4-[4-(1H-Tetrazol-5-yl)phenoxy]benzaldehyde

The asymmetric unit of the title compound, C14H10N4O2, contains two independent molecules with similar structures. In one molecule, the tetrazole ring is oriented at dihedral angles of 17.71 (16) and 57.13 (17)°, respectively, to the central benzene ring and the terminal benzene ring; in the other molecule, the corresponding dihedral angles are 16.46 (18) and 75.87 (18)°. Intermolecular N—H⋯N hydrogen bonds and weak C—H⋯O and C—H⋯N hydrogen bonds occur in the crystal structure.


Comment
Tetrazoles play a variety of roles in coordination chemistry, medicinal chemistry, materials chemistry etc. (Ostrovskii et al., 2008). We intended to find a new way for preparation of tetrazoles using a new solid acid which is regarded as a green catalyst. In order to confirm the verity of the final product, the single crystal X-ray analysis was performed and the structure is reported here.

Experimental
A solution of 4-(4-formylphenoxy)benzonitrile (892 mg, 4 mmol) and sodium azide (780 mg, 12 mmol) in dry DMF (15 mL) at the presence of sulfuric acid on silica gel (5% load, 400 mg ) was heated to 80°C. When the reaction was completed, the solid acid was filtered, 2 mL water was added to the filtration, and then was extracted with ethyl acetate (20 mL × 3). The ethyl acetate layers were combined and washed by 20 mL water, and then 15 mL saturated sodium chloride and dried over anhydrous sodium sulfate. The solution was evaporated and the residue was separated on silica gel column chromatography with a gradient of petroleum ether and ethyl acetate as eluent to yield 570 mg the title compound. The compound was then dissolved in methanol, and colorless crystals were formed on slow evaporation at room temperature over one week.

Refinement
The H1N and H2N atoms were located in a difference Fourier map and refined isotropically. Other H atoms were placed in calculated positions with C-H = 0.93 Å and refined using a riding model with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

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.