General procedure for the synthesis of p-neopentanoyloxybenzenesulfonyl chloride from p-pivaloyl chloride and sodium 4-hydroxybenzenesulfonate: sodium 4-hydroxybenzenesulfonate (3) (1.0 g, 0.0049 mol) was dissolved in dichloromethane (DCM) (6 ml), triethylamine (TEA) (1.0 g, 0.0098 mol) was added, and p-neopentanoyl chloride was added slowly dropwise at 20 °C (0.84 g, 0.0069 mol). After the drop was completed, the reaction mixture was magnetically stirred at 20-25°C for about 5 minutes. Subsequently, the mixture was continued to be stirred at 20-25 °C for 2 h, during which the progress of the reaction was monitored by HPLC. Upon completion of the reaction, N,N-dimethylformamide (DMF) (0.11 g, 0.0015 mol) was added and thionyl chloride (0.77 g, 0.0064 mol) was added slowly and dropwise over 15 min at 20-25 °C. Stirring was continued at this temperature for 2 h and the reaction was monitored by HPLC. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure, toluene (10 ml) was added to dissolve the residue, the salts were removed by filtration, and the filtrate was concentrated under reduced pressure. To the concentrated residue was added n-hexane (5 ml), cooled to 0 °C, the resulting suspension was filtered and the product was washed with n-hexane to give 1.1 g of light yellow solid in 81.1% yield.
