from first principles PP-I-1

PP-I-3Mechanism Investigation of the NHC-Catalyzed Benzoin Condensation ofAldehydesBunev A.S. 1 , Statsyuk V.E. 2 , Ostapenko G.I. 21 D. Mendeleyev University of Chemical Techology of Russia, Moscow, Russia2 Togliatti State University, Togliatti, Russiaa.s.bunev@gmail.comA computational study with the B3LYP and PBE density functional theory was carried out tostudy the reactions mechanism for the benzoin condensation for aldehydes catalyzedby N-heterocyclic carbenes. We used benzaldehyde and NHC(1-4) carbenes as a simplifiedquantum-chemical model substrate and explored the detailed mechanism to achieve a clearerunderstanding of the catalytic processes (Scheme 1).Scheme 1. Mechanism for the benzoin condensationThe calculations presented in this work were carry out in the framework of density functionaltheory (DFT) using the B3LYP and PBEPBE functional as implemented in Gaussian 03 suiteof programs. The full geometry optimization of all minima and transition states involved wasperformed at the chosen level of theory. Frequency calculations were carried out at the samelevel of theory to identify all of the stationary points as minima (zero imaginary frequencies)or first-order saddle points (one imaginary frequency) and free energies at 298.15 K tocalculate, which include entropic contributions by taking into account the vibrational,rotational, and translational motions of the species under consideration.118