Palladium-catalyzed dicarbonylation of 1,3-butadiene with bidentate phosphine ligands: A density functional theory study

Abstract

DFT calculations have been performed to discover the mechanism for the synthesis of dimethyl adipate (DMA) by 1,3-butadiene (BD) dicarbonylation catalyzed by a complex consisting of palladium and a bidentate diphosphine ligand. The computational results indicate that BD dicarbonylation involves two catalytic stages with the same reaction mechanism including terminal alkenyl insertion, CO migratory insertion, and methanolysis. Four different reaction routes have been explored, the pathway yielding linear DMA has the lowest alkenyl C–H insertion barrier with an overall barrier of 13.4 kcal·mol^–1 (1 kcal·mol^–1 = 4.184 kJ·mol^–1). The regioselectivity of the BD dicarbonylation depends mainly on the barrier of the alkenyl insertion into the palladium-hydrogen complex site. The computations well reproduced the experimentally observed linear selectivity.