4-[(2-Hydroxy-1-naphthyl)(piperidin-1-yl)methyl]benzonitrile

In the title compound, C23H22N2O, obtained from the condensation reaction of 4-formylbenzonitrile, 2-naphthol and piperidine, the dihedral angle between the naphthalene ring system and the benzene ring is 75.31 (4)°. The piperidine ring adopts a chair conformation. The crystal structure is stabilized by intermolecular C—H⋯N hydrogen bonds, which link the molecules into centrosymmetric dimers. An intramolecular O—H⋯N hydrogen bond is also present.

In the title compound, C 23 H 22 N 2 O, obtained from the condensation reaction of 4-formylbenzonitrile, 2-naphthol and piperidine, the dihedral angle between the naphthalene ring system and the benzene ring is 75.31 (4) . The piperidine ring adopts a chair conformation. The crystal structure is stabilized by intermolecular C-HÁ Á ÁN hydrogen bonds, which link the molecules into centrosymmetric dimers. An intramolecular O-HÁ Á ÁN hydrogen bond is also present.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Over one hundred years ago, Betti developed a straightforward synthesis involving the condensation of 2-naphthol, ammonia and equivalents of benzaldehyde, followed by the addition of HCl and KOH to yield 1-(a-aminobenzyl)-2-naphthol. This product which possesses an asymmetric carbon center is known as a Betti base (Zhao & Li et al. 2004). Betti-type reaction is an important method to synthesize chiral ligands and by this method many unnatural homochiral amino-phenol compounds have been obtained (Lu et al. 2002;Xu et al. 2004;Wang et al. 2005). Here we report the synthesis and crystal structure of the title compound, 4-[(2-hydroxy-1-naphthyl)(1-piperidinyl)methyl]benzonitrile (Fig. 1).
The naphthalene (A; C1-C10), benzene (B; C12-C17) and piperidine (C; N2/C19-C23) rings are planar and the dihedral angles between A/B, A/C, and B/C are 75.31 (4)°, 67.24 (5)°, and 88.80 (5)°, respectively. The crystal structure (Fig. 2) is stabilized by intermolecular C-H···N hydrogen bonds between an H atom of benzene ring and the N atom of the nitrile group, with a C14-H14···N1i (Table 1 and Fig. 2), which link the molecules into centrosymmetric dimers. In addition, the crystal structure exhibits an intramolecular O-H···N hydrogen bond, with a O1-H1···N2 (Table 1 and   without solvent under nitrogen. The temperature was raised to 120°C in one hour gradually and the mixture was stirred at this temperature for 10 h. The system was treated with 20 ml of ethanol 95% and cooled. The precipitate was filtered and washed with a small amount of ethanol 95%. The title compound was isolated using column chromatography (Petroleum ether: ethyl acetate-4:1). Single crystals suitable for X-ray diffraction analysis were obtained from slow evaporation of a solution of the title compound in ethyl acetate at room temperature.

Refinement
H atoms bonded to O atoms were located in a difference map and refined freely. Other H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.97 Å and U iso (H) = 1.3-1.6U eq (C).

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.