Reaction route and mechanism of the direct N-alkylation of sulfonamides on acidic mesoporous zeolite Beta catalyst

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 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 Route-II predomin...