Crystal structure of 4-(6-bromo-4-oxo-4H-chromen-3-yl)-2-methylamino-3-nitropyrano[3,2-c]chromen-5(4H)-one chloroform monosolvate

In the title compound, C22H13BrN2O7·CHCl3, the pyran ring adopts a shallow sofa conformation with the C atom bearing the bromochromene system as the flap [deviation = 0.291 (3) Å]. The dihedral angle between the pyran fused-ring system (all atoms; r.m.s. deviation = 0.032 Å) and the bromochromene ring system (r.m.s. deviation = 0.027 Å) is 87.56 (9)°. An intramolecular N—H⋯O hydrogen bond closes an S(6) ring. The Cl atoms of the solvent molecule are disordered over two sets of sites in a 0.515 (6):0.485 (6) ratio. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(12) loops. The packing also features C—H⋯O and very weak π–π [centroid–centroid separation = 3.960 (2) Å] interactions, which link the dimers into a three-dimensional network.


S1. Comment
Chromene derivatives are heterocyclic compounds that have a variety of industrial, biological and chemical synthesis 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, etc. (Khan et al., 2010;Raj et al., 2010). Against this background an X-ray diffraction study of the title compound and its structural aspects are presented herein.
Upon completion of the reaction, the mixture was filtered, and washed with ethanol to obtained desired white product in 93% yield. Colourless blocks of the title compound were recrystallised from chloroform solution.

S3. Refinement
N and C-bound H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for all other H atoms.

Figure 1
The molecular structure of the title molecule, with displacement ellipsoids drawn at 30% probability level. The intramolecular hydrogen bond, which generates an S(6) ring motif, is shown as a dashed line.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (