General procedure for the synthesis of benzothiophene sulfone from benzothiophene: 0.15 g (0.0011 mol) of benzothiophene (BT) was placed in a 25 mL round-bottomed flask which was pre-filled with a mixture of 10 mL of toluene/hexane (1:4, v/v) and 0.015 g (0.0135 mmol) of oxidation catalyst. The reaction mixture was heated to 40°C in an oil bath with continuous stirring at 500 rpm. Subsequently, tert-butyl hydroperoxide was added to the reaction system at a molar ratio of oxidizer to substrate of 6.8. The oxidation reaction was carried out under continuous stirring for 6 hours. Upon completion of the reaction, the resulting white benzothiophene sulfone (BTO2) precipitate was collected by filtration and washed with hexane to remove unreacted benzothiophene. The yield was 81%. The 1H NMR (δ, ppm, DMSO-d6) data of the product were as follows: δ 7.83 (d, J = 7.2 Hz, 1H), 7.69 (t, J = 7.4 Hz, 1H), 7.62 (t, J = 9.1 Hz, 3H), 7.34 (d, J = 6.8 Hz, 1H). Elemental analysis results (calculated/measured values, %): C, 57.81/57.49; H, 3.64/3.89; S, 19.29/19.02.
