4-(1-METHYL-2-SULFAMOYLVINYL)PYRAZOLES BY RING TRANSFORMATION OF 1,1-DIOXO-2H-1,2-THIAZINE-4-CARBALDEHYDE WITH HYDRAZINES

As masked 1,3-dicarbonyl compounds, 1,1-dioxo-2H-1,2-thiazine-4-carbal dehydes (2a-e, 7) undergo ring transformations with nucleophilic hydra zines to produce 4-[1-methyl-2-(arylsulfamoyl)vinyl]pyrazoles (9a-i). For 9h, an X-ray structural analysis is reported. With less nucleophil ic semicarbazide and p-nitrophenylhydrazine the hydrazones (11a,b) wer e isolated. The carbaldehydes 2a-e, 7 and 8a,b were synthesized by for mylation of the 1,1-dioxo-2H-1,2-thiazines 1a-e, 5 and 6a,b with dichl oromethyl methyl ether/TiCl4. In the case of 1a-e mixtures of 4- and 6 -carbaldehydes (2a-e/3a-e) were obtained, which, however, could be use d for the synthesis of pyrazoles.