Mechanism of Cooperative Catalysis in a Lewis Acid Promoted Nickel-Catalyzed Dual C–H Activation Reaction

The mechanism of cooperativity offered by AlMe3 in a Ni-catalyzed dehydrogenative cycloaddition between substituted formamides and an alkyne is investigated by using DFT(SMDtoluene/M06/6-31G**) methods. The preferred pathway is identified to involve dual C–H activation, with first a higher barrier formyl C(sp 2)–H oxidative insertion followed by benzylic methyl C(sp 3)–H activation. The cooperativity is traced to be of kinetic origin as evidenced by stabilized transition states when AlMe3 is bound to the formyl group, particularly in the oxidative insertion step.