The general procedure for the synthesis of 5-hydroxy-2-methylbenzoxazole from the compound (CAS: 24558-42-7) was as follows: compound 2 (20.0 g, 119.7 mmol) was dissolved in N,N-dimethylformamide (DMF, 300 mL) and the solution was cooled to 0 °C. Phosphorus oxychloride (POCl3, 20 g, 131.6 mmol) was slowly added dropwise while keeping the internal temperature below 10 °C. After the dropwise addition, the reaction mixture was continued to be stirred at 0°C for 1 hour. After completion of the reaction, water (1 L) was added to the reaction mixture and extracted with ethyl acetate (EA, 300 mL x 3). The organic phases were combined and concentrated. The concentrated residue was dissolved in methyl tert-butyl ether (MTBE, 800 mL) and washed with deionized water (200 mL × 3). The organic layer was dried with anhydrous sodium sulfate (Na2SO4), filtered and concentrated. Finally, the residue was washed with a solvent mixture of dichloromethane (DCM) and petroleum ether (PE) (4:1, 250 mL, v/v) to afford compound 3 (13.5 g, 75.6% yield).
