Crystal structure and Hirshfeld surface analysis of 4-bromo-2-[3-methyl-5-(2,4,6-trimethylbenzyl)oxazolidin-2-yl]phenol

In the crystal, neighboring molecules are linked into layers parallel to the (200) plane via C—H⋯O hydrogen bonds and C—H⋯π interactions. van der Waals interactions between parallel molecular layers help to strengthen the packing.

The title compound, C 20 H 24 BrNO 2 , is chiral at the carbon atoms on either side of the oxygen atom of the oxazolidine ring and crystallizes as a racemate. The 1,3-oxazolidine ring adopts an envelope conformation with the N atom in an endo position. The mean plane of the oxazolidine ring makes dihedral angles of 77.74 (10) and 45.50 (11) , respectively, with the 4-bromophenol and 1,3,5trimethylbenzene rings. In the crystal, adjacent molecules are connected via C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions into layers parallel to the (200) plane. The packing is strengthened by van der Waals interactions between parallel molecular layers. A Hirshfeld surface analysis shows that HÁ Á ÁH (58.2%), CÁ Á ÁH/HÁ Á ÁC (18.9%), and BrÁ Á ÁH/HÁ Á ÁBr (11.5%) interactions are the most abundant in the crystal packing.
In the context of our recent studies, herein we report the structural analysis of a 1,3-oxazolidine, synthesized on the base of racemic 1,2-amino alcohol. Theoretically, in the solid state, this 1,3-oxazolidine can exist as eight optical isomers due to two CH and one N-chiral center. However, NMR analysis of the obtained product indicated the formation of a pair of diastereoisomers in a 1:1 ratio (Khalilov, 2021) and singlecrystal X-ray analysis of the racemic mixture confirmed the 2R,3S,5R-and 2S,3R,5S-configuration of these isomers (Fig. 1).

Supramolecular features and Hirshfeld surface analysis
In the crystal, adjacent molecules are connected via C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions into layers parallel to the (200) plane (Table 1 The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ).

Contact
Distance Symmetry operation

Synthesis and crystallization
The title compound was synthesized using our recently reported procedure (Khalilov, 2021), and colorless needle-like crystals were obtained upon recrystallization from an ethanol/ water solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All C-bound H atoms were placed at calculated positions and refined using a riding model, with C-H = 0.95 to 1.00 Å , and with U iso (H) = 1.2 or 1.5U eq (C).
The hydroxyl H atom was found in a difference-Fourier map and was refined freely.   (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020).  (Rigaku OD, 2021) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.