An improved method for the large-scale preparation of 4,6-dihydroxyisophthalic acid and 2,3-dihydroxyterephthalic acid has been developed. Compared to the previous procedures, this new process requires much lower CO2 pressure of 0.3 Mpa and shorter reaction time, thus providing a convenient access for large-scale synthesis. The yield is high (93% and 65%, respectively), and the oxidation of phenol is nearly inhibited, neither decolorization nor further chromatographic purification is required.
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