Crystal structure of 2-methylamino-4-(6-methyl-4-oxo-4H-chromen-3-yl)-3-nitropyrano[3,2-c]chromen-5(4H)-one with an unknown solvate

In the title compound, C23H16N2O7, the mean planes of the two chromene units (r.m.s. deviations = 0.031 and 0.064 Å) are almost normal to one another with a dihedral angle of 85.59 (6)°. The central six-membered pyran ring has a distorted envelope conformation, with the methine C atom at the flap. There is an intramolecular N—H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(12) ring motif. The dimers are linked by pairs of C—H⋯O hydrogen bonds, enclosing R 2 2(6) ring motifs, forming zigzag chains along [001]. The chains are linked by a second pair of C—H⋯O hydrogen bonds, forming slabs parallel to (110). Within the slabs there are C—H⋯π interactions present. A region of disordered electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9–18] following unsuccessful attempts to model it as plausible solvent molecule(s). The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).


S1. Comment
Chromene derivatives are important heterocyclic compounds that have a variety of industrial, biological and chemical synthetic applications (Geen et al., 1996;Ercole et al., 2009). They exhibit a number of pharmacological activities such as anti -HIV, anti-inflammatory, anti-bacterial, anti-allergic, anti-cancer (Khan et al., 2010;Raj et al., 2010). Against this background, we synthesized the title compound and report herein on its crystal structure.
In the crystal, molecules are linked by pairs of N-H···O hydrogen bonds forming inversion dimers with an R 2 2 (12) ring motif. The dimers are linked by pairs of C-H···O hydrogen bonds, enclosing R 2 2 (6) ring motifs, forming zigzag chains along [001]. The chains are linked by a second pair of C-H···O hydrogen bonds forming slabs parallel to (110). Within the slabs there are C-H···π interactions present. Details of the hydrogen bonding and other interactions are given in Table 1 and Fig. 2.

S2. Synthesis and crystallization
The title compound was prepared by a three component coupling reaction in the presence of indium(III) chloride as a Lewis acid catalyst. The combination of ethanol and InCl 3 gave an excellent result with a short reaction time. To a solution of 4-hydroxycoumarin (0.81 g, 5 mmol), 6-methyl-4-oxo-4H-chromene-3-carbaldehyde (0.97 g, 5 mmol) and NMSM (0.74 g, 5 mmol) in EtOH at room temperature was added indium(III) chloride (0.2 eq). Upon completion of the reaction (monitored by TLC) after 2 h, the mixture was filtered, and washed with ethanol to obtained the desired product (yield = 93%).

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH H atom was located in a difference Fourier map and freely refined. The C-bound H atoms were positioned geometrically and allowed to ride on supporting information sup-2 . E71, o645-o646 their parent atoms: C-H = 0.93-0.98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms. A region of disordered electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71,[9][10][11][12][13][14][15][16][17][18] following unsuccessful attempts to model it as plausible solvent molecules. The given chemical formula and other crystal data do not take into account the unknown solvent molecules.

Figure 1
The molecular structure of the title compound, with the atom labelling. The displacement ellipsoids are drawn at 30% probability level.  The crystal packing of the title compound, viewed along the a axis. The hydrogen bonds are shown as dashed lines (see Table 1 for details).  (2) 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.