76508-37-7Relevant articles and documents
3-Oxo-1,2-benzoisothiazoline-2-acetic Acid 1,1-Dioxide Derivatives. I. Reaction of Esters with Alkoxides
Schapira, Celia B.,Perillo, Isabel A.,Lamdan, Samuel
, p. 1281 - 1288 (2007/10/02)
Reaction of 3-oxo-1,2-benzoisothiazoline-2-acetic acid alkyl esters 1,1-dioxide (1a-d) with alkaline alkoxides was carried out under various conditions.Under mild conditions, o-(N-carboxymethylsulfamyl)benzoic acids dialkyl esters (2a-d) were obtained with good yields.Reaction of 1a-d or 2a-d with sodium alkoxide under drastic conditions afforded 4-hydroxy-2H-1,2-benzothiazine-3-carboxylic acid alkyl esters 1,1-dioxide (3a-d).Transesterification was observed when esters 1b-d were treated with sodium methoxide in methanol.Esters 3a-d were hydrolyzed in concentrated aqueous sodium hydroxide affording the acid 6.Attempts to recrystallize 6 from water resulted in its decarboxylation to give 2H-1,2-benzothiazine-4-(3H)one 1,1-dioxide (7).Compound 6 could not be obtained by acid hydrolysis of esters 3a-d or by rearrangement of 3-oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide (8).Different experimental evidence supports the suggestion that rearrangement took place by ethanolysis of the carboxamide linkage affording the open sulfonamides (fast step) followed by a Dieckmann cyclization (slow step).It was demonstrated that transesterification took place in the open sulfonamides 2.
