Various [5,6]pyrano[2,3-c]pyrazol-4(1H)-thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3-c]pyrazol-4(1H)-ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts ((1)H, (13)C, (15)N) and coupling constants ((1)H,(1)H; (13)C,(1)H) was achieved by the combined application of various one- and two-dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most (13)C,(1)H spin coupling constants is accomplished by 2D (delta, J) long-range INEPT spectra with selective excitation.

The title compound is prepared by treatment of 1-phenylpyrazolo[4',3':5,6]pyrano[3,2-c]pyridin-4(1H)-one with Lawesson’s reagent in refluxing toluene. Detailed spectroscopic data (1H NMR, 13C NMR, 15N NMR, MS) are presented