536-25-4

67-56-1

1571-72-8

536-25-4

1. 3-Amino-4-hydroxybenzoic acid (0.40 g, 2.61 mmol) was dissolved in anhydrous methanol (10 mL), and trimethylsilyl chloride (TMSCl, 0.75 mL, 5.94 mmol) was added. 2. The reaction mixture was stirred at 55°C for 48 h. 3. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure. 4. The crude product was purified by silica gel column chromatography. The crude product was purified by silica gel column chromatography using ethyl acetate as eluent to afford methyl 3-amino-4-hydroxybenzoate (0.25 g, 1.50 mmol, 57% yield) as a white solid. 5. Methyl 3-amino-4-hydroxybenzoate (0.20 g) was dissolved in anhydrous tetrahydrofuran (THF, 10 mL), and methyl 3-amino-4-hydroxybenzoate was added to methyl 3-amino-4-hydroxybenzoate, 0.26 g, 1.5 mL, and methyl 3-amino-4-hydroxybenzoate, 0.20 g, 2.5 mL, 2.4 mL, 2.5 mL. (0.26 g, 1.46 mmol). 6. The reaction mixture was stirred at room temperature overnight. 7. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure. 8. The residue was treated with water (15 mL) and extracted with ethyl acetate (3 × 15 mL). 9. The organic layers were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. 10. The crude product was recrystallized from ethanol to give 2-thioalkylbenzo[d ]oxazole-5-carboxylic acid methyl ester (21, 0.22 g, 1.05 mmol, 88% yield) as a brown solid with a melting point of 203-205°C. The crude product was extracted with ethanol.