A DFT Study of an Organocatalytic Enantioselective Mannich Reaction Under the Sway of Noncovalent Interactions

Abstract

Density functional theory (DFT) calculations were performed for an asymmetric Mannich reaction between iminophosphorane and malononitrile catalyzed by a multifunctional organocatalyst. A quantum chemical modeling of the CC bond-forming reaction coordinate, proton transfer reaction coordinate, and torsional reaction coordinate was investigated with the help of M06-2X DFT calculations with a def2-SVP basis set. It was found that the rate-determining and enantiodetermining step (transition state) was neither associated with the CC bond-forming reaction coordinate nor with the proton transfer coordinate. The enantiodetermining step was associated with the torsional degrees of freedom and influenced by the network of non-covalent interactions.