Methyl 2-amino-5-chlorobenzoate

The title compound, C8H8ClNO2, is almost planar, with an r.m.s. deviation of 0.0410 Å from the plane through the non-hydrogen atoms. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link the molecules into chains along the b axis. An intramolecular N—H⋯O hydrogen bond results in the formation of a six-membered ring.


Comment
Quinazolinones play an important role in the fields of natural products and medicinal chemistry. The title compound, methyl 2-amino-5-chlorobenzoate, (I), is a useful pharmaceutical intermediate (Dong et al. 2009). The molecule of (I) (Figure 1.) is almost planar (except the methyl hydrogens) with r. m. s. deviation of 0.0410 Å and the bond lengths (Allen et al., 1987) and angles are within normal ranges. The intramolecular N-H···O hydrogen bond (Table 1) results in the formation of a six-membered ring (C1/C6/C7/O2/H0B/N). In the crystal structure, intermolecular N-H0A···O2 hydrogen bonds link the molecules to form a stable structure (Table 1. and Figure 2.).

Experimental
The title compound, methyl 2-amino-5-chlorobenzoate was prepared by the literature method (Dong et al., 2009). To a solution of 2-aminobenzoic acid (10 g, 66 mmol) in DMF (40 mL) was added N-halosuccinimide (66 mmol) and the reaction mixture was heated at 100 °C for 40 min, cooled to room temperature, left stand overnight, and then slowly poured into ice-water (150 mL) to precipitate a white solid. The solid was filtered, washed with water (50 mL * 3), then taken up in ethyl acetate (600 mL). The ethyl acetate solution was dried over magnesium sulfate, evaporated under reduced pressure and the residual solid was washed with ether (30 mL * 3) to afford intermediate 2-amino-5-chlorobenzoic acid. To an alcohol solution (60 mL) containing 2-amino-5-chlorobenzoic acid (20 mmol) was added thionyl chloride (60 mmol), and the resulting suspension was refluxed overnight. The solvent was evaporated followed by addition of EtOAc, washed with 10% NaOH solution, dried, filtered, and evaporated to afford the desired anthranilic acid esters methyl 2-amino-5-chlorobenzoate.
Crystals suitable for X-ray analysis were obtained by slow evaporation of an methanol solution.

Refinement
H atoms were positioned geometrically, with N-H = 0.86 Å (for NH 2 ) and C-H = 0.93, 0.98 and 0.96 Å for aromatic, methine and methyl H, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C,N), where x = 1.5 for methyl H and x = 1.2 for all other H atoms. Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq