N,N-Dialkyl-N'-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part X.* The First Pyrazolo[1,5-b][1,2,4,6]thiatriazine Derivatives and their Unusual Reactions with Acylating Agents

N,N-dialkyl-N′-chlorosulfonyl chloroformamidines 1 underwent a regioselective reaction with 3-aminopyrazoles 2 to produce pyrazolo[1,5-b][1,2, 4,6]thiatriazines 3, representatives of a new ring system. Attempted N-acylation of compounds 3 with acetic anhydride (or chloride) and benzoyl chloride in pyridine, only afforded 5-(pyridin-4-yl)-pyrazolo[1,5-b][1,2,4,6]thiatriazine derivatives 11. The analogous reaction with pyridazine led to the corresponding pyridazin-4-yl derivative.