Phenyltrimethylammonium bromide dibromide → 2-Bromo-2-(4-chlorophenyl)1-[1-(3,4-dichlorophenyl)cyclobutyl]ethanone

Phenyltrimethylammonium tribromide (6.59 g) was added in portions at −5° C. to a stirred solution of 2-(4-chlorophenyl)-1-[1-(3,4-dichlorophenyl)cyclobutyl]ethanone (6.2 g) in tetrahydrofuran (150 ml). The mixture was stirred at ambient temperature for 4 hours, allowed to stand at ambient temperature for a further 48 hours, then it was filtered, and the solvent removed in vacuo. The residue was purified via flash chromatography over silica using a 3:97 mixture of ethyl acetate and petroleum ether (b.p. 60-80° C.) as eluant. Appropriate fractions were combined, and the solvents removed in vacuo. The residue was triturated with petroleum ether (b.p. 60-80° C.) (30 ml) and the resulting solid was collected by filtration and dried in vacuo at ambient temperature to give 2-bromo-2-(4-chlorophenyl)1-[1-(3,4-dichlorophenyl)cyclobutyl]ethanone as a colourless solid (4.83 g), m.p. 109-110° C.