Crystal structure and Hirshfeld surface analysis of two 5,11-methanobenzo[g][1,2,4]triazolo[1,5-c][1,3,5]oxadiazocine derivatives

In the crystals of 9-bromo-2,5-dimethyl-11,12-dihydro-5H-5,11-methanobenzo[g][1,2,4]triazolo[1,5-c][1,3,5]oxadiazocine (I) and 7-methoxy-5-methyl-2-(pyridin-4-yl)-11,12-dihydro-5H-5,11-methanobenzo[g] [1,2,4]triazolo[1,5-c][1,3,5]oxadiazocine (II), N—H⋯N hydrogen bonds link the molecules to form inversion dimers in I and chains along the [010] direction in II.


Chemical context
In organic synthesis, a useful method to develop a chemical complexity from simple starting building blocks is the application of multicomponent reactions (MCRs) (Dö mling et al., 2012;Van der Heijden et al., 2013). When aminoazoles having at least two non-equivalent reaction centres are used as building blocks , the method is generally characterized by ambiguous selectivity and different reaction outcomes (Murlykina et al., 2018). According to Sedash et al., Biginellilike MCRs of 3-amino-1,2,4-triazole with aldehydes and -carbonyl CH-acids may generate several types of heterocyclic products (Sedash et al., 2012). The same starting compound with acetone and a 2-hydroxybenzaldehyde derivative under acidic conditions leads to the formation of different products (Gorobets et al., 2010;Kondratiuk et al., 2016;Gü mü ş et al., 2017;Komykhov et al., 2017).

Structural commentary
The molecular structures of compounds I and II are illustrated in Figs. 1 and 2, respectively. The conformations of the two compounds are very similar, as shown by the structural overlap of the two compounds [r.m.s. deviation = 0.005 Å (Mercury; Macrae et al., 2008)], illustrated in Fig. 3. In I, the triazole ring (N2-N4/C11/C12) is inclined to the benzene ring (C1-C6) by 85.12 (12) , compared to 76.96 (8) in II. In the central 6-oxa-2,4 2 -diazabicyclo[3.3.1]nonane moiety, ring (N1/N4/C7-C9/C11) has a half-chair conformation in both compounds, while ring O1/C5-C9 has an envelope conformation, with atom C8 as the flap, in both compounds. The mean planes of these two rings are almost normal to each other, with a dihedral angle of 86.94 (11) in I and 88.69 (8) in II. In compound II, the pyridine ring (N5/C13-C17) is almost coplanar with the triazole ring, having a dihedral angle of 4.19 (8) . The bond lengths and angles in the title compounds are very close to those observed for similar compounds, for example, the pyridin-3-yl analogue of compound II (Gü mü ş et al., 2018); see also section Database survey.

Supramolecular features
In the crystal of I, molecules are linked by a pair of N-HÁ Á ÁN hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif (Table 1 and Fig. 4). The dimers are linked by C-HÁ Á Á Table 1 Hydrogen-bond geometry (Å , ) for (I).

Figure 1
The molecular structure of compound I, with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The molecular structure of compound II, with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. and C-BrÁ Á Á interactions forming layers parallel to the bc plane (Table 1 and Fig. 4).
The conformations of all four compounds resemble those of compounds I and II, with the dihedral angle between the triazole and benzene rings varying from ca 71.20 to 87.37 , compared to 85.12 (12) and 76.96 (8) in compounds I and II, respectively.
The geometrical parameters of the four compounds are very similar to each other and to those of compounds I and II. The C9-O1 and C5-O1 bond lengths are 1.456 (3)  A view along the a axis of the crystal packing of compound II. Dashed lines denote intermolecular hydrogen bonds (Table 2).

Figure 4
A view along the a axis of the crystal packing of compound I. Dashed lines denote the intermolecular N-HÁ Á ÁN hydrogen bonds, forming an inversion dimer with an R 2 2 (8) ring motif (Table 1). C-HÁ Á Á and C-BrÁ Á Á interactions are shown as blue arrows (Table 1).

Hirshfeld surface analysis
The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional (2D) fingerprint plots (McKinnon et al., 2007) were performed with Crystal-Explorer17 (Turner et al., 2017). The Hirshfeld surfaces were generated using a standard (high) surface resolution with the three-dimensional (3D) d norm surfaces mapped over a fixed colour scale of À0.378 (red) to 1.282 Å (blue) for compound I and from À0.259 (red) to 1.216 Å (blue) for compound II. The red spots on the surface indicate the intermolecular contacts involved in the hydrogen bonds. In Fig. 6(a), the identified red spot is attributed to the HÁ Á ÁN close contacts. Also in Fig    the neighbouring molecules for compound I. Similarly, the red spots on the surface correspond to C-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds in compound II (Fig. 6b). Fig. 7(a) shows the 2D fingerprint plot of the sum of the contacts contributing to the Hirshfeld surface of compound I represented in normal mode. 2D fingerprint plots provide information about the major and minor percentage contribution of the interatomic contacts in compound I. The blue colour refers to the frequency of occurrence of the (d i , d e ) pair and the grey colour is the outline of the full fingerprint (Zaini et al., 2019). The fingerprint plots (Fig. 7b) show that the HÁ Á ÁH contacts clearly make the most significant contribution to the Hirshfeld surface (42.4%). In addition, CÁ Á ÁH/HÁ Á ÁC, NÁ Á ÁH/HÁ Á ÁN and BrÁ Á ÁH/HÁ Á ÁBr contacts contribute 17.9, 14.6 and 14.1%, respectively, to the Hirshfeld surface. Much weaker OÁ Á ÁH/HÁ Á ÁO (5.0%), BrÁ Á ÁN/NÁ Á ÁBr (2.7%), BrÁ Á ÁC/ CÁ Á ÁBr (1.8%) and BrÁ Á ÁBr (1.0%) contacts also occur. In particular, the OÁ Á ÁH/HÁ Á ÁO contacts indicate the presence of intermolecular C-HÁ Á ÁO interactions.
Similarly, for compound II, the HÁ Á ÁH interactions appear in the middle of the scattered points in the 2D fingerprint plots with a contribution to the overall Hirshfeld surface of 48.5% (Fig. 8b). The contribution from the NÁ Á ÁH/HÁ Á ÁN contacts, corresponding to the N-HÁ Á ÁN interactions, is represented by a pair of sharp spikes characteristic of a strong hydrogen-bond interaction (16.9%) (Fig. 8d). The whole fingerprint region and all other interactions are displayed in Fig. 8.
Views of the molecular electrostatic potential, in the range À0.0500 to 0.0500 a.u. using the STO-3G basis set at the Hartree-Fock level of theory, for compounds I and II are shown in Figs. 9(a) and 9(b), respectively. In Fig. 9(a), the N-HÁ Á ÁN hydrogen-bond donors and acceptors are shown as blue and red areas around the atoms related with positive (hydrogen-bond donors) and negative (hydrogen-bond acceptors) electrostatic potentials, respectively. Also, in Figs. 9(a) and 9(b), the N-HÁ Á ÁN and C-HÁ Á ÁO contacts in compounds I and II are given in the molecular electrostatic potential mapped surface showing the interaction between neighbouring molecules.

Synthesis and crystallization
The synthesis of the title compounds ( The view of the three-dimensional Hirshfeld surface of (a) compound I and (b) compound II, plotted over the electrostatic potential surface.

Figure 10
The synthesis of (a) compound I and (b) compound II.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. For compound I, the nitrogenbound H atom was located in a difference Fourier map and refined subject to a restraint of N-H = 0.86 (2) Å , while for compound II, the nitrogen-bound H atom was also located in a difference Fourier map and was freely refined. For both compounds, the C-bound H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.97 Å and U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) otherwise.     where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.70 e Å −3 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.

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Acta Cryst. (2019). E75, 492-498 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.