Synthesis, crystal structure and Hirshfeld surface analysis of (3Z)-4-[(4-amino-1,2,5-oxadiazol-3-yl)amino]-3-bromo-1,1,1-trifluorobut-3-en-2-one

In the crystal, molecular pairs are connected by N—H⋯N hydrogen bonds, forming dimers with an (8) motif. The dimers are linked into layers parallel to the (10 ) plane by N—H⋯O hydrogen bonds. In addition, C—O⋯π and C—Br⋯π interactions connect the molecules, forming a three-dimensional network.


Chemical context
Among the main trends in the development of organic chemistry over the past 20 years, one can note the key role and rapid development of the chemistry of organofluorine compounds (Meanwell, 2018).This is due to the extremely high practical importance of organofluorine molecules.The introduction of fluorine into the target molecule changes such important parameters as lipophilicity, solubility, binding to receptors, metabolism, acid-base characteristics, and conformational properties of compounds.Currently, about 25% of new drugs and 35% of substances used in agriculture (agrochemicals) contain at least one fluorine atom (Chandra et al., 2023;Han et al., 2020;Mei et al., 2019;Shabir et al., 2023;Zhang et al.,, 2022).
Diaminofurazanes and their derivatives are widely used to obtain useful heterocyclic compounds, high-energy explosives with great potential application value, antimicrobials, highly effective biocidal and antitumor agents, as well as in photochemistry (Chang et al., 2023;Chen et al., 2022;Dutta et al., 2022;Liao et al., 2020;Liu et al., 2022;Ugrak et al., 2023).Similarly to other N-ligands (Gurbanov et al., 2022a,b;Kopylovich et al., 2011aKopylovich et al., ,b, 2012)), new derivatives of furazan can also be used in crystal engineering (Gurbanov et al., 2020) as well as the synthesis of coordination compounds for catalysis (Mac Leod et al., 2012;Mahmudov et al., 2013;Mizar et al., 2012) and biological studies (Martins et al., 2017).In fact, the non-covalent bond-acceptor ability of the furazan motif can be employed as a unique tool for crystal engineering.We believe that the combination of trifluoromethyl and furazan fragments in one molecule can lead to the synthesis of new compounds with useful properties.Therefore, we studied the condensation of (Z)-3-bromo-4-ethoxy-1,1,1-trifluorobut-3-en-2-one with diaminofurazan in different polar solvents, with the best yield being in ethanol.It was shown that the reaction occurs only with the participation of the vinyl fragment and the active ketone group is not affected.The condensation product is an enamine, and its structure was confirmed by NMR spectroscopy and X-ray diffraction analysis.
In the crystals of I and II, C-H� � �� interactions are observed between neighboring molecules.In the crystal of III, one of the amino H atoms forms an intramolecular N-H� � �N hydrogen bond; adjacent molecules are linked by N-H� � �N hydrogen bonds, forming a chain running along [102].In the crystal of IV, intermolecular N-H� � �N, N-H� � �O, O-H� � �N and O-H� � �O hydrogen bonds link the molecules into a three-dimensional network.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.All H atoms were located in a difference map and freely refined.The F atoms of the trifluoromethyl group are disordered over two sites in a 0.515 (6): 0.485 (6) ratio.The C-F bond lengths in the disordered trifluoromethyl group were constrained to be the same (using SADI), as were the thermal parameters of the F atoms (using EADP).(Rigaku OD, 2023), SHELXT (Sheldrick, 2015a), SHELXL2018 (Sheldrick, 2015b), ORTEP-3 for Windows (Farrugia, 2012) and PLATON (Spek, 2020).

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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å

Figure 1
Figure 1 Molecular structure of the title compound, showing the atom-labeling scheme and with displacement ellipsoids drawn at the 50% probability level.The intramolecular N-H� � �Br, C-H� � �F and C-H� � �N hydrogen bonds are shown as dashed lines.Only the major disorder component is shown for clarity.

Figure 3
Figure 3 Packing viewed along the b-axis with the C-O� � �� and C-Br� � �� interactions indicated by dashed lines.
Figure 4The three-dimensional Hirshfeld surface for the title compound, plotted over d norm .

Figure 5 A
Figure 5 A view of the two-dimensional fingerprint plots for the title compound, showing (a) all interactions, and delineated into (b) F� � �H/H� � �F, (c) O� � �H/H� � �O, (d) N� � �H/H� � �N, (e) F� � �O/O� � �F, and (f) F� � �N/N� � �F interactions.The d i and d e values are the closest internal and external distances (in A ˚) from given points on the Hirshfeld surface.

Table 2
Experimental details.
Computer programs: CrysAlis PRO