Pyridinolysis of Carbonyl and Phosphoryl Transfer: A DFT Study

초록

The pyridinolysis (XC5H4N) of phenoxy carbonyl isothiocyanate (Z=C) and phenoxy hydrogen isothiocyanophosphonate (Z=PH) (Scheme 1) are investigated using DFT method. Kinetic and thermodynamic parameters as well as molecular orbital overlapping indicate the back-side nucleophilic attack of pyridines and leaving group departure are preferable strategies. The C=O system was studied in the gas and in solution, whereas the P=O system studied only in acetonitrile solution. According to the literature1-2 and several experimental evidences, three mechanisms are possible: concerted or a stepwise or both from the intermediate or transition state. In this study, we found SN2 type concerted nucleophilic attack for the both cases found to be more favorable over equatorial (frontal) attack for the P=O system. In addition, the steric effects of the ligands play important decisive role for the rate determining step change in the course of reactions.