22876-20-6

3621-82-7

General procedure for the synthesis of 2,6-dichlorobenzoxazole from 6-chlorobenzo[d]oxazole-2(3H)-thione: In a 500-mL four-neck reaction flask, 50 g (0.27 mol) of 6-chlorobenzo[d]oxazole-2(3H)-thione, 300 mL of toluene, and 40 g (0.135 mol) of tris(trichloromethyl)carbonate were added. The reaction mixture was slowly warmed to 50°C and the temperature was continued at a rate of 0.5°C/min, holding the temperature for 10 minutes after each 10°C increase. When the temperature reached 105°C, the reaction was maintained for 1 hour. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure (the initial vacuum was maintained at -0.07 MPa, and when the temperature was raised to 100°C-110°C, the vacuum was increased to -0.095 MPa to completely evaporate the solvent). After evaporation, the residue was removed while hot and cooled and crystallized to give 50.82 g of 2,6-dichlorobenzoxazole with a product purity of 98.1% and a molar yield of 98.4%.