Ring transformation of 6-acyl-1,1-dioxo-1,2-thiazines with nitrogen nucleophiles to substituted pyridinium-3-sulfonamidates

6-Acyl(benzoyl)-1,1-dioxo-1,2-thiazines 2 were synthesized by Friedel-Craft s acylation of the 3,5-dimethyl-1,l-dioxo-l,2-thiazines 1 and 3 using carbo xylic anhydrides. The ketones 2 and 4 were transformed to substituted pyrid inium-3-sulfonamidates 5-7 and 9 with nitrogen nucleophiles like alkylamine s and hydrazine. A pyrido-pyridazinum-sulfonamidate 8 was formed from 2e wi th hydrazinium hydroxide. The 6-benzoyl-1,1-dioxo-1,2-thiazine 29 does not show the described ring transformation. The results demonstrate scope and l imitations of the ring transformation reaction of 1,1-dioxo-1,2-thiazine-6- carbonyl compounds.