Catalytic Aerobic Regioselective Cross-Dehydrogenative Coupling of Persistent Radicals with Catechols Using CuCl2–1,10-Phenanthroline

Aerobic cross-dehydrogenative coupling of catechols provides straightforward access to multisubstituted catechols. However, the tendency of catechols to undergo oxidation to the corresponding ortho-quinones, together with the multiple coordination modes of both species, poses challenges to regioselective transformations. Building on our previous studies on the K3[Fe(CN)6]-mediated C(6)-selective cross-dehydrogenative coupling reaction between persistent radicals and 4-substituted catechols, we report here an aerobic catalytic variant using a CuCl2–1,10-phenanthroline complex under air. Two key elements underpin this cross-dehydrogenative coupling reaction, contributing to both the high C(6) regioselectivity and suppression of undesired pathways. First, the CuCl2–1,10-phenanthroline improves the yield while preserving substrate-guided regioselective radical addition. Second, the use of air suppresses undesired oxygenation of the persistent radical, thereby improving the yield of the cross-dehydrogenative coupling adducts. The developed catalytic system allows regioselective access to a range of 4,6-disubstituted catechols bearing a quaternary carbon center.