Crystal structures of (12E)-12-(4-benzylidene)-7,7,16-trimethyl-3-(4-methylphenyl)-1-oxa-16-azatetracyclo[11.2.1.02,11.04,9]hexadeca-2(11),4(9)-dien-5-one and (12E)-12-(4-bromobenzylidene)-73-(4-bromophenyl)-,7,16-trimethyl-10-oxa-16-azatetracyclo[11.2.1.02,11.04,9]hexadeca-2(11),4(9)-dien-5-one

The title compounds, C32H35NO2, (I), and C30H29Br2NO2, (II), differ by the presence of a bromine atom instead of a methyl atom in the para position of two phenyl rings of compound (II), with an r.m.s. deviation of 0.27 Å between these compounds.


Chemical context
The tropane skeleton is found widely in both natural and manufactured medications. It is the fundamental component of many beneficial alkaloids, including atropine, scopolamine, and cocaine, whose derivatives are important in the treatment of neurological and psychiatric conditions such depression and panic disorder (Cheenpracha et al., 2013;Afewerki et al., 2019;Dongbang et al., 2021). It is also a key component in the synthesis of newer types of drugs. Tropane derivatives are used to treat irritable bowel syndrome, peptic ulcers, colic, cystitis, and pancreatitis thanks to their anti-spasmodic properties. In view of the above importance, we have undertaken a singlecrystal X-ray diffraction study for the title compounds, and the results are presented herein.

Structural commentary
The molecular structure of the title compounds (I) and (II) are illustrated in Figs. 1 and 2, respectively. Fig. 3 shows the superposition of the two compounds except for atom C21 using Qmol (Gans & Shalloway, 2001); the r.m.s. deviation is 0.27 Å . The methylphenyl rings in (I) are oriented at a dihedral angle of 57.7 (1) . The methyl atoms C31 and C32 in (I) deviate by À0.036 (1) and 0.053 (1) Å , respectively, from the rings to which they are attached. The bromophenyl rings in (II) are oriented at a dihedral angle of 54.3 (1) . Bromine atoms Br1 and Br2 deviate by 0.050 (1) and 0.037 (1) Å , respectively, from the rings to which they are attached.

Supramolecular features
In the crystal of (I), molecules associate via C-HÁ Á ÁO intermolecular interactions (C14-H14Á Á ÁO2 i , Table 1 A view of the molecular structure of compound (II), showing the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. Table 1 Hydrogen-bond geometry (Å , ) for (I).

Figure 1
A view of the molecular structure of compound (I), showing the atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Hirshfeld surface analysis
To further characterize the intermolecular interactions in the title compound, we carried out a Hirshfeld surface (HS) analysis (Spackman & Jayatilaka, 2009) using Crystal Explorer 21 (Spackman et al., 2021) and generated the associated two dimensional fingerprint plots (McKinnon et al., 2007). The HS mapped over d norm in the range À0.0701 to +1.6693 a.u. for compound (I) and À0.1162 to +1.5964 a.u. for compound (II) are illustrated in Figs. 6 and 7, using colours to indicate contacts that are shorter (red areas), equal to (white areas), or longer than (blue areas) the sum of the van der Waals radii (Ashfaq et al., 2021).
The two-dimensional fingerprint plots provide quantitative information about the non-covalent interactions and the crystal packing in terms of the percentage contribution of the interatomic contacts (Spackman & McKinnon, 2002;Ashfaq et al., 2021). The HS analysis reveals that HÁ Á ÁH (74.2%) and The centrosymmetrical dimer formed in compound (II) via C-HÁ Á ÁO hydrogen bonds (dashed lines). The dimers are linked by C-HÁ Á Á interactions (dashed lines). For clarity H atoms, not involved in these interactions have been omitted.

Figure 6
A view of the Hirshfeld surface mapped over d norm in the range À0.0701 to +1.6693 arbitrary units for compound (I).

Figure 7
A view of the Hirshfeld surface mapped over d norm in the range À0.1162 to +1.5964 arbitrary units for compound (II).

Figure 4
The crystal packing of the title compound (I) viewed along b axis. The C-HÁ Á ÁO and C-HÁ Á Á intermolecular interactions are shown as dashed lines. For clarity, H atoms not involved in these interactions have been omitted.

Synthesis and crystallization
Compound (I) was synthesized from a mixture of 8-methyl-8azabicyclo[3.2.1]octan-3-one and two equivalents of 4-methylbenzaldehyde and 5,5-dimethylcyclohexane-1,3dione dissolved in ethanol/acetic acid and refluxed for 12 h. After completion of the reaction, as indicated by thin layer chromatography (TLC), the mixture was cooled to room temperature, poured into ice-cold water and neutralized with a saturated solution of sodium bicarbonate. The compound was further recrystallized from ethanol to obtain crystals suitable for single crystal X-ray analysis.
Compound (II) was synthesized from a mixture of 8-methyl-8-azabicyclo[3.2.1]octan-3-one, two equivalents of 4-bromobenzaldehyde and 5,5-dimethylcyclohexane-1,3-dione dissolved in ethanol/acetic acid and refluxed for 12 h. After completion of the reaction, as indicated by thin layer chromatography (TLC), the mixture was cooled to room    temperature, poured into ice-cold water and neutralized with a saturated solution of sodium bicarbonate. The compound was further recrystallized from ethanol to obtain crystals suitable for single crystal X-ray analysis.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. In both (I) and (II), H atoms were placed in idealized positions and allowed to ride on their parent atoms: C-H = 0.93-0.98 Å , with U iso (H) = 1.5U eq (Cmethyl) and 1.2U eq (C) for other H atoms.