SYNTHESIS OF 2-ACETONYL-SUBSTITUTED, 2-PHENACYL-SUBSTITUTED, AND 2-(DIOXOCYCLOALKYL)-SUBSTITUTED THIENO[2,3-D][1,3]THIAZIN-4-ONES

The reaction of ethyl 2-isothiocyanato-3-thiophenecarboxylates 1 with anions of acyclic as well as of cyclic 1,3-diketones or diethyl malona te affords diacylthioacetamide derivatives 2. Upon treatment with conc d. sulfuric acid 2a-l are transformed into novel 2-substituted thieno[ 2,3-d][1,3]thiazin-4-ones 3a-j. Ring cleavage of 3a-f with sodium alko xides gives N-(3-alkoxycarbonyl-2-thienyl)thioacetamides 4a-h.