Klarmann, Bodo published the artcileSaccharinimine, Synthetic Route of 7668-28-2, the publication is Chemische Berichte (1952), 162-4, database is CAplus.
Heating 10 g. o-OHCC6H4SO2Cl with 80 cc. 30% aqueous NH4OH 2 hrs. at 60° with shaking in a bomb and keeping the mixture 12 hrs. at 0° give 2.5 g. saccharinimine, m. 300°. When the reaction is carried out at 100°, 2 g. saccharin (I), m. 220°, is obtained. Warming 20 g. I with 100 cc. 30% aqueous NH4OH 7 hrs. at 60°, keeping the mixture 12 hrs., and acidifying it give unchanged I. In this reaction o-HN:CHC6H4SO2NH2 is probably formed as an intermediate in which the CH(:NH) group is then oxidized to a C(:NH)OH group, followed by cyclization by splitting off of NH3.
Chemische Berichte 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, Synthetic Route of 7668-28-2.
Referemce:
https://en.wikipedia.org/wiki/Isothiazole,
Isothiazole – ScienceDirect.com