2-Acetylfuran → 4-(Furan-2-yl)-1,3-thiazol-2-amine

2-Acetylfuran (5.10 g, 46.0 mmol) was dissolved in a mixed solvent of dichloromethane (50 mL) and methanol (50 mL), and N,N,N,N-tetra-n-butylammonium tribromide (22.3 g, 46.0 mmol) added thereto, then the solution was stirred at room temperature for 1 hour. The reaction mixture was concentrated under reduced pressure, and water was added to the resulting residue, then the mixture was extracted with ethyl acetate. The organic layer was washed with brine and dried over anhydrous magnesium sulfate. The solvent was then evaporated under reduced pressure. The resulting residue was dissolved in acetonitrile (60 mL), and thiourea (3.5 g, 46.0 mmol) added thereto, then the solution was stirred at room temperature for 30 minutes. The precipitated solid was collected by filtration, and to the resulting solid was added saturated sodium bicarbonate aqueous solution and ethyl acetate added, then the mixture was extracted. The organic layer was washed with brine and dried over anhydrous magnesium sulfate. The solvent was then evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate=3:1) to give 2-amino-4-(2-furyl)thiazole (1.53 g, 20%).