3‐Oxo‐1,2‐benzoisothiazoline‐2‐acetic acid 1,1‐dioxide derivatives. II. Reaction of amides with alkoxides

Reaction of some 3‐oxo‐1,2‐benzoisothiazoline‐2‐acetamide 1,1‐dioxides ( 1a‐f ) with alkaline alkoxides was carried out under various conditions. Under mild conditions, 1a‐f with sodium methoxide gave o‐( N ‐carbox‐amidomethylsulfamyl)benzoic acid methyl esters ( 2a‐f, R = CH3 ). Compounds 1a or 2a reacted with sodium alkoxides under drastic conditions affording only ester 5 . Under the same conditions, 1b‐d or 2b‐d gave 4‐hydroxy‐2 H ‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxides ( 3b‐d ), while 1e‐f or 2e‐f afforded the acid 6 in variable amounts, together with the expected benzothiazines 3e‐f . Isolation of ethyl ether as another product in the reaction of 1e‐f with sodium ethoxide supports the suggestion that the formation of 6 involves the O‐alkyl fission on the alkyl carbon of the esters 2e‐f . An explanation of these results may be related to the acidic character of the amide hydrogen in compounds 2e‐f .