1-(2,4-Dinitrophenyl)-3-phenyl-4-phenylsulfanyl-1H-pyrazole

In the title molecule, C21H14N4O4S, the pyrazole ring forms dihedral angles of 45.6 (1), 87.7 (1) and 27.4 (1)° with the phenyl, sulfur-substituted benzene and nitro-substituted benzene rings, respectively. In the crystal, molecules are connected by weak C—H⋯O and C—H⋯N hydrogen bonds into layers parallel to (010).

In the title molecule, C 21 H 14 N 4 O 4 S, the pyrazole ring forms dihedral angles of 45.6 (1), 87.7 (1) and 27.4 (1) with the phenyl, sulfur-substituted benzene and nitro-substituted benzene rings, respectively. In the crystal, molecules are connected by weak C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds into layers parallel to (010). 271 parameters H-atom parameters constrained Á max = 0.27 e Å À3 Á min = À0.14 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).  Pyrazoles are a class of aromatic ring compounds and of the heterocyclic series characterized by a 5-membered ring structure composed of three carbon atoms and two nitrogen atoms in adjacent positions and to the unsubstituted parent compound. They can have pharmacological effects on humans and are classified as alkaloids although they are rare in nature. Pyrazole and its derivatives have successfully tested for antifungal (Chen & Li, 1998), antihistaminic (Mishra et al.,1998), anti-inflammatory (Smith et al., 2001, antiarrhythmic and sedative (Bruno et al., 1990), hypoglycemic (Cottineau et al., 2002), antiviral (Baraldi et al., 1998) and pesticidal (Londershausen, 1996 activities.

Experimental
A mixture of 1-phenyl-2-(phenylsulfanyl)-1-ethanone 1-(2,4-dinitrophenyl)hydrazone (0.001 mole) dissolved in dimethylforamide (5 ml) in a 30 ml conical flask was allowed to cool in ice with stirring. To this stirred solution, phosphorus oxychloride (0.008 mole) was added dropwise and the mixture was subjected to microwave irradiation for 30 sec. The reaction was monitored by TLC and after completion of the reaction, the reaction mixture was poured onto crushed ice.
The solid was suction filtered and washed with plenty of water. The final product 1-(2,4-dinitrophenyl)-3phenyl-4-(phenylsulfanyl)-1H-pyrazole was purified by column chromatography using petroleum ether-ethyl acetate as eluent. Colourless needles were grown over a period of a week from a solution of the title compound in dichlromethane.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å and U iso (H) = 1.2 U eq (C).  The molecular structure of the title compound with 50% probability displacement ellipsoids.  Part of the crystal structure with hydrogen bonds shown as dashed lines.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.