| 摘要 |
PURPOSE:To obtain the titled compound in high yield, without causing polycondensation of the product, by using phthalic acid having halogen or sulfonic acid substituent group at the 4-position as the raw material, carrying out the alkali fusion and acidification of the material, and dehydrating the crystallized product by heating in the presence of an organic solvent inert to the product. CONSTITUTION:Phthalic acid having halogen or sulfonic acid substituent group at the 4-position is used as a raw material, and is fused with a caustic alkali to substitute the halogen or sulfonic acid group. The product is acidified, and the crystallized crude 4-hydroxyphthalic acid is dehydrated by heating in an inert organic solvent such as alkylbenzene, diphenyl ether, dimethylacetamide, etc., or preferably the crude 4-hydroxyphthalic acid is extracted with the first inert oganic solvent, the solvent is removed, the second inert organic solvent is added to the extract, and the product is dehydrated by heating in the presence of the solvent to obtain the titled compoud.
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