Method for preparing 1-oxo-1,3-dihydro-3-hydroxybenzofuran-5-formic acid

The invention discloses a method for preparing 1-oxo-1,3-dihydro-3-hydroxybenzofuran-5-formic acid. The method disclosed by the invention comprises the following steps: dissolving 2,5-toluene dihalideinto a tetrahydrofuran solution, carrying out a reaction with magnesium metal under iodine catalysis so as to obtain a corresponding Grignard reagent, and introducing carbon dioxide so as to obtain 2-methylterephthalic acid; performing chromium trioxide oxidation and diluted hydrochloric acid hydrolysis on the 2-methylterephthalic acid in the presence of glacial acetic acid, acetic anhydride andconcentrated sulfuric acid so as to prepare the 1-oxo-1,3-dihydro-3-hydroxybenzofuran-5-formic acid. The preparation method disclosed by the invention is simple in synthesis, cheap and readily available in raw material and convenient for large-scale preparation, reaction treatment in the invention is simple, and a pure target product can be obtained by virtue of washing, extracting and filtering only. Moreover, requirement