N(OCCC(C)C)=O.[CH3:9][O:10][C:11]([C:13]1[S:17][C:16](N)=[N:15][CH:14]=1)=[O:12].C(OCC)(=O)C>O1CCOCC1>[CH3:9][O:10][C:11]([C:13]1[S:17][CH:16]=[N:15][CH:14]=1)=[O:12]The mixture of 2.15 g of isoamyl nitrite and 10 ml of dioxane was stirred at 80° C. under a nitrogen atmosphere. A solution of 1.23 g of 2-aminothiazole-5-carboxylic acid methyl ester (7-3) in 20 ml of dioxane was added drop wise. The mixture was refluxed for 2 hours. After cooling to room temperature 30 ml of ethyl acetate was added. The mixture was washed with brine and dried and the solvent evaporated under reduced pressure. The crude product is purified on silica, thus yielding 0.54 g (48%) of thiazol 5-carboxylic acid methyl ester (7-4).
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