Reaction Route and Mechanism of the Direct N-Alkylation of Sulfonamides on Acidic Mesoporous Zeolite β-Catalyst

Abstract

Development of highly active heterogeneous catalysts with strong acidity and mesoporous structure is a highly attractive strategy for organic synthesis. In this study, a mesoporous zeolite beta (HBeta-M) with bulky particle size and strong acidity was synthesized and used in the direct N-alkylation of sulfonamides with alcohols. The strongly acidic HBeta-M had a higher intrinsic activity with initial turnover frequency of 11 × 10–2 s–1 than those of H-form mordenite nanosheets (3.3 × 10–2 s–1) and montmorillonite (4.0 × 10–2 s–1) catalysts. The experiment and characterization results demonstrate that there are two parallel reaction routes on the acidic catalysts. One route is the reaction of benzhydrol with p-toluenesulfonamide (route I). Another route is the reaction of dibenzhydryl ether, arising from route I, with p-toluenesulfonamide (route II), which is found in this work. The reaction rate of route I (13 × 10–3 mol kg–1 s–1) was higher than that of route II (9.8 × 10–3 mol kg–1 s–1) on HBeta-M, but ...