Improved One-pot Synthesis of 4,6-Dihydroxyisophthalic Acid and 2,3-Dihydroxyterephthalic Acid

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.