Hydrochloric Acid → Acetaldehyde, 2-(4-bromo-2-methylphenoxy)-

A 5N HCl (15 mL) solution is added to a stirred solution of 4-bromo-1-(2,2-dimethoxy-ethoxy)-2-methyl-benzene (1.40 g, 5.09 mmol) in Et2O (25 mL). The two-layered solution is stirred vigorously at ambient temperature under nitrogen for 2 days. Et2O (50 mL) and saturated aqueous NaCl solution (25 mL) are added to the mixture. The organic layer is separated, washed with a half-saturated aqueous NaCl solution (30 mL) containing saturated NaHCO3 (0.5 mL), dried over MgSO4, filtered and concentrated at ambient temperature to give 1.36 g of the crude (4-bromo-2-methyl-phenoxy)acetaldehyde as oil. The oil is diluted in Et2O to form a stock solution (67 mg/mL), which is used for the subsequent reaction.