Efficient <i>N</i>‑Alkylation of\nSecondary Amines to Prepare <i>N</i>‑Butyl-1,2-benzisothiazolin-3-one\nBased on Cs Ion Effect with Cs/LTA Zeolite Catalysts

<i>N</i>-Butyl-1,2-benzisothiazolin-3-one (BBIT)\nis a\nsafe and environmentally friendly new fungicide with wide application\nprospects in the field of industrial and medical antibacterial. The\nsynthesis route of BBIT by introducing hydrocarbon groups through\nthe <i>N</i>-alkylation reaction on the nitrogen atom of\n1,2-benzisothiazolin-3-one (BIT) has been widely concerned. Herein,\na series of Cs/LTA zeolite catalysts were developed by an equal volume\nimpregnation method with different cesium metal loadings to catalyze <i>N</i>-alkylation reactions of BIT instead of stoichiometric\ninorganic bases. The physicochemical properties of both prepared Cs/LTA\ncatalysts and LTA zeolite supports were characterized by XRD, FT-IR,\nXPS, thermogravimetry (TG), N<sub>2</sub>-physisorption, and CO<sub>2</sub>-TPD, and the reaction mechanisms were discussed by DFT calculations.\nThe characterization and DFT results show that the well-dispersed\ncesium metal on the LTA zeolite is the active site of the BIT reaction.\nThe synergistic interaction of Cs<sup>+</sup> interacting with zeolite\nin the rate-control step of BIT and butyl bromide reduces the reaction\nbarrier of C–N bond construction, thus prioritizing the dehydrogenation\nstep of the product intermediate and improving the selectivity of <i>N</i>-alkylation. Compared with traditional inorganic bases,\nCs/LTA catalysts have broad industrial application prospects because\nof their higher catalytic and environmental performance.