Quantum chemical research of structures and some transformations of phthalimido-substituted keto-stabilized sulfur ylides

The behavior and structure of molecules of phthalimido-substituted keto-stabilized sulfur ylides have been investigated by means of ab initio (RHF/6-31G(d,p), MP2(fc)/6-31G(d,p), MP2/6-31G(d,p), MP2(fc)/6-31+G(d,p), MP2/6-31+G(d,p) and B3LYP/6-31G(d,p)) methods of quantum chemistry. The influence of the structure of ylides on their reactivity has been researched on the basis of a novel reaction of intramolecular cyclization. The results of the analysis of conformers indicate that the presence of the alkyl substituent at the β-position leads to a diminution of the distance between interacting functional groups. The comparison of the found values of Gibbs free energies in some possible reactions of ylides calculated at various temperatures leads to the conclusion that the higher temperature, the greater the thermodynamic preference of the cyclization reaction. The influence of the temperature on the formation of linear by-products is significantly lower. From the point of view of thermodynamic preference, it is improbable for the Wittig and Corey-Chaykovsky reactions to be the most characteristic for ylides.