Mameli, Efisio published the artcilePyrolysis of ammonium saccharin and of ammonium thiosaccharin. Saccharinimine and pseudosaccharinamine, Product Details of C7H6N2O2S, the publication is Gazzetta Chimica Italiana (1940), 855-74, database is CAplus.
The work is a continuation of that on the comparative behavior of saccharin (I) and thiosaccharin (II) (cf. M.-M., C. A. 29, 3998.8). Various modifications of the Defournel method of preparing NH4 saccharin (III) were tried, including temperature, concentration, and proportion of reagents. At 170°, III loses its crystallinity; at 210° it softens and evolves NH3; at 222° it melts; at 233-5° the evolution of NH3 increases and a brown liquid is formed; at 240-60° NH3 is no longer evolved, and a yellow-brown, vitreous mass remains. The latter, extracted with Et2O (to remove I), then with water, the aqueous extract evaporated, the residue extracted with Et2O, and purified from boiling water, yields 33% of 0-C6H4(CONH2)SO2ONH4 (IV), m. 257-60° (cf. various m. ps., e. g., Ber. 22, 759 (1889); Am. Chem. J. 18, 825(1896); 30, 370(1903)). After the Et2O and water extractions, a solid substance remains, which, purified by boiling water, yields 50% of C6H4.SO2.NH.C:NH (V), m. 315°. NH4 thiosaccharin (VI) was prepared by a method already described (cf. M.-M., C. A. 10, 1174) and by new methods (II and (NH4)2CO3, II and urea, II and thiourea, etc.), which will be published later. At 170°, VI evolves NH3, H2S and unidentified vapors; at 225°, evolution of gases is more intense; at 224-50° the mass reddens; at 285° the residue softens and contracts; at 295-300° it melts to a dark liquid, and evolves H2S. Elimination of H2S is usually complete at 270°. The residue, extracted with Et2O and then with water, as before, does not yield IV. The final residue is V. To compare V with the supposedly identical compound already known, it was prepared by 8 methods: (1) pyrolysis of III; (2) pyrolysis of VI; (3) heating I and (NH4)2CO3 at 250°; (4) heating II and (NH4)2CO3 at 300°; (5) heating I and urea at 250°; (6) heating II and urea at 150°; (7) action of NH3 on chloropseudosaccharin, and (8) pyrolysis of saccharin oxime. Methods (3), (4) and (5) are new, and the details will be published later. The yield by method (1) was 50%; that by method (2) was 80-85%. The products by all methods m. 315°. An extensive study of V was carried out. Its crystalline form depends on the conditions of crystallization; but all forms m. 315° and have the same solubility and chem. properties, so the different forms are polymorphic rather than tautomeric. Aqueous solutions of V are slightly acid to litmus. It is insoluble in dilute or concentrated HCl, dilute or 60% H2SO4, aqueous alkali carbonates, and dilute NH4OH. It is soluble in 10% NaOH and KOH, slightly soluble in concentrated NH4OH and 6% aqueous alkalies. V is precipitated from its alk. solutions by acids and by CO2, whereas I and II are precipitated from their alk. solutions by acids but not by CO2. In 30% aqueous alkalies, V dissolves in part, and in part forms alkali salts, which dissolve only by dilution with water. The earlier discovery that cold aqueous alkalies hydrolyze V to I and NH3 (cf. M.-M., C. A. 29, 3998.8) was confirmed, and it was further found that when V and 5% NaOH are allowed to stand several days or are heated 2 h., o-C6H4(SO2NH2)CO2H is formed. Because of the behavior of V with aqueous alkalies, it was impossible to prepare alkali salts. When aqueous or alc. NaOH or KOH solutions of V were allowed to evaporate, I was obtained, and when alc. NH3 solutions were evaporated, V was recovered. Hot aqueous V does not reduce NH3-AgNO3, but precipitates the Ag salt, C7H5O2N2SAg, of V. The best method is to dissolve V in a min. of 10% NaOH or preferably NH4OH, and precipitate by excess AgNO3 solution The fact that V is less acidic than I is shown also by their behavior toward 5KBr-KBrO3 mixtures and 5KI-KIO3 mixtures I liberates Br and I; V liberates neither (II gives a precipitate which was not studied). V is slightly soluble in cold AcOH, PhNH2 and C5H5N, and readily soluble in hot PhNH2, hot C5H5N, cold concentrated H2SO4 and 80% H2SO4, from all of which solutions it is precipitated unaltered by addition of water, whereas II and C5H5N react. When KNO2 is added to a solution of V in concentrated or 80% H2SO4, there is no reaction. V does not react with H2S, (NH4)2S, BzH, piperonal or PhCH:CHCHO at room temperature, or with AlCl3 or Na2SO4 at 200°. Hot aqueous V does not reduce NH3-AgNO3, but precipitates the Ag salt, C7H5O2N2SAg, of V, which is not altered by prolonged boiling of the liquid It can be prepared also by dissolving V in a min. of 10% NaOH, or preferably NH4OH, and adding excess AgNO3. The instability of alk. solutions of V made it impossible to prepare its Na and NH4 salts. V in dilute EtOH, NH2OH.HCl (4 mols.) and NaOAc (4 mols.), heated 90 min., yields saccharin oxime, m. 208-10° (cf. M.-M., C. A. 27, 2682). The results in general point to the constitution of V as C6H4.SO2.NH.C:NH, rather than C6H4.SO2.N:CNH2, i. e., pseudosaccharinamine, which was supposed to have the constitution of the probably identical compound, m. 315°, prepared otherwise by Jesurum (Ber. 26, 2294, 2298(1893)) and by others. In the same way, the iminoamide of saccharincarboxylic acid, prepared by Zincke and Greune (C. A. 16, 2322) should have the constitution: H2NCOC6H3.SO2.NH.C:NH, rather than H2NCOC6H3.SO2.N:CNH2. The transformation of III and of VI as described has few precedents, either with respect to the formation of IV or of V; in fact the formation of V from III and from VI is a new type of transposition, in which III and VI lose H2O and H2S, resp., following which a group containing N migrates from a N atom to an adjacent C atom, thus: The transformation of O:C:NNH4 to O:C(NH2)2, involves only migration of a group containing N from a N atom to a C atom, without dehydration. If this were true of III, the product would be NCNH2 or HN:C:NH. Nor is the transformation of the -CONHCO- group to the -C(:NH)OCO-group, which takes place in the pyrolysis of imides, analogous to the pyrolysis of III.
Gazzetta Chimica Italiana published new progress about 7668-28-2. 7668-28-2 belongs to isothiazole, auxiliary class Sulfamide,Amine,Benzothiazole, name is 3-Aminobenzo[d]isothiazole 1,1-dioxide, and the molecular formula is C7H6N2O2S, Product Details of C7H6N2O2S.
Referemce:
https://en.wikipedia.org/wiki/Isothiazole,
Isothiazole – ScienceDirect.com