3-Methyl-5-oxo-4-(2-phenylhydrazinylidene)-4,5-dihydro-1H-pyrazole-1-carbothioamide

In the title compound, C11H11N5OS, the pyrazole ring is approximately planar, with a maximum deviation of 0.010 (2) Å. The dihedral angles between the benzene ring and the pyrazole and carbothioamide groups are 5.42 (9) and 10.61 (18)°, respectively. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are connected by intermolecular N—H⋯O and C—H⋯S hydrogen bonds, forming R 2 2(12) ring motifs. In addition, there is a π–π stacking interaction [centroid–centroid distance = 3.5188 (11) Å] between the pyrazole and benzene rings. These interactions link the molecules into infinite chains along [001].

In the title compound, C 11 H 11 N 5 OS, the pyrazole ring is approximately planar, with a maximum deviation of 0.010 (2) Å . The dihedral angles between the benzene ring and the pyrazole and carbothioamide groups are 5.42 (9) and 10.61 (18) , respectively. An intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring motif. In the crystal, molecules are connected by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁS hydrogen bonds, forming R 2 2 (12) ring motifs. In addition, there is astacking interaction [centroidcentroid distance = 3.5188 (11) Å ] between the pyrazole and benzene rings. These interactions link the molecules into infinite chains along [001].

Comment
Pyrazole derivatives are in general well-known nitrogen-containing heterocyclic compounds and various procedures have been developed for their synthesis (Rai & Kalluraya, 2006). The chemistry of pyrazole derivatives has been the subject of much interest due to their importance for various applications and their widespread potential and proven biological and pharmacological activities (Rai et al., 2008). Steroids containing a pyrazole moiety are of interest as psychopharmacological agents. Some alkyl-and aryl-substituted pyrazoles have a sharply pronounced sedative action on the central nervous system. Furthermore, certain alkyl pyrazoles show significant bacteriostatic, bacteriocidal, fungicidal, analgesic and anti-pyretic activities (Sridhar & Perumal, 2003). Fig.1 shows the molecular structure of (I). The pyrazole (C7-C9/N3/N4) ring is approximately planar with a maximum deviation of 0.010 (2) Å for atom C8. The dihedral angle between benzene and pyrazole rings is 5.42 (9)°. The carbothioamide group (S1/C11/N5) is twisted at a dihedral angle 10.61 (18)° from the pyrazole ring. The bond lengths (Allen et al., 1987) in (I) show normal values. An intramolecular N1-H1B···O1 hydrogen bond (Table 1) generates an S(6) ring motif (Bernstein et al., 1995).

Experimental
To a solution of ethyl-3-oxo-2-(2-phenylhydrazinylidene) butanoate (0.01mol) dissolved in glacial acetic acid (20ml), a solution of thiosemicarbazide (0.02mol) in glacial acetic acid (25ml) was added and the mixture was refluxed for 4 h. It is cooled and allowed to stand overnight. The solid product that separated out was filtered and dried. It was then recrystallized from ethanol. Crystals suitable for X-ray analysis were obtained from 1:2 mixtures of DMF and ethanol by slow evaporation.

Refinement
All the H atoms were placed in calculated positions with N-H = 0.86Å, C-H = 0.93Å, and for C-H 3 = 0.96Å. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.