Crystal structure of (4Z)-4-[(dimethylamino)methylidene]-3,5-dioxo-2-phenylpyrazolidine-1-carbaldehyde

In the title compound, C13H13N3O3, the pyrazolidine ring adopts a shallow envelope conformation, with the carbonyl C atom closest to the benzene ring as the flap [deviation of 0.126 (1) Å from the plane through the remaining atoms (r.m.s. deviation = 0.011 Å)]. The dihedral angle between the pyrazolidine ring (all atoms) and the benzene ring is 51.09 (4)°. An extremely short (2.08 Å) intramolecular C—H⋯O contact is seen. In the crystal, molecules are linked by C—H⋯O bonds, generating [010] chains. Extremely weak C—H⋯π interactions are also observed.

Tulane Crystallography Laboratory are gratefully acknowledged.
Supporting information for this paper is available from the IUCr electronic archives (Reference: HB7425). Azole compounds are extensively studied and widely used as anti-microbial agents (Patel et al., 2012;Vijesh et al., 2011). Recently, urea derivatives of pyrazole have been reported as potent inhibitors of p38 kinase (Jin et al., 2011).
Many of other pyrazole scaffold compounds are reported to have broad spectra of biological activities, such as antifungal (Zhang et al., 2010), anti-viral (El-Sabbagh et al., 2009, anti-inflammatory (Dekhane et al., 2011), anti-tumor, anti-HCV (Rostom et al., 2003), herbicidal (Zhou et al., 2010) and insecticidal activities (Finkelstein & Strock, 1997). In view of such findings and as a continuation of our study on the synthesis of potential bio-active heterocyclic molecules, we report here the synthesis and crystal structure of the title compound.
In the title compound, the pyrazolidine ring is slightly twisted with an r.m.s. deviation from the mean plane of the 5 atoms forming the ring of 0.036 Å. The dihedral angle between this plane and that of the phenyl ring is 51.09 (4)° ( Fig.   1).

S2. Experimental
To phosphorous oxychloride (0.1 mol, 10 ml), in a conical flask with a magnetic stirrer, dry dimethylformamide (35 ml) was added drop-wise with stirring at 303-308 K for 30 min. Then a solution of 1-phenylpyrazolidine-3,5-dione (0.05 mol, 8.8 g) in dimethylformamide (15 ml), was added drop-wise with continuous stirring while ensuring that the temperature did not exceed 318 K. The reaction mixture was stirred overnight and poured onto crushed ice. The solid product was collected by filtration and recrystallized from ethanol to give colourless crystals in 75% yield (m. p. 453-455 K). The title molecule with 50% probability ellipsoids.

Figure 2
Packing viewed down the b axis. C-H···π interactions are shown by dotted lines.

Special details
Experimental. Analysis of 3764 reflections having I/σ(I) > 12 and chosen from the full data set with CELL_NOW (Sheldrick, 2008) showed the crystal to belong to the monoclinic system and to be twinned by a 180° rotation about the c* axis. The raw data were processed using the multi-component version of SAINT under control of the two-component orientation file generated by CELL_NOW. 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 Rfactors based on ALL data will be even larger. H-atoms were placed in calculated positions (C-H = 0.95 -0.98 Å) and included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached carbon atoms. The model was refined as a 2-component twin.