Key mechanistic features of the Ni-dcype catalyzed C–H/C–O coupling of benzoxazole and naphthalen-2-yl pivalate were studied. Special attention was devoted to the base effect in the C–O oxidative addition and C–H activation steps, as well as the C–H substrate effect in the C–H activation step. No base effect in the C(aryl)–O oxidative addition to Ni-dcype was found. However, the nature of the base plays a crucial role in the C–H activation/nickelation step. Addition of Cs2CO3 base to the reaction mixture of the C–O oxidative addition product Ni(dcype)(Naph)(PivO), 1B, and azole, forms the Ni(dcype)(Naph)[PivOCs·CsCO3] cluster complex rather than undergoing PivO– ® CsCO3– ligand exchange. Coordination of azole to the resulting cluster complex forms intermediate with a weak Cs-N(azole) bond, the existence of which increases acidity of the activated C–H bond and reduces C–H activation barrier. This emerging mechanistic knowledge was validated by further exploring base and C–H substrate effects via replacing Cs2CO3 with K2CO3 and benzoxazole with 1H-benzo[d]imidazole or quinazoline. Based on these findings we proposed the modified catalytic cycle for the Ni(cod)(dcype)-catalyzed C–H/C–O biaryl coupling of benzoxazole and naphthalen-2-yl pivalate

Key mechanistic features of Ni-catalyzed C-H/C-O biaryl coupling of azoles and naphthalen-2-yl pivalates

249th National Meeting (2015)

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