An aromatization reaction was found when 18--methyl--estra--4(5),9(10)--dien--3, 17--dione(6) was treated with triethyl orthoforrnate in dioxane in thepresence of catalytic amount of p--toluenesulfonic acid (TsOH), and 18--methyl--9(11)--dehydroestrone--3--ethyl ether (8) was obtained in 70% yield. The mechanism wasfound to be a process of etherification--oxidation reaction.
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