Synthesis and structural studies of a new class of heterocyclic compounds: 1,2,4-Pyridothiadiazine 1,1-dioxides, pyridyl analogues of 1,2,4-benzothiadiazine 1,1-dioxides (original) (raw)

A series of novel 1,2,4-pyridothiadiazine 1,1-dioxides (1), some of them being pyridyl analogues of the 1,2,4-benzothiadiazine 1,1-dioxide diazoxide (2), were synthesized and selected physieochemieal data (pKa, log P') were collected. By means of spectral (13C NMR, UV) and X-ray data, the most favour'able position of the C=N double bond in the thiadiazine ring was discussed. It was concluded that like 1,2,4benzothiadiazine 1,1-dioxides, 1,2,4-pyridothiadiazine l,l-dioxides free of an alkyl subsfituent in the 2-and 4positions, whatever the nitrogen atom position in the pyridine ring, show predominance of the tautomeric 4Hform.