General procedure for the synthesis of 3,3-bis-(4-hydroxy-3,6-dimethylphenyl)-1-(3H)-isobenzofuranone from 2,5-dimethylphenol and phthalic anhydride: a mixture of 2,5-dimethylphenol (0.133 mol), phthalic anhydride (0.074 mol), reaction medium (0.416 mol) and Lewis acid (0.029 mol ) were placed in a reaction flask, stirred and heated at 90 °C for 5 hours. Upon completion of the reaction, the reaction mixture was cooled to room temperature and subsequently slowly poured into an ice-water mixture to induce precipitation of the product. The precipitate was collected by filtration and washed with plenty of water to remove impurities. The crude product was dried and recrystallized from methanol to afford pure 3,3-bis-(4-hydroxy-3,6-dimethylphenyl)-1-(3H)-isobenzofuranone as light yellow crystals in 85% yield. The product was analyzed by IR (KBr) showing that the characteristic absorption peaks were located at 3393 cm^-1 (O-H stretching vibration), 1729 cm^-1 (C=O stretching vibration), and 1611 cm^-1 (C=C stretching vibration of the aromatic ring).The 1H-NMR (DMSO-d6) spectrum showed the following: δ 9.40 (s, 2H, 2×OH), 1.95 (s, 12H, 4 × CH3), 6.59-6.63 (m, 4H, aromatic protons), 7.46-7.91 (m, 4H, aromatic protons) ppm. mass spectrometry analysis showed the molecular ion peak m/z 374 (M+).
