Copper-catalyzed Aromatic C-H Activation Of C-N/O Coupling Reaction

A copper-catalyzed aromatic C-H bond activation for the formation of C~N/C-O bonds has been developed. We found the best conditions for the catalytic CNformation are cheap CuOAc as a catalyst under an oxygen as the terminal oxidant inthe presence of mixed toluene and o-dichlorobenzene, Under these conditions, theamidation reaction of aromatic C-H bonds can be successfully performed. Eitherelectron-rich or electron-poor groups on aryl rings gave the corresponding productswith high eiffciency. For the mechanistic studies, radical additives experiments wereconducted and indicated that some radical inhibitors such as BHT,1,4-dinitrobenzenedidn’t affect on these reations. As a result, we ruted out the possibility of radicalpathways for Cu-catalyzed C-H amidation. In addition, KIE expeirments show the C-H bond activation step is rate-determining step of the reaction.Intertesingly, we found little improvement of reaction conditions to be applicablefor the aromatic C-H etherification with alcohol as a coupling pater. In this system,cheap copper salt，green and environmentally friendly oxygen as oxidant, andcatalytic amount of benzoic acid as a additive without adding other excess oxidantwere the optimal conditions for C-O formation. Under these conditions,a wide rangeof electron-rich and electron-poor substrated3-methyl-2-phenyl pyridine all providedthe products in good yields. The primary alcohols and secondary alcohols are alsoperformed well in this system.