Crystal structure of 2-{[1-(4-bromobenzyl)-1H-1,2,3-triazol-4-yl]methoxy}naphthalene-1,4-dione

In the title compound, C20H14BrN3O3, the benzene ring makes dihedral angles of 71.30 (11) and 68.95 (14)° with the naphthalene ring system and the triazole ring, respectively. The latter two ring systems are coplanar, with a dihedral angle of 2.92 (12)°. The O atoms deviate from the naphthalene ring system by 0.029 (2) and −0.051 (2) Å. In the crystal, molecules are linked by C—H⋯O and C—H⋯N hydrogen bonds, forming ribbons parallel to (10-1). The ribbons are linked via C—H⋯O and π–π stacking interactions [centroid–centroid distance = 3.4451 (14) Å], forming slabs parallel to the bc plane.


S1. Comment
Triazoles and triazole derivatives play an important role in pharmaceuticals, agrochemicals, dyes, photographic materials, and in corrosion inhibition and have many biological applications (Abu-Orabi et al., 1989;Demirbaş et al., 2002;Kritsanida et al., 2002. Naphthalene derivatives has been identified as new range of potent antimicrobials effective against wide range of human pathogens and have diverse and interesting antibiotic properties with minimum toxicity (Rokade & Sayyed, 2009;Upadhayaya et al. 2010).

S2. Experimental
The triazole appended lawsone was synthesized in a two step procedure. To a solution of lawsone (0.87 g, 5 mmol) in DMF (20 ml) was added potassium carbonate (1.04 g, 7.5 mmol) and the solution was stirred at room temperature.
Propargyl bromide (0.7 mL, 7.5 mmol) was added drop wise and the resulting mixture was allowed to stir overnight.
After completion of the reaction, in the mixture was partitioned between DCM and water, and the DCM layer was collected. The aqueous layer was extracted three times with DCM. The combined organic extracts were dried over anhydrous Na 2 SO 4 , and concentrated under vacuum to obtain the desired propargyllated lawsone that was later converted to a triazole using click chemistry. Propargyllated lawsone (0.636 g, 3 mmol) was dissolved in 1:1 THF / H 2 O mixture and triethyl amine (0.7 ml, 5 mmol), sodium azide (0.26 g, 4 mmol), 4-bromobenzyl bromide (0.68 mL, 4 mmol) and cuprous iodide (catalytic amount) were added to this solution. The resulting mixture was allowed to stir overnight at room temperature. Upon completion of the reaction, the mixture was filtered, extract with ethyl acetate, concentrated under vacuum and then subjected to column chromatography to obtain the desired product. The overall yield was 0.61 g (60%). Colourless block-like crystals were obtained on slow evaporation of the solvent.

S3. Refinement
The C-bound H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and allowed to ride on their parent atoms with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A partial view along the c axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1 for details).

Figure 3
A perspective view along the c axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1 for details; H atoms not involved in these interactions have been omitted for clarity).

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.