Acetic Anhydride → 2-Bromo-4-formamidothiazole
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C(O[C:5](=[O:7])C)(=O)C.C(OC=O)(=O)C.Br.[NH2:15][C:16]1[N:17]=[C:18]([Br:21])[S:19][CH:20]=1.C([O-])(=O)C.[Na+]>N1C=CC=CC=1.C(O)=O>[Br:21][C:18]1[S:19][CH:20]=[C:16]([NH:15][CH:5]=[O:7])[N:17]=1C(O[C:5](=[O:7])C)(=O)C.C(OC=O)(=O)C.Br.[NH2:15][C:16]1[N:17]=[C:18]([Br:21])[S:19][CH:20]=1.C([O-])(=O)C.[Na+]>N1C=CC=CC=1.C(O)=O>[Br:21][C:18]1[S:19][CH:20]=[C:16]([NH:15][CH:5]=[O:7])[N:17]=1Acetic anhydride (100 ml) was cooled to 0° C. and treated with 98% formic acid (50 ml.). The resulting mixture was heated at 50° C. for 15 minutes then cooled to 0° C. To this solution of formic-acetic anhydride was added 4-amino-2-bromothiazole hydrobromide (26 g, 0.1 m) followed dropwise by pyridine (25 ml.). The reaction mixture was allowed to stand for 1 hour at room temperature then poured onto 20% aqueous sodium acetate solution (500 ml). The resulting crystals were removed by filtration, washed once with water (100 ml) then recrystallised from ethanol to give the 2-bromo-4-formamidothiazole (12 g, 58%). m.p. 167° C. d. (Found: C, 23.55; H, 1.6; N, 13.45. C4H3N2BrOS requires C, 23.2; H, 1.45; N, 13.5%).
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