5-Methyl-N-(1,3-thiazol-2-yl)isoxazole-4-carboxamide

In the title compound, C8H7N3O2S, the dihedral angle between the thiazol and isoxazole rings is 34.08 (13)°. In the crystal, the molecules are linked by pairs of N—H⋯N hydrogen bonds, forming inversion dimers, and C—H⋯O interactions, resulting in chains along the b-axis direction.

In the title compound, C 8 H 7 N 3 O 2 S, the dihedral angle between the thiazol and isoxazole rings is 34.08 (13) . In the crystal, the molecules are linked by pairs of N-HÁ Á ÁN hydrogen bonds, forming inversion dimers, and C-HÁ Á ÁO interactions, resulting in chains along the b-axis direction.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2631). Leflunomide is one of the most effective isoxazole-containing disease-modifying drugs for treating rheumatoid arthritis (Shaw et al., 2011;Schattenkirchner, 2000). Many leflunomide analogs have been synthesized which exhibit potent immunomodulating effect (Huang et al., 2003). In our previous work, some anolog has been sucessfully sythesized (Wang et al., 2011). A new leflunomide analog, N-5-methyl-N-(thiazol-2-yl)isoxazole-4-carboxamide, was synthesized in our laboratory as a novel and potent immunomodulating drug. In this paper we report its crystal structure.
The bond distances and angles in the title compound ( Fig. 1) agree very well with the corresponding bond distances and angles reported in a closely related compound (Wang et al., 2011). The dihedral angle between the C1/C2/N1/C3/S thiazol ring and the C5/C6/N3/O2/C7 isoxazole ring is 34.08 (13)

Refinement
All H atoms were placed geometrically at the distances of 0.93-0.96 Å for C-H and 0.86 Å for N-H and included in the refinement in riding motion approximation with U iso (H) = 1.2 or 1.5U eq of the carrier atom.

Figure 2
A view of the N-H···N and C-H···O hydrogen bonds (dotted lines) in the crystal structure of the title compound. H atoms non-participating in hydrogen-bonding were omitted for clarity. 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 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.