Synthesis and reactions of 2-amino-5-carbomethoxy-6-phenyl-6H-1,3,4-thiadiazine
Treatment of methyl 3-phenyl-3-chloro-2-oxopropionate with thiosemicarbazide gives 2-amino-S-carbomethozy6-phenyl-6H-1,3,4-thiadiazine, theisomeric 2-hydrazino-4-carbomethoxy-S-phenylthiazole, orthecorresponding carboxylic acids depending on the acidity of the medium. The intermediate on the way to the thiadiazine proved to be a covalent 4,5-hydrate. These reactions are subject to thermodynamic control. Acetylation of the above thiadiazine occurs either with retention of the thiadiazine structure or via sulfur atom extrusion to give acetylated 3-amino-4-phenyl-5-carbomethoxypyrazole.