Mechanisms and Reactivity Differences for Cycloaddition of Anhydride to Alkyne Catalyzed by Palladium and Nickel Catalysts: Insight from Density Functional Calculations

Mechanisms and reactivity differences for the cycloaddition of anhydride to alkyne catalyzed by the palladium and nickel catalysts have been investigated by extensive density functional theory (DFT) calculations. The predicted free energy profiles for the Pd- and Ni-catalyzed reactions have been used to evaluate possible mechanisms for the formation of different products. Calculations show that the formation of isocoumarin via the decarbonylative addition of anhydride to alkyne is kinetically more favorable than the channel to indenone in the Ni-catalyzed reaction. On the contrary, the preparation of naphthalene through sequential liberation of CO2 and CO is kinetically more favorable than that the formation of indenone in the Pd-catalyzed process. The bonding differences between PdC and NiC bonds, arising from the relativistic effect of late transition metals, play an important role in regulating their catalytic activity. The calculation results show good agreement with the experiments.