2-Aminothiazole → 1,3-Thiazol-2-ylthiourea

To a solution of 2-aminothiazole (630 mg, 6.29 mmol) in acetone (30 mL) was slowly added benzoyl isothiocyanate (845 μL, 6.29 mmol) at room temperature. The reaction mixture was heated to a gentle reflux for 6.5 h, at which time it was cooled to room temperature and concentrated in vacuo. The residue was added acetonitrile (50 mL) and the yellow precipitate was filtered. The filtrate was concentrated in vacuo and the residue was taken up in 10% aqueous sodium hydroxide (50 mL). The heterogeneous reaction mixture was heated to a gentle reflux for 1 h then cooled to room temperature and stirred for 16 h. To the reaction mixture was added 6 N hydrochloric acid until pH reached 7. To the aqueous layer was added ammonium hydroxide (50 mL) followed by ethyl acetate then separated. The organic layer was washed with brine then dried over anhydrous magnesium sulfate, filtered and the filtrate concentrated in vacuo to afford N-1,3-thiazol-2-ylthiourea (717 mg, 71%) as a pale yellow powder. The powder was then taken up in chloroform (50 mL) and to this suspension was added iodomethane (281 μL, 4.50 mmol). The reaction mixture was heated to reflux for 2 h, at which time it was cooled to room temperature and concentrated in vacuo. The residue was purified by column chromatography (SiO2, hexanes/ethyl acetate) to afford methyl N-1,3-thiazol-2-ylimidothiocarbamate (200 mg, 26%). MS (EI) for C5H7N3S2: 174 (MH+).