Method of preparation of carboxamides of the oxo - 1,2 benzothiazine preferably cannot, or substantially dioxides 1,1 - - -

摘要

Disclosed herein is an improved process for the production of carboxamides of 3,4-dihydro-oxo-1,2-benzothiazine-1,1-dioxides. Said process comprises contacting either a 4-alkoxy-1,2-benzothiazine-3-carboxylic acid-1,1-dioxide or a 3-alkoxy-1,2-benzothiazine-4-carboxylic acid-1,1-dioxide with an amine followed by cleavage of the ether moiety with an appropriate reagent such as hydrogen bromide to produce a carboxanilide with previously disclosed pharmaceutical value as a non-steroidal anti inflammatory agent. The alkoxy-benzothiazine carboxylic acids are themselves novel compounds and valuable synthetic intermediates.