Process for synthesis of daidzein based on Friedel-Crafts reaction

Daidzein was synthesized from 1,3-dimethoxybenzene and p-methoxyphenylacetic acid using a process containing chlorination,Friedel-Crafts acylation,demethylation,cyclization and demethylation.Because of methyl protection,reactivity of hydroxy groups was reduced and the yield of Friedel-Crafts reaction reached to 93.6%.Hydrobromic acid(40%)was used as demethylation reagent,and all methyl in 4′,7-dimethoxyisoflavone molecule could be removed.The effect of process parameters such as catalyst amount,reaction temperature and molar ratio of materials were studied,and their optimal values were as follows:(1)in Friedel-Crafts reaction,the ratio of catalyst(aluminum chloride)and 1,3-dimethoxybenzene 1.1∶1,reaction temperature 25℃,(2)in demethylation,the ratio of demethylation reagent(aluminum chloride)and 2,4,4′-trimethoxydeoxybenzoin 1.1∶1,(3)in cyclization reaction,the ratio of triethyl orthoformate and 2-hydroxy-4,4′-dimethoxydeoxybenzoin 2∶1,reaction temperature 135℃,(4)in demethylation reaction of 4′,7-dimethoxyisoflavone,reaction temperature 122℃.The structure of product was characterized by 1H NMR and MS.