Isothiazole-4-sulfonic acid

Isothiazole-carbo dic acids, 112,118 Isothiazole-sulfonic acid, 112... 

Isothiazoles.1 These heterocycles can be prepared by reaction of a-acetylenic aldehydes or ketones with hydroxylamine-O-sulfonic acid and then with sodium hydrosulfide in a buffered aqueous solution. 

Alternatively, treatment of thioenaminones 296 with hydroxylamine-O-sulfonic acid gives the isothiazoles 297 in good yields, Scheme 82 (80JOC4857). 

Isothiazole is also sulfonated by oleum to yield the 4-sulfonic acid derivative in both thiazole and isothiazole the orientation of sulfonation is in agreement with the calculated r-electron density patterns of the parent heterocycles. ... 

Alkyl-5-acetamidoisothiazoles are nitrosated at the 4-position by nitrosylsulfuric acid (78JOC4154). Isothiazoles are sulfonated at the 4-position using either oleum or sulfur trioxide <72AHQ14)1). 

Thiete structures have been suggested as fragmentation products in the mass spectra of a thietane fused to a 3-lactam, an ortho disulfide of a thiolbenzoate ester, -propanethiol, thiirane carboxylic acid esters, isothiazoles, thiazoles, 1,3-dithiole 2-thiones, 1,3-dithiolene-2-ones, S-ethyl thio-benzoate, and thianaphthene sulfones. Tetramethylthiete may have been formed on thermolysis of the p-toluenesulfonyl-hydrazone of 2,2,4,4-tetramethyl-3-thietanone. " Thiete 2-thione may be an intermediate in the decomposition of 1,2-ditholium salts by the action of bases. " 2,2-Diphenyl-2H-thiete is suggested as an intermediate in the reaction of diphenyldiazomethane with 1,2,3-benzo-thiadiazole which yields 9-phenylthioxanthene and three other products. ... 

Electrophilic sulfonation of isoxazole is of no preparative value the substitution of only the phenyl-substituent of 5-phenylisoxazole with chlorosulfonic acid makes the same point. Both isothiazole and pyrazole can be satisfactorily sulfonated at C-4. 

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