m-Chloroperbenzoic acid → 2-Amino-5-(3-pyridylsulfinyl)thiazole

To a mixture of 2-amino-5-(3-pyridylthio)thiazole (3.0 g) in a mixture of dichloromethane (100 ml) and chloroform (100 ml) was added dropwise the solution of 3-chloroperbenzoic acid (3.4 g) in dichloromethane (50 ml) at 5° C. with stirring. The mixture was stirred at 5° C. for 3 hours. The reaction mixture was washed with aqueous sodium bicarbonate and the aqueous layer was extracted with a mixture of tetrahydrofuran and ethyl acetate (1:1), washed with aqueous saturated sodium chloride and dried over magnesium sulfate. The solvent was concentrated under reduced pressure and the residue was recrystallized from ethanol to give 2-amino-5-(3-pyridylsulfinyl)thiazole (1.2 g, yield: 37.2%). mp: 178°-179° C.