Schapira, Celia B. published the artcile3-Oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide derivatives. I. Reaction of esters with alkoxides, Application In Synthesis of 7668-28-2, the publication is Journal of Heterocyclic Chemistry (1980), 17(6), 1281-8, database is CAplus.
Reaction of the benzisothiazolineacetic acids I (R = Me, Et, Me2CH, Me2CHCH2CH2, Ph) with alk. alkoxides was carried out under various conditions. Under mild conditions, o-(RO2C)C6H4SO2NHCH2COR (II) were obtained with good yields. Reaction of I or II with Na alkoxides under drastic conditions gave the esters III. Transesterification was observed when esters I were treated with NaOMe. Esters III were hydrolyzed in concentrated aqueous NaOH giving the acid III (R = H). Attempts to recrystallize III (R = H) from water resulted in its decarboxylation to give 2H-1,2-benzothiazin-4(3H)one 1,1-dioxide. III(R = H) could not be obtained by acid hydrolysis of esters III or by rearrangement of 3-oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide. The rearrangement apparently took place by ethanolysis of the carboxamide linkage to the open sulfonamides (fast step) followed by a Dieckmann cyclization (slow step). Transesterification took place in the open sulfonamides.
Journal of Heterocyclic Chemistry 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, Application In Synthesis of 7668-28-2.
Referemce:
https://en.wikipedia.org/wiki/Isothiazole,
Isothiazole – ScienceDirect.com