| 摘要 |
An improved synthesis of diphenylethers, and in particular, the bacteriostat 2,4,4'-trichloro-2'-hydroxydiphenylether, is described wherein 2'-acetyl-2,4,4'-trichlorodiphenylether is oxidised under Baeyer-Villiger conditions to produce 2'-acetoxy-2,4,4'-trichlorodiphenylether in near quantitative yield. Best oxidative conditions include the use of anhydrous permaleic acid produced in situ. The ester is purified readily by simple recrystallization, as no dibenzofurans and only minor amounts of byproducts are formed in the process. The ester is converted into the desired halogenated phenolic diphenylether, 2,4,4'-trichloro-2'-hydroxydiphenylether, by hydrolysis or transesterification. The final product is purified to a high degree by vacuum distillation and crystallization to meet current purity standards for approved applications.
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