9.2 g of dibenzothiophene was placed in a 500 mL three-necked round-bottomed flask and 150 mL of dichloroethane was added. The dibenzothiophene was dissolved under magnetic stirring and the temperature of the reaction system was adjusted to 10 °C. To the reaction system, 10.7 g of N-bromosuccinimide and 3 g of acidic clay (pH 3, measured as a 10% aqueous solution) were sequentially added for 6 hours. The amount of acidic clay was 32.6 wt% of the mass of dibenzothiophene. Upon completion of the reaction, 150 mL of 5% aqueous sodium bicarbonate was added to the reaction mixture, stirred for 1 h and left to stratify. The organic phase was washed twice with water, followed by spinning to remove all solvents to give the crude product as a solid.HPLC analysis (254 nm wavelength) showed 96.71 wt% of 2-bromodibenzothiophene in the crude product, 2.21 wt% of the by-product 2,7-dibromodibenzothiophene, and 0.01 wt% of unreacted dibenzothiophene. The crude product was dissolved in 300 mL of acetonitrile and heated to 82 °C to dissolve it completely. After slow cooling to 30 °C, the precipitated 2,7-dibromodibenzothiophene by-product was removed by filtration. The filtrate was vortexed to 310 mL and cooled to room temperature to precipitate a solid. The solid was collected by filtration to give 12.3 g of 2-bromodibenzothiophene in 93.18% yield and ≥99% purity.
