Crystal structure of methyl (E)-4-[2-(8-hydroxyquinolin-2-yl)vinyl]benzoate

The title 8-hydroxyquinoline derivative has an E conformation about the C=C bond, and the quinoline ring system and the benzene ring are inclined to one another by 29.22 (7)°.

The title compound, C 19 H 15 NO 3 , was synthesized by a Perkin reaction of 2-methyl-8-hydroxyquinoline and 4-formyl-2-methylbenzoate in acetic anhydride under a nitrogen atmosphere. The molecule has an E conformation about the C C bond, and the quinoline ring system and the benzene ring are inclined to one another by 29.22 (7) . There is an intramolecular O-HÁ Á ÁN hydrogen bond in the 8-hydroxyquinoline moiety. In the crystal, molecules are linked by pairs of O-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (28) ring motif. The dimers are linked by C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions, forming sheets parallel to plane (101).

Chemical context
In recent years, 8-hydroxyquinoline and its derivatives have played an important role in coordination chemistry (Albrecht et al., 2008;Cacciatore et al., 2013), shown to exhibit biological activity (du Moulinet d' Hardemare et al., 2012) and have found various applications in the fields of synthetic chemistry (Song et al., 2006) and organic light-emitting diodes, which have been extensively exploited in the synthesis of luminescent metal complexes (Tang et al., 1987). It is therefore highly desirable to develop new efficient 8-hydroxyquinoline derivatives for use in luminescent metal complexes. In the present work, we report on the synthesis and crystal structure of a new 8-hydroxyquinoline derivative, synthesized by the Perkin reaction of 2-methyl-8-hydroxyquinoline and 4-formyl-2methylbenzoate.

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. It contains an 8-hydroxyquinoline moiety, with an intramolecular O-HÁ Á ÁN hydrogen bond ( Fig. 1 and Table 1), ISSN 2056-9890 and a methylbenzoate unit. They are linked by the C9 C10 bond [1.321 (2) Å ] with an E conformation. The C11-C10 and C6-C9 bond lengths are 1.463 (2) and 1.466 (2) Å , respectively. These distances are shorter than the standard length of a C-C single bond (ca 1.5 Å ) because of the conjugate system formed by the C9 C10 bond and the aromatic systems. The quinoline ring system and the benzene ring are inclined to one another by 29.22 (7) .

Supramolecular features
In the crystal, molecules are linked by pairs of O-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (28) ring motif (Table 1 and Fig. 2). The dimers are linked by C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions, forming sheets parallel to (101); see Table 1

Figure 3
A view along the b axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1) and, for clarity, only H atoms H3O and H5A are included.

Figure 1
View of the molecular structure of the title compound, showing the atom labelling and 40% probability displacement ellipsoids. The intramolecular O-HÁ Á ÁN hydrogen bond is shown as a dashed line (see Table 1). Table 1 Hydrogen-bond geometry (Å , ).

Synthesis and crystallization
The title compound was prepared following reported procedures (Jing et al., 2006;Yuan et al., 2012). A mixture of 2-methy-8-hydroxyquinoline (1.59 g, 10 mmol), 4-formyl-2methylbenzoate (1.64 g, 10 mmol) and acetic anhydride (20 ml) was stirred for 12 h at 423 K under a nitrogen atmosphere. After cooling it was poured into ice-water (150 ml) and stirred for 1-2 h. Then, the puce solid obtained was filtered and together with triethylamine (1 g, 10 mmol) was dissolved in DMF (30 ml) and the mixture stirred for 3 h at 408 K. After cooling, the reaction mixture was concentrated and purified by chromatography on silica gel (petroleum ether/EtOAc = 3/1). The product obtained was dissolved in ethanol, and on slow evaporation of the solvent yellow crystals were obtained within 2 weeks.

Methyl (E)-4-[2-(8-hydroxyquinolin-2-yl)vinyl]benzoate
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.