Esterification of Aryl and Alkyl Amides Enabled by Tailor-Made and Proposed Nickel Catalyst: Insights from Theoretical Investigation.

DFT calculations are used to address the mechanism of Ni-catalyzed esterification of aryl and alkyl amides. The insight of the tailor-made catalysts in the chemo-selectivity is addressed in this work. The reaction steps for esterification of aryl and alkyl amides catalyzed by both Ni(SIPr)2 and Ni(terpyridine)2 include: oxidative addition, metathesis, and reductive elimination processes. Ni(SIPr)2 can catalyze the esterification of aryl amides rather than Ni(terpyridine)2 due to high reaction barrier in oxidative addition process, while Ni(terpyridine)2 can catalyze the esterification of alkyl amides rather than Ni(SIPr)2 due to high reaction barrier in metathesis process. It is found that the charge distribution on Ni is different in these two complexes. An amino-substituted terpyridine Ni complex is designed to catalyze both aryl and alkyl amides through low transition-state energies because of the electron-donating ability of three amino substitutes. The results reveal that the chemo-selectivity is mainly controlled by the electron-donating ability of ligands.