theoretical investigation of the kukhtin-ramirez reaction leading to oxyphosphoranes using dft

The kinetics and proposed mechanisms of kukhtin ramizer's reaction between trimethyl phosphite and two dicarbonyl compounds (diacetyl and benzil) were investigated using computational methods. three pos-sible mechanistic pathways were considered: a concerted cycloaddition mechanism (a), and two stepwise mechanisms (b and c), initiated by the nucleophilic attack of the phosphite on the carbon and oxygen at-oms of the carbonyl group, respectively. all calculations were per-formed using density functional theory (dft) at the m06-2x/6-31+g(d,p) level in the gas phase and in two solvents: acetonitrile and 1,4-dioxane. conformational analysis showed two stable forms (trans and gauche) for diacetyl, while only a single twisted conformation was observed for benzil. global reactivity indices indicated that trimethyl phosphite acts as a nucleophile and the dicarbonyl compounds as elec-trophiles. thermodynamic and kinetic parameters were calculated for all steps of the reaction, as well as for the overall process. in the pres-ence of diacetyl, mechanism (a) was preferred in the gas phase, while mechanism (b) became favorable in both solvents. similarly, for benzil, mechanism (a) was more favorable in the gas phase, and mechanism (b) was preferred in solution. these findings provide a deeper understand-ing of the reaction pathways and the influence of molecular structure and solvent effects on kukhtin ramizer's reaction.