Synthesis of pyrazolo[3,4-c][1,2]thiazin-4(3H)-one 2,2-dioxides,new heterocycles

The reaction of substituted ethyl 5-aminopyrazole-4-carboxylates with two equivalents of methanesul-fonyl chloride gave the substituted ethyl 5-bis(methylsufonyl)amino]-1H.-pyrazole-4-carboxylates II . Removal of one of the methanesulfonyl groups, followed by alkylation of the ethyl 5-(methylsulfonyl)amino]-1H-pyrazole-4-carboxylates III with methyl iodide produced the substituted ethyl 5-methyl(methylsulfonyl)amino]-1H-pyrazole-4-carboxylates IV . Treatment of IV with sodium hydride gave the 7-substituted 1,7-dihydro-1-methylpyrazolo3,4-c]1,2]thiazin-4(3H)-one 2,2-dioxides V .