Phosphorus oxychloride → 2-Chloro-5-methyl-1,3-benzoxazole

Participants

Reaction Steps

5-Methyl-benzooxazole-2-thiol (5.0 g, 30.2 mmol), phosphorus oxychloride (25.0 mL, 269.4 mmol), and phosphorus pentachloride (7.56 g, 36.3 mmol) were combined in CH2Cl2 (30 mL), and the reaction was stirred at room temperature overnight. The mixture was concentrated several times from fresh CH2Cl2 to remove traces of phosphorus oxychloride, and the residue was treated with saturated aqueous Na2CO3 to adjust to pH 8. The aqueous layer was extracted twice with CH2Cl2, and the combined organic layers were washed with H2O and brine, and then dried over Na2SO4, decanted, and concentrated. The crude material was purified by silica gel chromatography (0-100% EtOAc in hexanes) to give the title compound.

Provenance & Evidence