66490-33-3

23967-57-9

66490-33-3

General procedure for the synthesis of 4-chlorobenzo[b]thiophene from 4-chlorobenzo[b]thiophene-2-carboxylic acid: a mixture of 2-carboxy-4-chlorobenzo[b]thiophene (50.00 g), 1,3-dimethyl-2-imidazolidinone (DMI; 200 ml) and 1,8-diazabicyclo[5.4.0]undec-7-ene (140.7 ml) was prepared by heating and stirring a mixture of 1,8-diazabicyclo[5.4.0]undec-7-ene (140.7 ml) at 160- 195 °C for 6 hours with heating and stirring. After completion of the reaction, the mixture was cooled to 10°C and then slowly added to 3N hydrochloric acid (350 ml) pre-cooled to 10°C. The reaction mixture was extracted with toluene (500 ml) followed by washing the toluene layer sequentially with 3N hydrochloric acid, water, aqueous sodium bicarbonate solution, water, brine and water. After completion of washing, the toluene layer was concentrated to give 4-chlorobenzo[b]thiophene. Yield: 36.78 g. NMR hydrogen spectrum (DMSO-d6) data were as follows: δ 7.38 (1H, t, J = 8.4 Hz), 7.51 (1H, dd, J = 5.5,0.8 Hz), 7.48 (1H, dd, J = 7.7,0.9 Hz), 7.94 (1H, dd, J = 5.5,0.4 Hz), 8.02 (1H. dt, J = 8.0,0.9Hz).