Ft. Coppo et Mm. Fawzi, SYNTHESIS OF PYRAZOLO[3,4-C][1,2]THIAZIN-4(3H)-ONE 2,2-DIOXIDES, NEW HETEROCYCLES, Journal of heterocyclic chemistry, 34(6), 1997, pp. 1693-1697
The reaction of substituted ethyl 5-aminopyrazole-4-carboxylates with
two equivalents of methanesulfonyl chloride gave the substituted ethyl
is(methylsufonyl)amino]-1H-pyrazole-4-carboxylates II. Removal of one
of the methanesulfonyl groups, followed by alkylation of the ethyl [(
methylsulfonyl)amino]-1H-pyrazole-4-carboxylates III with methyl iodid
e produced the substituted ethyl l(methylsulfonyl)amino]-1H-pyrazole-4
-carboxylates IV. Treatment of IV with sodium hydride gave the 7-subst
ituted ydro-1-methylpyrazolo[3,4-c][1,2]thiazin-4(3H)-one 2,2-dioxides
V.