7,7-Dimethyl-2-methylamino-4-(4-methylphenyl)-3-nitro-7,8-dihydro-4H-chromen-5(6H)-one

In the title compound, C19H22N2O4, the six-membered cyclohexenone ring of the chromene unit adopts an envelope conformation, with the dimethyl-substituted C atom as the flap, while the pyran ring has a boat conformation. These two mean planes are inclined to one another by 6.65 (13)°·The benzene ring is normal to the 4H-chromene moiety mean plane, making a dihedral angle of 89.18 (5)°. The methylamine and nitro groups are slightly twisted from the chromene moiety mean plane, with torsion angles C—N—C—O = 1.70 (18) and O—N—C—C = 0.15 (18)°. The molecular structure is characterized by an intramolecular N—H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via pairs of weak C—H⋯O hydrogen bonds, forming inversion dimers. These dimers are connected by further C—H⋯O hydrogen bonds, forming sheets lying parallel to (10-1).

In the title compound, C 19 H 22 N 2 O 4 , the six-membered cyclohexenone ring of the chromene unit adopts an envelope conformation, with the dimethyl-substituted C atom as the flap, while the pyran ring has a boat conformation. These two mean planes are inclined to one another by 6.65 (13) ÁThe benzene ring is normal to the 4H-chromene moiety mean plane, making a dihedral angle of 89.18 (5) . The methylamine and nitro groups are slightly twisted from the chromene moiety mean plane, with torsion angles C-N-C-O = 1.70 (18) and O-N-C-C = 0.15 (18) . The molecular structure is characterized by an intramolecular N-HÁ Á ÁO hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via pairs of weak C-HÁ Á ÁO hydrogen bonds, forming inversion dimers. These dimers are connected by further C-HÁ Á ÁO hydrogen bonds, forming sheets lying parallel to (101).
The title compound, Fig. 1, consists of a chromene unit connected to a toluene ring at C11, a nitro group at C12, a methyl amine group at C13, dimethyl group at C16 and an oxygen atom at C18. The benzene ring (C1-C6) is normal to the mean plane of chromene unit (O1/C11-C19) with a dihedral angle of 89.18 (5)°. The nitro and methylamine groups are inclined to the mean plane of chromene unit by 6.51 (8) and 5.42 (6)°, respectively.
In the crystal, molecules are linked via pairs of C-H···O hydrogen bonds forming inversion dimers ( Fig. 2 and Table   1). These dimers are connected by further C-H···O hydrogen bonds forming sheets lying parallel to (10-1) [ Table 1 and Fig. 2]. The nitro atom O3 is involved in both intra-and inter-molecular hydrogen bonding, having a bifurcated character.

Experimental
A solution of 4-methylbenzaldehyde (1.0 mmol), 5,5-dimethylcyclohexane-1,3-dione (1.0 mmol), NMSM (1.0 mmol), and piperidine (0.2 equiv) in ethanol (2 ml) was stirred for 3.5 h. After the reaction was complete, as indicated by TLC, the product was filtered and washed with 2 ml of ethanol, to remove the excess base and other impurities. Finally, the product was recrystallized from ethanol yielding colourless block-like crystals.

Refinement
H atoms were placed in idealized positions and allowed to ride on the parent atoms: N-H = 0.86 Å, and C-H = 0.93, 0.96 and 0.97 Å for aromatic, methyl and methylene H atoms, respectively, with U iso (H)= 1.5 U eq (C-methyl) and = 1.2U eq (C,N) for other H atoms.  A view of the molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level. The intramolecular hydrogen bond is shown as a dashed line (see Table 1 for details).  The crystal packing of the title compound viewed along the c axis. Hydrogen bonds are shown as dashed lines (see Table   1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity). 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.  (7) 0.0044 (7) 0.0147 (6) −0.0007 (6)  C3 0.0481 (7) 0.0391 (7) 0.0363 (6)