The general procedure for the synthesis of 3,4,5-trimethoxybenzoyl chloride from 3,4,5-trimethoxybenzoic acid was as follows: thionyl chloride (13.7 mL, 189 mmol) was added dropwise to a solution of CHCl3 (30 mL) containing 3,4,5-trimethoxybenzoic acid (8.00 g, 37.7 mmol). After the dropwise addition, the reaction mixture was heated to reflux and maintained for 4 hours. Upon completion of the reaction, the mixture was cooled to room temperature. Subsequently, the solvent and excess thionyl chloride were removed by distillation under reduced pressure to afford 3,4,5-trimethoxybenzoyl chloride as a colorless oil in quantitative yield. The obtained product can be used in the subsequent reaction without further purification. The characteristic absorption peaks of the infrared spectrum (NaCl) were: νmax/cm-1 2970, 2944, 1750, 1590, 1457, 1415, 1130, 1128.
