COMPUTATIONAL STUDIES OF THE AMMONOLYSIS FOR N-METHYL β-SULTAM

Abstract

As a first step toward the understanding of the aminolysis reaction of β-sultam compounds, the ammonolysis and the effect of a second ammonia on the ammonolysis reactions of N -methyl β-sultam have been studied using Density Functional Theory (DFT) method at the B3LYP/6-31G* level. The exploration of the reaction processes proposed two different mechanisms: concerted and stepwise mechanisms. There is one pathway in concerted mechanism and two pathways in stepwise mechanisms: pathways a and b. The calculations of reaction energy barriers show that the nonconcerted route is the more favored one. Solvent effects were assessed by the PCM method. The results show that the pathway a in channel II is the most favorable in both cases. The presence of solvent disfavors the reaction, and the participation of ammonia in the ammonolysis reaction plays a positive role and reduces the active energy greatly. All transition states in the assisted ammonolysis are 45–65 kJ/mol lower than those for the non-assisted reaction. The results also show that the ammonolysis reaction have a higher energy barrier than the alcoholysis reaction. This low reactivity of amines is also observed in the reactions of N -benzoyl β-sultam and p-nitrophenyl toluene-p-sulfonate where there is a distinct preference towards oxygen nucleophiles.