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0 °C

Bromoacetyl bromide (16.14 g) was added dropwise at 0° C. under nitrogen to a stirred mixture of anhydrous aluminium chloride (21.36 g) and dichloromethane (200 ml), then the mixture was stirred at 0° C. for 30 minutes. A solution of 4-chloro-benzo[b]thiophene (13.46 g; prepared in a manner similar to that described above) in dichloromethane (100 ml) was added dropwise, and the mixture was stirred at 0° C. for 2 hours then it was poured onto ice-water (500 ml). The product was extracted into dichloromethane (2×250 ml) and the combined extracts were washed with water (200 ml), saturated aqueous sodium hydrogencarbonate solution (2×200 ml) and saturated aqueous sodium chloride solution (200 ml), then dried (Na2SO4). The solvent was removed in vacuo to leave a brown oil, which was purified by flash chromatography over silica using a 10:1 mixture of petroleum ether (b.p. 60-80° C.) and ethyl acetate as eluant. Appropriate fractions were combined and the solvents removed in vacuo to give 2-bromo-1-(4-chlorobenzo[b]thiophen-2-yl]ethan-1-one (2.8 g) as a colourless solid which was used without further purification.

1. customprepared in a manner similar to
2. additionwas added dropwise
3. stirringthe mixture was stirred at 0° C. for 2 hours
4. additionit was poured onto ice-water (500 ml)
5. extractionThe product was extracted into dichloromethane (2×250 ml)
6. washthe combined extracts were washed with water (200 ml), saturated aqueous sodium hydrogencarbonate solution (2×200 ml) and saturated aqueous sodium chloride solution (200 ml)
7. dry with materialdried (Na2SO4)
8. customThe solvent was removed in vacuo
9. customto leave a brown oil, which
10. customwas purified by flash chromatography over silica using
11. additiona 10:1 mixture of petroleum ether (b.p. 60-80° C.) and ethyl acetate as eluant
12. customthe solvents removed in vacuo