Theoretical Study of the Reaction Among Isocyanide, Dialkyl Acetylenedicarboxylate and Acetic Anhydride: The Investigation of the Reaction

In this work, stepwise reaction mechanism of the [2+3] cycloaddition reaction among alkyl isocyanides (contains tertbutyl isocyanide, cyclo hexyl isocyanide) with dialkyl acetylenedicarboxylate (contains dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate and ditertbutyl acetylenedicarboxylate) at the presence of acetic anhydride was investigated both in the gas phase and in solvent was studied theoretically. The potential energy of all structures participated in the reaction path was evaluated. The geometry of all the structures participated during the reaction path, the ratedetermining step, and potential competitive routes during the reaction coordinate were evaluated. Also, dielectric constant effect of the solvent, the effect of substituted alkyl groups on the potential energy surfaces, and the best product configuration were investigated based upon the quantum mechanical calculations. For better understanding of the molecular interaction, the natural bond orbital method (NBO) and AIM analysis were applied. The results indicated that, the first step of the reaction was recognized as ratedetermining step and the reaction rate was predicted to be dependent on the concentration of alkyl isocyanides and dialkyl acetylenedicarboxylate. It was also found that, the electron donating of different alkyl groups was not the main factor for the variation in the potential energy surfaces of the reaction; however, the steric factor of the bulky alkyl groups participating in the reaction path was found to be the main factor.