3-[2-(3-Methylquinoxalin-2-yloxy)ethyl]-1,3-oxazolidin-2-one

Two isomers were isolated during the reaction between 3-methylquinoxalin-2-one and bis(2-chloroethyl)amine hydrochloride. The crystal structure of one isomer has already been reported [Caleb, Bouhfid, Essassi & El Ammari (2009). Acta Cryst. E65, o2024–o2025], while that of the second isomer is the subject of this work. The title compound, C14H15N3O3, has a new structure containing oxazolidine and quinoxaline rings linked by an ethoxy group. The main difference between the two isomers is the position of the oxazolidine group with respect to the quinoxaline system. The dihedral angle between the fused planar rings and the oxazolidin-2-one ring is 41.63 (8)° in the title molecule.

The structure of the 3-(2-(3-methyl-1,2-dihydro-quinoxalin-2-yloxy)ethoxy) oxazolidin-2-one molecule is also built up from two fused six-membered rings linked to a five-membered ring (oxazolidin-2-one) by an ethoxy group, as shown in Fig.1. It would be interesting to compare the crystal structures of both isomers of this compound (scheme 1). Actually, the geometric parameters (bond lenghths and angles) of the two isomers are very similar to those observed in other heterocyclic structures (Aschwanden et al., 1976;Doubia et al., 2007;Mamedov et al., 2007). However, the main difference between the two isomers is the position of the oxazolidine group with respect to the quinoxalin. Moreover, the dihedral angle between the fused six-membered rings and the five cycles measuring 20.04 (9)° in the isomer 1 instead of 41.63 (8)° in the isomer 2.

Experimental
In a 100 ml flask, is reacted 0.0125 moles of quinoxalin-2-one with 2.66 moles of dichloroethylamine hydrochloride in 40 ml of dimethyl formamide in presence of 2.87 moles of potassium carbonate and a few milligrams of tetran-butyl ammonium bromide. The mixture was brought to reflux in a sand bath, magnetic stirring and the reaction progress was monitored by thin layer chromatography. After evaporation of solvent under reduced pressure, the residue obtained is chromatographed on silica column (hexane / acetate: 4 / 6). Thus we have isolated two compounds. Recrystallization occurred in the same eluent. This compound was obtained in 38% and his melting point is 169°C.

Refinement
H atoms were located in a difference map and treated as riding with C-H = 0.96 Å for methyl groups and C-H = 0.93 Å for all other hydrogens with U iso (H) = 1.2 U eq (aromatic, methine ) or U iso (H) = 1.5 U eq (methyl). All other H atoms were located from difference Fourier maps and refined without any distance restraints.

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 > σ(F 2 ) is used only for calculating Rfactors(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.