| Abstrakt: |
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 P2[sub 1] diffractometer, MoK[sub α] radiation, graphite monochromator, θ/2θ scan mode, 2θ[sub max] = 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 P2[sub 1]/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. [ABSTRACT FROM AUTHOR] |
