2-Hydroxy-N′-[2-(6-methoxynaphthalen-2-yl)propanoyl]benzohydrazide

In the title compound, C21H20N2O4, the naphthalene ring system makes a dihedral angle of 84.5 (3)° with the benzene ring, and the –C(=O)–N(H)–N(H)–C(=O)– torsion angle is 70.7 (7)°, so that the molecule is twisted. An S(6) ring motif is formed via an intramolecular O—H⋯O hydrogen bond. In the crystal, molecules are linked by N—H⋯O and C–H⋯O hydrogen bonds into supramolecular layers in the ab plane.

An intramolecular O-H···O hydrogen bond which generates an S(6) ring motif (Etter et al., 1990) is observed in the molecular structure (Table 1). The crystal structure is stabilized by intermolecular N-H···O and C-H···O hydrogen bonds (Table 1, Fig. 2) which connect molecules into supramolecular layers in the ab plane.

Experimental
A mixture of 0.01 mol of 2-(6-methoxy-2-naphthyl)propanoyl chloride and 0.01 mol 2-hydroxybenzohydrazide in tetrahydrofuran was heated at 339 K for three hours. The reaction progress was monitored by TLC until completed. The mixture was then poured on cold water to afford the solid product which was filtered off, dried and recrystallized from ethanol in 72% yield with M.pt: at 482-484 K. Suitable crystals for X-ray diffraction were obtained by slow evaporation of a diluted ethanolic solution of the product over two days.

Refinement
The hydroxyl-and amide-H atoms were located in difference density maps, and were refined with the (O, N)-H distance restraints of 0.82 (2) Å and 0.86 (2) Å, respectively, and with free U iso . The remaining H atoms were positioned geometrically and refined using a riding model with C-H = 0.93, 0.96 and 0.98 Å for aromatic-, methyl-and methine-H, respectively, with U iso (H) = 1.2 or 1.5 U eq (C).
The crystal used was very small (0.01 x 0.05 x 0.14) but was the best available after repeated recrystallizations. As such a reasonable number of the higher angle diffractions were indistinguishable from the background noise. The crystal was exposed to the X-rays for as long as required until reached a level where increasing the exposure did not result in the observation of further high angle data. From the reflections collected the structure could be readily determined, such that hydrogen atom positions could be seen in the difference map, even though most were later fixed using standard riding positions (the OH and NH hydrogen atoms were allowed some freedom of position whilst restraining their distances to supplementary materials sup-2 Acta Cryst. (2012). E68, o1251-o1252 0.82 Å and 0.86 Å, respectively). In the absence of significant anomalous scattering, 1052 Friedel pairs were averaged.
One poorly fitted reflection (0 1 1) was omitted from the refinement.

Figure 1
The molecular structure of (I), showing the labelling of the non-H atoms and displacement ellipsoids drawn at the 50% probability level.  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.