N′-[(E)-Benzylidene]-2-(6-methoxynaphthalen-2-yl)propanohydrazide

The title molecule, C21H20N2O2, exists in the solid state in the ‘extended’ form. The crystal packing consists of ribbons of molecules extending parallel to c and associated via N—H⋯O and weak C—H⋯O hydrogen bonds. C—H⋯π interactions are also present.

The title molecule, C 21 H 20 N 2 O 2 , exists in the solid state in the 'extended' form. The crystal packing consists of ribbons of molecules extending parallel to c and associated via N-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds. C-HÁ Á Á interactions are also present. H atoms treated by a mixture of independent and constrained refinement Á max = 0.34 e Å À3 Á min = À0.26 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).

Comment
Anti-inflammatory drugs are widely prescribed in clinical practice to treat a broad range of diseases associated with inflammatory processes (Merlet et al., 2013). Naproxen, (S)-(+)-6-methoxy-a-methyl-2-naphthaleneacetic acid, is a nonsteroidal anti-inflammatory drug used in painful inflammatory rheumatic and certain non-rheumatic conditions (Khanna et al., 2006;Bhaduri et al., 1995;Dharmani et al., 2004). As with other common non-steroidal anti-inflammatory drugs (NSAIDs), Naproxen has been reported to be associated with a number of undesirable effects, which in particular include gastrointestinal (GI) toxicity (Neeraj et al., 2010). These reports confirm that gastrointestinal side-effects are due to the presence of a free carboxylic group (Asif 2009). Therefore, temporary masking or manipulation of the acidic group in NSAIDs are promising means to reduce or to abolish the GI toxicity due to the local action mechanism (Parmeshwari et al., 2009). Based on such facts, the title compound has been prepared.
In the crystal structure, the molecules exist in the "extended" form. The packing consists of ribbons of molecules extending parallel to c (Fig. 2) and associated via N-H···O and weak C-H···O hydrogen bonds (Table 1 and Fig. 3). In addition, C-H···p interactions are observed (Table 1).

Experimental
A mixture of 244 mg (1 mmol) of 2-(6-methoxynaphthalen-2-yl)propanehydrazide and benzaldehyde 106 mg (1 mmol) in 30 ml ethanol with few drops of glacial acetic acid as a catalyst was refluxed for 5 h. After the reaction mixture was cooled to ambient temperature, the excess solvent was evaporated under vacuum and the resulting solid product was filtered off, washed with cold ethanol and recrystallized from ethanol to afford high quality, clear colourless blocks (M.p. 453 -455 K) in a good yield 79%..

Refinement
The amino H atom was located in a difference Fourier map and was refined with U iso (H) = 1.2U eq (N). C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms with C-H = 0.95 -1.00 Å, with U iso (H) = 1.2 or 1.5U iso (C).  Perspective view of the title molecule with 50% probability displacement ellipsoids.

Figure 2
The hydrogen bonding (dotted lines) viewed along the a axis of the title compound.  Packing viewed along the c axis showing the ribbon like structure with intra-ribbon C-H···O hydrogen bonds.

N′-[(E)-Benzylidene]-2-(6-methoxynaphthalen-2-yl)propanohydrazide
Crystal data C 21 H 20 N 2 O 2 M r = 332.39 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 10.3754 (17)  Special details Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 25 sec/frame. 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.