5-(4-Fluorophenyl)-4-(4-pyridyl)-1,3-oxazol-2-amine

In the crystal structure of the title compound, C14H10FN3O, the plane of the isoxazole ring makes dihedral angles of 35.72 (9) and 30.00 (9)°, respectively, with those of the 4-fluorophenyl and pyridine rings. The plane of the 4-fluorophenyl ring makes a dihedral angle of 45.85 (8)° with that of the pyridine ring. The crystal structure is stabilized by intermolecular N—H⋯N hydrogen bonding. The two types of hydrogen bonds result in two chains, extending along the a axis, which are related by centres of symmetry.

In the crystal structure of the title compound, the isoxazole ring makes dihedral angles of 35.72 (9)° and 30.00 (9)° to the 4-fluorophenyl ring and the pyridine ring, respectively ( Figure 1). The 4-fluorophenyl ring makes dihedral angles of 45.85 (8)° to the pyridine ring.
The crystal packing ( Figure 2) shows that the amino function acts an a hydrogen bond donor forming hydrogen bonds to the nitrogen atom of the pyridine ring and to the nitrogen atom of the oxale ring of two different molecules. The lenght of the hydrogen bonds is 1.99 Å and 2.03 Å, respectively ( Table 1). The two types of hydrogen bonds result in two chains that elongate along the a-axis which are related by centres of symmetry. DMF (1 ml) were combined in a reaction vial. The reaction vessel was heated in a CEM microwave reactor for 10 min at 433 K (initial power 250 W) and afterwards the vessel was cooled down to room temperature by a stream of compressed air.
Water and ethyl acetate were added and the organic layer was separated. This layer was washed with water (3x), dried over Na 2 SO 4 and concentrated in vacuo. The yellow residue was suspended twice with DCM/EtOH 95-5, filtered and finally dried. Yield 83 mg (81 %). Suitable crystals of the title compound for X-ray were obtained by slow evaporation at 298 K of a solution of methanol.

Refinement
Hydrogen atoms attached to carbons were placed at calculated positions with C-H = 0.95 Å (aromatic) or 0.98-0.99 Å (sp 3 C-atom). The H atoms attached to N1 were located in diff. Fourier maps. All H atoms were refined in the riding-model approximation with isotropic displacement parameters (set at 1.2-1.5 times of the U eq of the parent atom).

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.