Reaction of spiro[1,3‐benzodioxole‐benzothiazines] with hydroxylamine and active methylene compounds

Abstract

Abstract. The reactivity of the title spiranes (1) towards cleavage by different nucleophiles in ethanolic solutions has been investigated. The spiranes are cleaved by ethyl p-aminobenzoate to give 2-aryl-3-(4-methoxycarbonylphenyl)-3H-quinazoline-4-thiones (2bd) together with tetrachlorocatechol, in a manner similar to the reaction with anilines and hydrazines. However, cleavage with hydroxylamine in ethanol affords ethyl 2-(thioaroylamino)benzoates (4) in addition to the expected 2-aryl-3-hydroxy-3H-quinazoline-4-thiones (2e-f). In contrast to the situation found with amines and hydrazines, the spiranes give 4-(dicyanomethylene)-and 4-[lcyano(ethoxycarbonyl)methylene]-2-aryl-3,l-benzothiazines (5) along with the 2-(thioaroylamino)benzoates (4) when reacted with malononitrile and with ethyl cyanoacetate. In all cases, tetrachlorocatechol is produced. Reaction pathways are discussed.