Methyl 4-amino-3-methoxyisoxazole-5-carboxylate

The crystal structure of the title compound obtained from the reduction of its nitro precursor, methyl 3-methoxy-4-nitroisoxazole-5-carboxylate, is described.

The title compound, C 6 H 8 N 2 O 4 , a new derivative of isoxazole, has been synthesized and structurally characterized.The crystal structure shows the molecule to be almost planar (r.m.s.deviation for the non-hydrogen atoms = 0.029 A ˚), this conformation being supported by an intramolecular N-HÁ Á ÁO hydrogen bond.In the extended structure, the molecules are linked by N-HÁ Á ÁO hydrogen bonds into chains propagating along [010].

Structure description
Isoxazoles, five-membered heterocyclic compounds containing adjacent nitrogen and oxygen atoms, have many applications including in photochromic components (Pu et al., 2011), liquid crystals (Kauhanka et al., 2006), solar cells (Yoon et al., 2022), high energy materials (Lal et al., 2023), pesticides and insecticides (Wang et al., 2022) and pharmaceuticals (Zhu et al., 2018).In a continuation of our previous work on isoxazole derivatives (Abdul Manan et al., 2023), we now present the synthesis and structure of the title compound.
In the crystal of the title compound, adjacent molecules are linked by N-HÁ Á ÁO c (c = carbonyl) and N-HÁ Á ÁO i (i = isoxazole) hydrogen bonds, forming an R 2 2 (7) loop, which generates chains of molecules running along the crystallographic b-axis direction (Fig. 2).No additional directional interactions exist between chains.This combination of hydrogen bonds leading to chain formation is not seen in related isoxazole compounds as a result of the different relative position of the amine group on the isoxazole ring.While the combination of two inter-and one intramolecular hydrogen bond has been seen previously in related isoxazoles (Sony et al., 2005;Regiec et al., 2018;Ba ˛chor et al., 2019), the pattern of hydrogen bonds is either different or has additional hydrogen bonds contributing to it, and the resulting supramolecular motifs differ as well.One-dimensional chain motifs have been seen in two of the related isoxazoles (Schmitt et al., 2015(Schmitt et al., , 2017)), although the pattern of hydrogen bonds that leads to the chains is different.

Figure 1
The molecular structure of the title compound, showing displacement ellipsoids drawn at the 50% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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.

data reports data-2
IUCrData (2023).8, x230623 Refinement.Refinement was performed using all reflections.The weighted R-factor (wR) and goodness of fit (S) are based on F 2 .R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 sigma(F 2 ) is used only for calculating Rfactor (gt).Carbon-bound H atoms were included in calculated positions (C-H = 0.98 Å) and refined as riding atoms with U iso (H) = 1.2U eq (C).The nitrogen-bound hydrogen atoms were located from difference Fourier maps and refined isotropically subject to a distance restraint.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å

Figure 2
Figure 2 View down the [101] axis of the [010] chain formed by N-HÁ Á ÁO hydrogen bonds, which are shown as dashed lines.

Table 2
Experimental details.