Catalytic Mechanism for the Ruthenium-Complex-Catalyzed
Synthesis of Amides from Alcohols and Amines: A DFT Study
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Abstract
Details
of the reaction mechanism for the Ru–PNN pincer complex catalyzed
amidation from an alcohol and an amine proposed by Milstein et al.
was elucidated using M06 density functional theory calculations. In
addition, the bifunctional double hydrogen transfer (BDHT) mechanism
for the dehydrogenative oxidation step was investigated for comparison.
Finally, the BDHT mechanism was found to be preferred over the β-H
elimination pathway that was proposed by Milstein et al. On the basis
of the analysis of NBO charges and orbital interactions of intermediates
and transition states, we designed a new catalyst with the addition
of an electron-donating substituent (−NEt<sub>2</sub>), which
provided much reduced energy barriers and a lower potential energy
surface along both mechanisms
