Synthesis and IR and NMR spectroscopic studies of amino derivatives of oxo-, thio-, and selenopyrazole. Crystal and molecular structure of 1-phenyl-3-methyl-4-methylene-(N-8-aminoquinoline)-5-oxopyrazole

Three compounds of the pyrazole series—o-oxo, thio, and seleno derivatives—have been synthesized and characterized by IR and NMR spectroscopy. The crystal structure of the oxo derivative is determined (Syntex P21 diffractometer, MoKα radiation, graphite monochromator, θ/2θ scan mode, 2θmax = 57°, direct method, anisotropic—isotropic (H) least-squares refinement for 2015 reflections, R = 0.043, wR2 = 0.1084). The crystals are monoclinic, a = 7.543(1) Å, b = 7.850(2) Å, c = 27.909(6) Å, β = 93.79(3)°, Z = 2, and space group P21/c. It is found that the o-hydroxyazomethine derivatives of the pyrazolone series exist in the crystal as 4-aminomethylene-5-oxo tautomers. The proton is localized at the exocyclic N atom. It lies in the plane of the main molecular fragment and participates in the intramolecular bifurcate N—H⋯O(N) hydrogen bond, which closes the six-membered and five-membered H-rings, respectively.