(4S*)-2-Methylamino-3-nitro-4-(4-nitrophenyl)-5,6,7,8-tetrahydro-4H-chromen-5-one

The title compound, C16H15N3O6, is asymmetric with a chiral centre located in the pyran ring and crystallizes as a racemate. The six-membered carbocyclic ring adopts an envelope conformation with the central CH2 C atom as the flap. The amine N atom deviates from the mean plane of the pyran ring by 0.1365 (15) Å. The nitrophenyl ring is almost orthogonal to the pyran ring and the mean plane of the six-membered carbocyclic ring, the dihedral angle between their mean planes being 88.30 (7) and 87.61 (8)°, respectively. The molecular structure is stabilized by an intramolecular N—H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming infinite bands lying parallel to (-110) and composed of alternate R 2 2(24) and R 2 4(12) graph-set ring motifs. The crystal structure is further stabilized by C—H⋯π interactions, forming a three-dimensional structure.

The title compound, C 16 H 15 N 3 O 6 , is asymmetric with a chiral centre located in the pyran ring and crystallizes as a racemate. The six-membered carbocyclic ring adopts an envelope conformation with the central CH 2 C atom as the flap. The amine N atom deviates from the mean plane of the pyran ring by 0.1365 (15) Å . The nitrophenyl ring is almost orthogonal to the pyran ring and the mean plane of the six-membered carbocyclic ring, the dihedral angle between their mean planes being 88.30 (7) and 87.61 (8) , respectively. The molecular structure is stabilized by an intramolecular N-HÁ Á ÁO hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via C-HÁ Á ÁO hydrogen bonds, forming infinite bands lying parallel to (110) and composed of alternate R 2 2 (24) and R 2 4 (12) graph-set ring motifs. The crystal structure is further stabilized by C-HÁ Á Á interactions, forming a three-dimensional structure.
Cg1 is the centroid of the C1-C6 ring.  (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, the X-ray analysis of the title compound has been carried out to study its structural aspects.
The title compound, Fig. 1, consists of a chromene moiety attached to a nitrophenyl ring, a nitro group and a methylamine group. The molecular structure is stabilized by an intra molecular N1-H1A···O3 interaction, which generates an S(6) ring motif (Table 1 and  deviates by -0.1365 (15) Å from the mean plane of the pyran ring. The title compound exhibits structural similarities with already reported related structures (Narayanan et al., 2013a,b).
The crystal structure is further stabilized by C-H···\p interactions (Table 1) forming a three-dimensional structure.

Experimental
A solution of the requisite aldehyde (0.151 g, 1.0 mmol), cyclic 1,3-dicarbonyl compound (0.112 g, 1.0 mmol), NMSM (0.148 g, 1.0 mmol) and piperidine (0.2 equiv) in EtOH (2 ml) was stirred for 1.5 hrs. After the reaction was complete as indicated by TLC, the product was filtered and washed with EtOH (2 ml) to remove the excess base and other impurities.
Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in ethanol at room temperature.

Refinement
Positions of the hydrogen atoms were localized from difference electron density maps. The H-atoms of the amine group were refined with distance restraints of N-H = 0.90 (1) Å with U iso (H) = 1.2U eq (N U iso (H) = 1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms. The rotation angles for methyl groups were optimized by least squares.

Figure 1
The molecular structure of the title molecule, with atom labelling. The displacement ellipsoids are drawn at the 30% probability level. The intramolecular N-H···O hydrogen bond, which generates an S(6) ring motif, is shown as a dashed line (see Table 1 for details). The crystal packing of the title compound, with the C-H···O hydrogen bonds shown as dashed lines (see Table 1 for details; symmetry codes: (i) -x+1, -y+2, -z; (ii) x-1, y-1, z). 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.