The synthesis of N-substituted isothiazol-3(2H)-ones from N-substituted 3-benzoylpropionamides

N-Substituted isothiazol-3(2H)-ones can be easily prepared from N-substituted 3-benzoylpropionamides in two experimentally simple steps, in satisfactory overall yields. Reaction of the amides with excess thionyl chloride results in the formation of N-substituted 5-benzoylisotfiiazol-3(2H)-ones, which are readily debenzoylated with alkali to the corresponding N-substituted isothiazol-3(2H)-ones. This method has now been successfully applied to the synthesis of isothiazolones N-substituted with a bulky alkyl group, such as the tert-butyl group, and with a phenyl group bearing either a strong electron-withdrawing substituent, such as the 3-nitrophenyl and 4-nitrophenyl group, or an electron-releasing substituent, such as the 4-methylphenyl and 4-methoxyphenyl group.