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 route II predominantly contributed
to the formation of the target product with high selectivity. Hereby,
a complete reaction mechanism is proposed in this work.
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