Crystal structure of 13-phenyl-2,3,4,13-tetrahydro-1H-indazolo[1,2-b]phthalazine-1,6,11-trione

The title compound, C21H16N2O3, consists of an indazolone moiety, bearing a phenyl group, fused to a phthalazine ring system (r.m.s. deviation = 0.018 Å). The phenyl ring is almost normal to the mean plane of the five-membered ring of the indazolone moiety, making a dihedral angle of 89.64 (7)°. The six-membered ring of the indazolone moiety has an envelope conformation, with the central methylene C atom as the flap. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming slabs parallel to the bc plane. The slabs are linked via C—H⋯π and π–π interactions [the shortest inter-centroid distance involving rings of pyrazolophthalazine moieties is 3.6430 (8) Å], forming a three-dimensional structure.


S1. Comments
Phthalazine derivatives have been reported to act as anticonvulsants (Carling et al. 2004), potential inhibitors of serotonin reuptake (Cashman & Ghirmai, 2009), anti-proliferative agents against different human and murine tumor cells (Hall et al., 1992(Hall et al., , 2001) and vasorelaxant agents (Nomoto et al. 1990). Therefore, a number of synthetic methods have been developed in recent years to uncover a variety of new reagents for the synthesis of phthalazine derivatives (Mosaddegh & Hassankhani, 2011;Hasaninejed et al., 2012;Keshipour et al., 2012). In previous work, we have reported the synthesis and structure heterocyclic compounds bearing a phthalazine unit (Bouraiou et al., 2015). Herein, we describe the synthesis and crystal structure of the title indazolo phthalazine-trione derivative, resulting from the reaction of phthalhydrazide, cyclohexa-1,3-dione and benzaldehyde in the presence of catalytic amounts of sulfuric acid.

S2. Synthesis and crystallization
The title compound was synthesized in accordance with established methods (Khurana & Magoo, 2009;Bouraiou et al., 2015). Spectroscopic results and physical properties are in agreement with literature reports (Nagarapu et al., 2009

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The H atoms were located in difference Fourier maps but introduced in calculated positions and refined as riding atoms: C-H = 0.93-0.98 Å with supporting information

Figure 1
The molecule structure of the title compound, with atom labelling. Displacement are drawn at the 50% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound, showing the C-H···O hydrogen bonds as dashed lines (see Table 1). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.6 e Å −3 Δρ min = −0.28 e Å −3 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.