Theoretical studies on the mechanism of palladium(II)-catalysed ortho-carboxylation of acetanilide with CO

Abstract

The mechanism of palladium(II)-catalysed carboxylation of acetanilide with CO has been investigated using density functional theory calculation done at the B3LYP/6-31G(d, p)(SDD for Pd) level of theory. Solvent effects on these reactions have been explored by calculation that included a polarizable continuum model (PCM) for the solvent. Two plausible pathways which led to the formation of anhydride or benzoxazinone intermediate structure were proposed. Our calculated results suggested that the steps of forming the anhydride or benzoxazinone intermediate became the rate-determining one in the whole catalytic cycle. The process of forming benzoxazinone is more favoured kinetically with a barrier of 16.6 kcal/mol versus 22.9 kcal/mol for the pathway of forming anhydride structure. Subsequent hydrolysis process of these intermediates then provide the corresponding product ortho-acetaminobenzoic acid. The computational results are consistent with the experimental observations of Yu et al. for palladium(II)-catalysed synthesis of acetanilide based on carbon monoxide. The mechanism of the palladium(II)-catalysed carboxylation of acetanilide with CO has been investigated using DFT calculation. The reaction lead to the formation of anhydride or benzoxazinone intermediate structure proposed through two plausible pathways. The computational results are consistent with the experimental observations.