Abstract
Heterogeneous catalytic N-alkylation has increasingly been recognized as a sustainable approach for the formation of C-N bonds, particularly in the synthesis of high-value nitrogen compounds. Based on the characteristic that calcined hydrotalcites exhibit basic sites of varying strengths depending on their Mg/Al molar ratios, this study employed Mg-Al layered double hydroxides (LDHs) as precursors to synthesize a series of layered double oxides (LDOs) with different Mg/Al ratios via high-temperature topotactic transformation. These LDOs were then used as solid base catalysts to investigate the mechanistic influence of basic site strength on the N-alkylation of 1,2-benzisothiazolin-3-one (BIT) for the selective synthesis of N-butyl-1,2-benzisothiazolin-3-one (BBIT). Notably, Mg(4)Al(1)O-600 showcased superior catalytic activity, achieving a BIT conversion rate of 61.66% and a BBIT yield of 42.81% within 20 h. A structure-property correlation analysis suggests that the abundant medium-strength basic sites function as active centers for selective N-alkylation, thereby significantly improving selectivity toward BBIT. The predominant catalytic mechanism is identified as an S(N)2 nucleophilic substitution. Additionally, kinetic analysis indicates that the reaction is largely influenced by the coupled mass transfer and reaction behavior of BIT.