Studies on Isothiazoles. I. 3-Arylisothiazole-4-carboxylic Acids

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Preparations of 5-methyl-3-phenylisothiazole-4-carboxylic acid (Xa) and related compounds are described. 3-(Halogen-substituted phenyl)-5-methylisothiazole-4-carboxylic acids were also obtained by halogenation of 4-cyano-5-methyl-3-phenylisothiazole (VIIa), followed by hydrolysis. 5-Bromo-3-phenylisothiazole-4-carboxylic acid (XV) was prepared, and converted into the 5-methylthio derivative (XVI) which was oxidized to the corresponding sulfoxide (XVII) and sulfone (XVIII).