Oxalyl chloride (0.8 mL) was added to a solution of 5-bromo-2-chlorobenzoic acid (2 g) in dichloromethane (20 mL) and dimethylformamide (0.2 mL) under a nitrogen atmosphere. The reaction mixture was stirred for one hour at 25° C to 30° C. After completion of the reaction, the reaction mixture was concentrated under a vacuum at 40° C to 45° C. to obtain an oily residue. The oily residue was dissolved in dichloromethane (20 mL) and cooled to 0° C. To this solution, phenol (1.1 mL) and aluminium chloride (2.3 g) were added at 0° C. to 5° C. The reaction mixture was stirred at 0° C to 5° C for 2 hours. The reaction mixture was allowed to warm to about 20° C, and triethylsilane (3.4 mL) was slowly added to it at the same temperature. The reaction mixture was stirred for about 36 hours from 20° C to 25° C. After completion of the reaction, 4-bromo-1-chloro-2-(4-ethoxybenzyl)benzene was obtained by further purification.
