Emodin was synthesized by demethylation of physcion.Three catalysts of demethylation,AlCl3,H2SO4 and HBr,were compared.

• 目的与方法将大黄素甲醚脱甲基制备大黄素,对以三氯化铝、浓硫酸、氢溴酸作为催化剂的3种方法进行比较。