5-Ethylthiazol-2-amine was synthesized as follows: n-butyraldehyde (10.8 g, 0.15 mol) was dissolved with urea (22.8 g, 0.3 mol) in chloroform (75 mL) at 0 °C, and sulfuryl chloride (13.5 mL, 0.166 mol) was added slowly and dropwise. The reaction mixture was gradually warmed to room temperature and stirred continuously for 1 hour. Subsequently, the solvent was removed by rotary evaporation. Ethanol (200 mL) was added to the residue and heated to reflux overnight before the solvent was removed by evaporation again. The resulting residue was suspended in water (200 mL) and the precipitate was collected by vacuum filtration to give 5-ethylthiazol-2-amine (9.5 g, 40% yield) as a light brown solid. Mass spectrometry analysis showed m/z 129.1 [M + H]+.
