Preparation
AlCl3 (4.0 g, 30 mmol) was suspended in dichloromethane (30 mL). To this mixture, a solution of 1,4- dimethoxybenzene (1.38 g, 10 mmol) and triphosgene (5.94 g, 20 mmol) in dichloromethane (30 mL) was added dropwise over a period of 30 min. The resulting mixture was stirred under reflux for 7 days. It was then poured into crushed ice/ water (50 mL) and stirred with pyridine (0.5 mL) at 0 ℃ for 10 min. The layers were separated and the aqueous phase was extracted with dichloromethane (2 ×20 mL). The combined organic layers were washed with ice-cold 0.5 m HCl (30 mL) and with ice-cold water (2×10 mL), and dried over sodium sulfate. The solvent was evaporated in vacuo and the residue was purified by chromatography on silica gel, eluting with hexane/ethyl acetate (4:1→3:1→2:1→1:1), to afford 1.23 g (60%) of 2,5-dimethoxybenzoyl chloride.
