Abstract:

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.

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