3-Bromo-2-methyl-benzo[b]thiophene

1195-14-8

10243-15-9

General procedure for the synthesis of 3-bromo-2-methyl-benzo[b]thiophene from 2-methylbenzothiophene: A solution of bromine (Br2, 2.10 mL, 6.55 g, 41.5 mmol, 1.02 eq.) in chloroform (CHCl3, 60 mL) was added slowly and dropwise over a period of 5 hr. to a solution of 2-methylbenzothiophene (5, 6.00 g, 40.8 mmol. 1.00 equiv) solution in chloroform (CHCl3, 300 mL). The reaction mixture was stirred at room temperature for 15 hours. Upon completion of the reaction, the reaction was quenched with saturated aqueous sodium sulfite (Na2SO3) (50 mL) and extracted with dichloromethane (CH2Cl2, 4 x 100 mL). The combined organic layers were washed with saturated aqueous sodium bicarbonate (NaHCO3) and then dried with anhydrous sodium sulfate (Na2SO4) (2 × 100 mL). The solvent was removed by distillation under reduced pressure and the product was purified by fast column chromatography (silica gel, hexane as eluent) to afford 3-bromo-2-methyl-benzo[b]thiophene (6) as a colorless solid in 96% yield (8.68 g, 38.2 mmol). Thin layer chromatography (TLC, silica gel plate, hexane as unfolding agent): rf = 0.25. 1H NMR (400 MHz, DMSO-d6): δ = 8.00-7.94 (m, 1H), 7.68-7.63 (m, 1H), 7.51-7.38 (m, 2H), 2.54 (s, 3H) ppm. 13C NMR (101 MHz. DMSO-d6): δ = 137.62, 136.57, 135.65, 125.38, 125.14, 122.75, 121.92, 105.78, 15.17 ppm. mass spectrometry (EI): m/z [M]+ of C9H7BrS Calculated value: 225.9448; measured value: 225.9446.