Ethyl ( 3-nitro-2-oxo-1 , 2-dihydropyridin-1-yl ) acetate

# 2006 International Union of Crystallography All rights reserved The title compound, C9H10N2O5, crystallizes with two crystallographically independent molecules in the asymmetric unit. In the crystal structure, the nitropyridone rings are connected by weak C—H O interactions, forming sheet-like arrays, which are in turn linked by C—H and – interactions between the nitropyridone rings on one side, and by C— H O and van der Waals interactions between the ester groups on the other.

The title compound, C 9 H 10 N 2 O 5 , crystallizes with two crystallographically independent molecules in the asymmetric unit. In the crystal structure, the nitropyridone rings are connected by weak C-HÁ Á ÁO interactions, forming sheet-like arrays, which are in turn linked by C-HÁ Á Á andinteractions between the nitropyridone rings on one side, and by C-HÁ Á ÁO and van der Waals interactions between the ester groups on the other.

Comment
Pyridones can act as a P3 to P2 conformational restraint in the design of inhibitors of serine protease enzymes (Loughlin et al., 2004). This is often facilitated by the presence of a 3-amino group, which acts as a hydrogen-bonding site. Typically, 3nitropyrid-2-ones (I) and (II) are used as synthetic precursors to 3-aminopyrid-2-ones (Breslin et al., 2003;Huang et al., 2003;Reiner et al., 2002;Warner et al., 1994). Compound (II) lacks the hydrogen-bonding site at the 3 position and solid-state structures for 3-nitropyridones (without C4 to C6 substituents) are restricted to a report of the complex of (I) with 2amino-5-nitropyridine (Velikova et al., 1997). Here, we report the first solid-state structure of the title compound, (II). Compound (II) was prepared by N-alkylation of (I) with sodium hydride and ethyl bromoacetate, as reported elsewhere (Warner et al., 1994;Breslin et al., 2003).
In the crystal structure, the nitropyridone rings are connected by weak C-HÁ Á ÁO interactions between the aromatic and aliphatic H atoms and the carbonyl and nitro group O atoms, forming sheet-like arrays in the bc plane. These sheets are in turn linked together by C-HÁ Á Á andinteractions between the nitropyridone rings on one side, and by C-HÁ Á ÁO and van der Waals interactions between the ester groups on the other (Fig. 2).

Experimental
Sodium hydride (1.38 g, 57.8 mmol) was added in portions over a period of 30 min to compound (I) (6.75 g, 48.2 mmol) in dry tetrahydrofuran (100 ml). The resulting suspension was stirred for 30 min. Ethyl bromoacetate (5.86 ml, 53.0 mmol) was added dropwise over a period of 30 min. The resulting yellow suspension was heated to 328 K under nitrogen for 24 h. The red reaction mixture was filtered and the solid thoroughly washed with ethyl acetate. The filtrate was concentrated under reduced pressure and the resulting red oil purified by silica-gel column chromatography (ethyl acetate-dichloromethane gradient from 0-40% ethyl acetate, with 0.4% triethylamine). Pale-yellow crystals of compound (II) (m.p. 327-329 K; yield 10.7 g, 98%) were isolated by slow evaporation of an ethyl acetate solution of (II )/3 (Á/) max = 0.010 Á max = 0.17 e Å À3 Á min = À0.18 e Å À3 Table 1 Selected geometric parameters (Å , ). A view of one of the two independent molecules of (II), with the atomnumbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
H atoms were constrained as riding atoms, with C-H = 0.95 Å , and with U iso (H) = 1.2U eq (C).