tert-Butyl 2-(3-acetylamino-2-oxo-1,2-dihydro-1-pyridyl)acetate

The title compound, C13H18N2O4, crystallizes as discrete molecules associated as N—H⋯O hydrogen-bonded dimers disposed about a crystallographic inversion centre. The structure is the first solid-state structure for a 3-acetylpyridone without C-4 to C-6 substituents. The amide subsituent at C-3 is coplanar with the pyridone ring, while the tert-butyl ester group is orthogonal to the pyridine ring. The amide and ester carbonyl O atoms are not involved in strong hydrogen bonding with only a number of intramolecular and intermolecular C—H⋯O interactions apparent in the structure.

The title compound, C 13 H 18 N 2 O 4 , crystallizes as discrete molecules associated as N-HÁ Á ÁO hydrogen-bonded dimers disposed about a crystallographic inversion centre. The structure is the first solid-state structure for a 3-acetylpyridone without C-4 to C-6 substituents. The amide subsituent at C-3 is coplanar with the pyridone ring, while the tert-butyl ester group is orthogonal to the pyridine ring. The amide and ester carbonyl O atoms are not involved in strong hydrogen bonding with only a number of intramolecular and intermolecular C-HÁ Á ÁO interactions apparent in the structure.
Similiarly, other enzyme-ligand interactions have been observed in the solid state with kinases; a N1-aryl pyridone with Met kinase (Kim et al., 2008) and a N1-aryl C3-aryl pyridone with KDR kinase (Hu et al., 2008). Thus an understanding of the structure of substituted pyridone compounds is important. Elsewhere, the facile synthesis of N1, C3-substituted pyridones is reported (Karis et al., 2007). Herein we report the first solid state structure (II) for a 3-acetylpyridone without C4 to C6 substituents.
For the preparation of compound (II), compound (I) (0.78 g, 3.48 mmol) was dissolved in a mixture of dry dichloromethane (10 ml) and triethylamine (0.97 ml, 6.96 mmol) under nitrogen. Acetyl chloride (0.50 ml, 6.96 mmol) was added dropwise at 295 K. The resulting mixture was stirred for 4 h and then concentrated to give a suspension of the product and triethylamine hydrochloride. The suspension was directly transferred to a silica gel column using dichloromethane with 0.5% triethylamine and eluted with an ethyl acetate /dichloromethane gradient (0 to 20% ethyl acetate, with 0.5% triethyl amine. Red crystals of (II) (m.p. 415-418 K) (0.91 g, 98%) were isolated by slow evaporation from an ethyl acetate /dichloromethane solution.

Refinement
Carbon bonded H atoms were included in idealized positions and refined as riding atoms, with C-H set to 0.95-0.96 Å.
U iso (H) values were set to 1.2U eq (aromatic, methylene) and 1.5U eq (methyl) of the parent atom. The amide proton was located from difference Fourier maps and refined with N-H set to 0.86Å and U iso (H) values set to 1.2U eq of the parent atom. Considerable thermal motion was apparent in the peripheral carbons of the tert-butyl group. Fig. 1. View of the molecular structure of (II) with the atom numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radii.  tert-Butyl 2-(3-acetylamino-2-oxo-1,2-dihydro-1-pyridyl)acetate
Stationary background counts were recorded at each end of the scan, and the scan time:background time ratio was 2:1.
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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. supplementary materials sup-9