Synthesis of substituted 5,6-dihydrothiopyrano [2,3-c]pyrazol-4(1H)-ones

The synthesis of substituted 5,6-dihydrothiopyranopyrazol-4(1H)-ones 3 have been developed from dihydrothiopyran-4-ones 2 and hydrazine hydrate under mild conditions in very high yields,and the products have been characterized by NMR,IR,MS and spectra elements analysis.Moreover,a mechanism for the reaction has been proposed.