Crystal structure of 2-amino-4-phenyl-4H-benzo[h]chromene-3-carbonitrile

In the title compound, C20H14N2O, the plane of the phenyl ring is almost normal to that of the naphthalene ring system, forming a dihedral angle of 83.15 (8)°. The 4H-pyran ring fused with the naphthalene ring system has a flattened boat conformation. In the crystal, molecules are linked by pairs of N—H⋯N hydrogen bonds, forming inversion dimers with an R 2 2(12) ring motif. The dimers are connected by C—H⋯π interactions, forming supramolecular chains along [010].

Cg1 is the centroid of the C15-C20 phenyl ring.

S1. Comment
Among synthetic heterocyclic compounds, aminochromenes represent an important class of organic compounds being the main components of many naturally occurring products (Elagamey et al., 1988;El-Maghraby, 2014). They are used for the chemical synthesis of cosmetics, pigments (Ellis, 1977), and potentially biodegradable agrochemicals (Hafez, et al., 1987). Fused chromene systems have displayed a broad spectrum of biological activities such as mutagenicity (Hiramoto, et al., 1997), sex pheromonal (Bianchi & Tava, 1987), central nervous system (CNS) activities (Eiden & Denk, 1991) and inhibitors for influenza virus sialidases Taylor et al., 1998). In this context and following our strategy for the synthesis of bio-active molecules, we herein report the synthesis and crystal structure of the title compound.

S2. Experimental
To a solution of 1-naphthol (144 mg; 1 mmol) in 10 ml absolute ethanol, an equimolar amount of benzylidene-malononitrile (154 mg; 1 mmol) was added with constant stirring. The reaction mixture was refluxed for 3 h in the presence of a catalytic amount of piperidine. The reaction progress was monitored by TLC and after cooling, the formed precipitate was filtered off, washed with cold ethanol and dried under vacuum in a desiccator for 24 h. The solid was recrystallized from ethanol. Crystals suitable for X-ray crystallography were obtained by slow evaporation of a solution of the title compound in ethanol (yield 92%; m.p. 483 K).

S3. Refinement
The H atoms of the NH 2 group were were refined. The H atoms attached to the C atoms were positioned geometrically, with C-H = 0.95 Å and C-H = 1.00 Å for aromatic and methine H, respectively, and with U iso (H) = 1.2U eq (C).

Figure 1
View of the title compound with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.

Figure 2
View of the dimers formed by N-H···O hydrogen bonds.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.