Cobalt-Catalyzed Regioselective Ortho C(sp2)-H Bond Nitration of Aromatics Through Proton-Coupled Electron Transfer (PCET) Assistance.

A cobalt-catalyzed proton-coupled electron transfer (PCET) mediated regioselective ortho-specific nitration of aromatic C(sp(2))-H bonds using chelation-assisted removable vicinal diamine directing groups was developed. The reaction proceeded under mild conditions in the presence of Co(OAc)(2)center dot 4H(2)O as the catalyst with AgNO2 utilized as the nitro source as well as terminal oxidant in the presence of O-2 as an external oxidant. No external base or additives were required for this process. Controlled experiments and mechanistic investigations with DFT calculations revealed that the reaction proceeds through a PCET promoted nitro functional group transfer pathway. Moreover, the produced compounds are valuable and pharmaceutically quite relevant.