Palladium-Catalyzed Regioselective Synthesis of 1-Hydroxycarbazoles Under Aerobic Conditions

A palladium-catalyzed aerobic C-H amidation of N-Ts-2-amino-3 '-hydroxylbiaryls has been developed to afford a diverse range of 1-hydroxycarbazoles with high regioselectivity and efficiency. This protocol benefits from operational simplicity, robustness, and sustainability with the use of ambient air as the sole terminal oxidant. Further elaboration of the products obtained from this process provides facile access to various carbazole alkaloids including carbazolequinones and biscarbazoles. A mechanism involving dual directing group-assisted regioselective C-H activation at the more sterically hindered C2 '-position of 2-amino-3 '-hydroxylbiaryls is proposed.