Crystal structure of 4-(4-methoxyphenyl)-7,7-dimethyl-2-methylamino-3-nitro-7,8-dihydro-4H-chromen-5(6H)-one

In the title compound, C19H22N2O5, the six-membered carbocyclic ring of the chromene moiety adopts an envelope conformation with the dimethyl-substituted C atom as the flap. The pyran ring has a flat-boat conformation. The methoxyphenyl ring is orthogonal to the mean plane of the chromene moiety, with a dihedral angle of 89.97 (8)°. The amine N atom deviates from the chromene mean plane by 0.1897 (16) Å. The methylamine and the nitro group are involved in an intramolecular N—H⋯O hydrogen bond which generates an S(6) ring motif. They are slightly twisted out of the plane of the chromene moiety with torsion angles of C—N—C—O(pyran) = 2.2 (3)° and O(nitro)—N—C—C = −5.6 (2)°. In the crystal, there are only C—H⋯π interactions present, forming inversion-related dimers.


S1. Comment
Amino chromenes and their derivatives are an important class of heterocyclic compounds having significant biological activities. During the last decade, such compounds have shown interesting pharmacological properties including antimicrobial, mutagenicity, sex hormone, cancer therapy, and central nervous system activities (Shah et al., 2013).
The title compound, Fig. 1, consists of a chromene unit attached to a methoxyphenyl ring, a nitro group, a dimethyl, a methyl-amine group and an oxygen atom. The mean plane of the chromene unit (O1/C7-C15) makes a dihedral angle of 89.87 (8)° with the phenyl ring (C1-C6), which shows that they are perpendicular to each other. The mean plane of the chromene unit makes dihedral angles of 5.56 (11) and 5.46 (9)° with the nitro and methylamine groups, respectively.
The molecular structure is characterized by an intramolecular N-H···O hydrogen bond, generates an S(6) ring motif (Table 1).
In the crystal, there are only C-H···π interactions present (Table 1).

S2. Experimental
A solution of 4-methoxylbenzaldehyde (1.0 mmol), 5,5-dimethylcyclohexane-1,3-dione (1.0 mmol), NMSM (1.0 mmol), and piperidine (0.2 eq) in the presence of ethanol (2 ml) was stirred for 5 h. After the reaction was complete, as indicated by TLC, the product was filtered out and washed with 2 ml of ethanol to remove the excess base and other impurities.
The resulting products were recrystallized from ethanol yielding crystal of the title compound.

S3. Refinement
H atoms were placed in idealized positions and allowed to ride on the parent atoms: N-H = 0.86 Å, C-H = 0.93 -0.97 Å with U iso (H)= 1.5U eq (C-methyl) and = 1.2U eq (N,C) for other H atoms.
supporting information

Figure 1
A view of the molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

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.