The mechanism of the Hantzsch ester hydrogenation of imines catalyzed by chiral BINOL-phosphoric acid has been investigated using DFT methods. Despite the importance of this reaction, there are a number of possible detailed mechanisms, and the preferred pathway has not been firmly established. Our calculations show that the catalyst not only activates the imine group for the reaction by acting as a Brønsted acid but also establishes an interaction with the Hantzsch ester that can lead to an explanation for the enantioselectivity.

There have been many comparisons of computational methods applied to ground states, but studies of organic reactions usually require calculations on transition states, and these provide a different test of the methods. We present calculations of the geometries of nineteen covalent-bond forming transition states using HF and twelve different functionals, including GGA, hybrid-GGA and hybrid meta-GGA approaches. For the calculation of the TS geometries, the results suggest that B3LYP is only slightly less accurate than newer, computationally more expensive methods, and is less sensitive to choice of integration grid. We conclude that the use of B3LYP and related functionals is still appropriate for many studies of organic reaction mechanisms.

Triazabicyclodecene (TBD) has recently been shown to be an effective organocatalyst for the ring-opening polymerization (ROP) of cyclic esters. Using DFT methods, we have studied possible mechanisms of this reaction. Our studies explain not only the narrow polydispersity index (PDI) observed in the ROP of six-membered ring lactones, but also the surprising failure of the ROP for the more reactive butyrolactone.

BINOL-phosphoric acid catalysts have been used successfully in many reactions involving imines. In this paper, we present a model, based on DFT calculations, for describing the degree and sense of the enantioselectivity of these reactions that is able to predict the correct enantioselectivity for the reactions in more than 40 recent publications. We rationalize the different factors on which the enantioselectivity depends, focusing on the E- or Z-preference of the transition structures and the orientation of the catalyst with respect to the electrophile.