2-(4H-1,3-Benzoxazin-2-yl)phenol

The title compound, C14H11NO2, features an essentially planar molecule, the r.m.s. deviation for the 17 non-H atoms being 0.035 Å. This conformation is stabilized by an intramolecular O—H⋯N hydrogen bond that results in the formation of an S(6) ring. In the crystal structure, methylene–hydroxy C—H⋯O contacts result in a supramolecular chain aligned along the b axis.

The title compound, C 14 H 11 NO 2 , features an essentially planar molecule, the r.m.s. deviation for the 17 non-H atoms being 0.035 Å . This conformation is stabilized by an intramolecular O-HÁ Á ÁN hydrogen bond that results in the formation of an S(6) ring. In the crystal structure, methylene-hydroxy C-HÁ Á ÁO contacts result in a supramolecular chain aligned along the b axis.
The use of the EPSRC X-ray crystallographic service at the University of Southampton, England and the valuable assistance of the staff there is gratefully acknowledged. JLW acknowledges support from CAPES (Brazil).
While the NMR spectra, in particular the two hydrogen singlet in the 1 H NMR spectrum, suggested the compound (2: R = H) confirmation from the X-ray structure determination was considered to be of value, particularly since treatment of 6-nitro-2-hydroxybenzaldehyde with NH 4 OAc in acetic acid had been reported to give 5 (Beer et al., 1948). However, no spectral details had been provided for 5. In the light of our findings, the structure of 5 could be modified to (2: R = NO 2 ).
The change from 5 to (2: R = NO 2 ) merely involves a prototropic rearrangement. Herein, the crystal and molecular structure of (I) [= 2: R = H in Fig. 1] is described.
The molecular structure of (I), Fig. 2, is essentially planar with the RMS for the 17 non-hydrogen atoms being 0.035 Å. The maximum deviation is 0.049 (1) Å for the N1 atom. This conformation is stabilized by an intramolecular O-H···N hydrogen bond that completes an S(6) ring synthon. The most prominent interactions in the crystal structure are of the type C-H···O, Table 1, which lead to supramolecular chains along the b direction, Fig. 3.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.95-0.99 Å) and refined as riding with U iso (H) = 1.2U eq (C). The hydroxyl-H was located from a difference map and refined with O-H = 0.840±0.001 Å, and with U iso (H) = 1.5U eq (O). Fig. 1. Reaction products.

Fig. 2. Molecular structure of (I) showing the intramolecular O-H···N hydrogen bonding (orange dashed lines)
, the atom-labelling scheme, and displacement ellipsoids at the 50% probability level.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes.