(E)-3-(3,5-Dimethoxyphenyl)-1-(1-hydroxynaphthalen-2-yl)prop-2-en-1-one

In the title molecule, C21H18O4, the C=C bond of the central enone group adopts a trans conformation. The dihedral angle formed by the naphthalene ring system and the benzene ring is 2.97 (11)°. The hydroxy group is involved in an intramolecular O—H⋯O hydrogen bond. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into chains along [001].


Related literature
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LH5555). Chalcones are one of the secondary metabolites in plants and belong to a flavonoid class with a C6-C3-C6 skeleton and C3 skeleton which is an α,β-unsaturated carbonyl (enone) group. Because of their diverse biological activities including anticancer , anti-inflammatory (Bandgar et al., 2010), anti-tubercular (Hans et al., 2010), and antimicrobial (Sharma et al., 2012), various chlacones have been isolated from natural sources and syntheized. In continuation of our research to develop novel chalcone derivatives which show broad range of biological activities (Hwang et al., 2011) the title compound was synthesized and and its crystal structure was determined.
The molecular structure of the title compound is shown in Fig .1. The C2═C3 bond of the central enone group adopts a trans configuration. The dihedral angle formed by the naphthalene ring system and the benzene ring is 2.97 (11)°. The C1═O1 bond [1.242 (3) Å] is slightly longer than the standard value (Allen et al. 1987) as this group is involved in an intramolecular O-H···O hydrogen bond with the hydroxy group. In the crystal, weak C-H···O hydrogen bonds link the molecules into one-dimensional chains along [001] (Fig. 2). Examples of structures of substituted prop-2-en-1-one compounds have been published (Fadzillah et al., 2012;Jasinski et al., 2011).

Experimental
A solution of 1-hydroxy-2-acetonaphthone (186 mg, 1 mmol) and 3,5-dimethoxybenzaldehyde (166 mg, 1 mmol) was dissolved in 10 ml of ethanol and the temperature was adjusted to around 276-277K in an ice-bath. To the cooled reaction mixture was added 0.5 ml of 50% aqueous KOH solution, and the reaction mixture was stirred at room temperature for 24 h. This mixture was poured into iced water (20 ml) was acidified with 6 N HCl solution. The mixture was extracted with ethylacetate (3 × 20 ml) and the combined organic layers were dried under MgSO 4 . Filtration and evaporation of the filtrate gave a residue which was purified by flash chromatography to give the title compound (210 mg, 63%).
Recrystallization of the title compound in ethanol gave orange colored crystals (mp: 422-424K).

Refinement
H atoms were placed in calculated positions and refined as riding with C-H = 0.95-0.98Å, O-H = 0.84 Å and U iso (H) = 1.2 U eq (C) or U iso (H) = 1.5U eq (C methyl , O).

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.