmetric cross-dehydrogenative coupling of C(sp3)–H bonds driven by visible light†
Asymmetric cross-dehydrogenative coupling (CDC) of C(sp3)–H bonds shows great potential for rapid and stereoselective construction of C–C bonds and use of molecular oxygen as the oxidant for such transformations is appealing in the context of green synthetic methodologies. However, the poor reactivity of oxygen at the ground state and the challenges in controlling the stereochemistry make it extremely difficult to access highly enantioselective aerobic CDC reactions of C(sp3)–H precursors. Herein we report our effort towards this goal via copper-based asymmetric photocatalysis. A chiral-copper catalyst initiates the visible-light-driven oxidative CDC reaction by molecular oxygen, and governs the stereochemistry. In this way, a diastereo- and enantioselective cross-dehydrogenative coupling between carbonyl compounds and xanthene derivatives has been achieved. This work provides an economic and manageable approach to stereoselective C–C bond formation, and demonstrates a potential application of chiral copper catalysts in difficult asymmetric photochemical reactions.