4-Bromo-7-methyl-benzo[1,2,5]thiadiazole

1457-92-7

2255-80-3

4-Methylbenzo[c][1,2,5]thiadiazole (2.7 g, 18 mmol) was used as starting material and dissolved in 17.5 mL of a solvent mixture of acetic acid and water (6:1, v/v). A solution prepared from 1 mL of bromine (19.5 mmol, 1.1 eq.) with 2 mL of acetic acid was added dropwise under stirring. The reaction mixture was first stirred at 50 °C and then warmed to 60-70 °C to continue the reaction for 5 hours. Upon completion of the reaction, water was added to the reaction mixture to precipitate the product. The precipitate was collected by filtration and washed sequentially with Na2S2O3 solution and water. Finally, purification by recrystallization from ethanol afforded 4-bromo-7-methylbenzo[c][1,2,5]thiadiazole (11) as white needle-like crystals (2.6 g, 11 mmol, 62% yield). The melting point of the product was 135-136°C. 1H-NMR (250 MHz, CDCl3): δ=7.71 (d, J=7.3 Hz, 1H), 7.23 (d, J=7.3 Hz, 1H), 2.69 (s, 3H) ppm. 13C-NMR (63 MHz, CDCl3): δ=155.27, 153.30, 132.17,131.39,128.74,111.30,77.16,17.81 ppm. mass spectrometry (EI): m/z=228[M+],230[(M+2)+],149[(M-Br)+]. Calculated elemental analysis (C7H5BrN2S): C,36.70; H,2.20; N,12.23; measured values: C,36.61; H,2.21; N,12.42.