N′-Phenyl-N′-[3-(2,4,5-triphenyl-2,5-dihydro-1H-pyrazol-3-yl)quinoxalin-2-yl]benzohydrazide

The molecule of the title compound, C42H32N6O, is built up from one pyrazole ring linked to three phenyl rings and to an approximately planar [maximum deviation = 0.0455 (15) Å] quinoxaline system connected to a phenylbenzohydrazide group. The pyrazole ring assumes an envelope conformation, the C atom attached to the quinoxalin-3-yl ring system being the flap atom. The dihedral angle between the two phenyl rings of the phenylbenzohydrazide group is of 58.27 (9)°. The mean plane through the pyrazole ring is nearly perpendicular to the quinoxaline ring system and to the phenyl ring attached to the opposite side, forming dihedral angles of 82.58 (7) and 87.29 (9)°, respectively. An intramolecular C—H⋯O hydrogen bond is present. In the crystal, molecules are linked by pairs of N—H⋯N hydrogen bonds, forming inversion dimers, which are further connected by C—H⋯N hydrogen bonds into chains parallel to the b axis.

The molecule of the title compound, C 42 H 32 N 6 O, is built up from one pyrazole ring linked to three phenyl rings and to an approximately planar [maximum deviation = 0.0455 (15) Å ] quinoxaline system connected to a phenylbenzohydrazide group. The pyrazole ring assumes an envelope conformation, the C atom attached to the quinoxalin-3-yl ring system being the flap atom. The dihedral angle between the two phenyl rings of the phenylbenzohydrazide group is of 58.27 (9) . The mean plane through the pyrazole ring is nearly perpendicular to the quinoxaline ring system and to the phenyl ring attached to the opposite side, forming dihedral angles of 82.58 (7) and 87.29 (9) , respectively. An intramolecular C-HÁ Á ÁO hydrogen bond is present. In the crystal, molecules are linked by pairs of N-HÁ Á ÁN hydrogen bonds, forming inversion dimers, which are further connected by C-HÁ Á ÁN hydrogen bonds into chains parallel to the b axis.  Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx; Ày; Àz þ 1; (ii) x À 1 2 ; Ày þ 1 2 ; z À 1 2 .

Comment
Quinoxalinone and its derivatives are used in organic synthesis for building natural and designed synthetic compounds and have been frequently utilized as suitable skeletons for the design of biologically active compounds. For instance, they are known for their potent activity as anti-inflammatory agents (El-Sabbagh et al., 2009), inhibitors of the kinase protein (Bemis et al., 2005), anti-cancer agents (Corona et al., 2008), anti-microbial agents (Ghadage & Shirote, 2011) and are particularly effective in the treatment of diabetes and its complications (Yang et al., 2012). Our research group targeted at the development of novel quinoxalinone derivatives such as the title compound that may prove to be better agents in terms of efficacy and safety.
The molecule of the title compound displays a five membered pyrazol-5-yl ring (N1/N2/C1-C3) connected to three phenyl rings and to a quinoxalin-3-yl ring system attached to a phenylbenzohydrazide group (Fig. 1). The pyrazole ring shows an envelope conformation as indicated by the total puckering amplitude QT = 0.2552 (16) Å and spherical polar angle φ2 = 135.1 (4)°. The C3 flap atom is displaced by 0.4035 (14) Å from the mean plane through the other four atoms.
The dimers are further linked into chains parallel to the b axis by C-H···N hydrogen bonds.

Experimental
A mixture of α-chlorobenzylidene phenylhydrazine (8.1 mmol) and triethylamine (8.1 mmol) in THF (40 mL) was added at room temperature to a solution of 3-styryl-quinoxalin-2-one (6.5 mmol) in THF (20 mL). The reaction mixture was heated under reflux for 48 h. The inorganic salts formed were filtered off. The filtrate was evaporated under reduced pressure and the crude product obtained was recrystallized from ethanol to afford crystals of the title compound.

Refinement
All H atoms could be located in a difference Fourier map and were treated as riding with C-H = 0.93 Å, N-H = 0.89 Å and with U iso (H) = 1.2 U eq (C, N). Six reflections affected by the beam stop were omitted because the difference between their calculated and observed intensities was very large.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are represented as small circles of arbitrary radii.

N′-Phenyl-N′-[3-(2,4,5-triphenyl-2,5-dihydro-1H-pyrazol-3-yl)quinoxalin-2-yl]benzohydrazide
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.20 e Å −3 Δρ min = −0.19 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0019 (4) Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.