A monoclinic modification of (4Z)-1-benzyl-4-(2-oxopropylidene)-2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-2-one

Laboratoire de Chimie Organique Hétérocyclique, Centre de Recherche des Sciences des médicaments, URAC 21, Pôle de Compétence Pharmacochimie, Av Ibn Battouta, BP 1014, Faculté des Sciences, Université Mohammed V, Rabat, Morocco, Unité de Chimie Moleculaire et Environnement, Faculté des Sciences et, Techniques, Université de Sciences, de Technologie et de Médecine, Nouakchott, Mauritania, and Department of Chemistry, Tulane University, New Orleans, LA 70118, USA. *Correspondence e-mail: sam.mmohamed18@gmail.com

In the title molecule, C 19 H 18 N 2 O 2 , the orientation of the oxopropylidene substituent is largely determined by an intramolecular N-HÁ Á ÁO hydrogen bond. In the crystal, C-HÁ Á ÁO hydrogen bonds form zigzag chains, which are elaborated into sheets lying parallel to (101) by complementary C-HÁ Á Á interactions. Comparisons to the structure of the triclinic modification are made.

Structure description
Benzodiazepine derivatives are widely used as anticonvulsants, antidepressives, sedatives and analgesics (Schultz et al., 1982;Olkkola et al., 2008). In addition, they are used as medicinal agents in the treatment of central nervous system (CNS) disturbances (Stefancich et al., 1992). They also exhibit antitumor and antineoplastic activities (Werner et al., 1990). As part of our ongoing studies in this area (Sebhaoui et al., 2016(Sebhaoui et al., , 2017 we now describe the synthesis and crystal structure of a monoclinic modification of the title compound to complement the known triclinic polymorph (Samba et al., 2016).

Figure 3
Packing viewed along the a-axis direction with intermolecular interactions depicted as in Fig. 2.

Figure 1
The title molecule with the labelling scheme and 50% probability ellipsoids. The intramolecular N-HÁ Á ÁO hydrogen bond is shown as a dashed line. Table 1 Hydrogen-bond geometry (Å , ).

Synthesis and crystallization
(4Z)-4-(2-Oxopropylidene)-1,5-benzodiazepin-2-one (0.01 mol) and potassium carbonate K 2 CO 3 (0.02 mol) were dissolved in DMF, then benzylbromide (0.02 mol) and tetrabutylammonium bromide as a phase-transfer catalyst (0.001 mol) were added. The reaction mixture was stirred at room temperature for 48 h. The residue obtained, after evaporation of solvent, was chromatographed on a silica gel column using a hexane/ethyl acetate 9:1 mixture as eluent. The solid obtained was crystallized from dichloromethane solution to afford as colourless blocks. The triclinic modification was crystallized from ethanol solution (Samba et al., 2016).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

data-1
IUCrData ( Special details Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 15 sec/frame. 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. Independent refinement of the hydrogens attached to C19 led to an unsatisfacory geometry so they were placed in calculated positions and included as riding contributions. Independent refinement of the H atoms attached to C19 led to an unsatisfacory geometry so they were placed in calculated positions and included as riding contributions.