Cp*Ir(III)-Catalyzed Mild and Broad C−H Arylation of Arenes and Alkenes with Aryldiazonium Salts Leading to the External Oxidant-Free Approach

Reported
herein is the development of Cp*Ir­(III)-catalyzed direct C−H
arylation of arenes and alkenes using aryldiazonium tetrafluoroborates,
the use of which as an aryl precursor and also as an oxidant via C−N2 bond cleavage was a key to success in achieving a mild and
external oxidant-free procedure. Mechanistic experiments and DFT calculations
revealed the turnover-limiting step to be closely related to the formation
of an Ir­(V)-aryl intermediate rather than the presupposed C−H
cleavage. Under the developed mild arylation conditions, a wide range
of benzamides were smoothly arylated. In addition, synthetic utility
of the current C−H arylation procedure was also demonstrated
successfully for the (Z)-selective arylation of enamides
and C8-selective reaction of quinoline N-oxides.