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.