Crystal structure of 2-amino-4-(4-methoxyphenyl)-4H-benzo[g]chromene-3-carbonitrile

In the title compound, C21H16N2O2, the naphthalene fragment is twisted slightly, as indicated by the dihedral angle of 3.2 (2)° between the two six-membered rings. The pendant 4-methoxyphenyl ring makes a dihedral angle of 86.08 (6)° with the central six-membered ring of the 4H-benzo[g]chromene ring system. In the crystal, molecules are linked by pairs of N—H⋯N hydrogen bonds, forming inversion dimers which are linked into chains propagating in the b-axis direction by N—H⋯O hydrogen bonds.

In continuation of our interest in the chemical and pharmacological properties of 4H-chromene and fused 4H-chromene derivatives, we herein report on the synthesis and crystal structure of the title compound.
In the crystal, pairwise N2-H2A···N1 i hydrogen bonds form inversion dimers which are linked into chains running along the b axis direction ( Fig. 2 and Table 1). The overall packing of these units in the crystal is illustrated in Fig. 3.

S2. Synthesis and crystallization
To a solution of 4-methoxybenzylidene-malononitrile (1 mmol, 180 mg) in 10 ml of ethanol was added 4-1-naphthol (1 mmol, 144 mg) in the presence of few catalytic drops of piperedine and the temperature was adjusted at 353 K for 1 h. A solid product was obtained on cooling, collected by filtration and recrystallized from ethanol to afford colorless plate-like crystals suitable for X-ray diffraction analysis.

S3. Refinement
The NH 2 H-atoms were located in a difference Fourier map and freely refined. The C-bound H atoms were placed in calculated positions (C-H = 0.95 − 1.00 Å) and included as riding contributions with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound with the labeling scheme and 50% probability displacement ellipsoids.

Figure 2
View along the c axis of one hydrogen-bonded layer. The N-H···N and N-H···O hydrogen bonds (see Table 1) are shown as blue and purple dotted lines, respectively.

Figure 3
Crystal packing viewed along the c axis, with the N-H···N and N-H···O hydrogen bonds (see Table 1) shown as blue and purple dotted lines, respectively.