Theoretical study of the reaction mechanism between triphenylphosphine with dialkyl acetylenedicarboxylates in the presence of benzotriazole

In this research, the mechanism of the reaction between triphenylphosphine R1 and dialkyl acetylenedicarboxylate R2 was investigated in the presence of NH-acid, such as benzotriazole R3 based on the quantum mechanical calculations. Theoretical studies performed for evaluation of the potential energy surfaces of all structures participated in the reaction mechanism. All structures were optimized at the B3LYP/6-311+ + g(d,p) levels. The first step of the reaction was recognized as a rate-determining step in the reaction mechanism. To check the effect of solvent on the potential energy surfaces, condensed phase calculations in dichloroethane were carried out with the polarizable continuum model. To check the effect of the structure of reactant on the potential energy surfaces, the reaction mechanism was examined in the presence of dimethyl acetylenedicarboxylate R2-M and di-tert-butylacetylenedicarboxylate R2-T. Finally, the natural bond orbital method was applied for a better understanding of molecular interaction.