6,6′-Dimethyl-2,2′-[1,3-diazinane-1,3-diylbis(methylene)]diphenol

In the molecule of the title compound, C20H26N2O2, the 1,3-diazinane ring adopts a slightly distorted chair conformation and the hydroxybenzyl substituents occupy equatorial positions on the N atoms of the heterocyclic ring. There are two intramolecular O—H⋯N hydrogen bonds between the N atoms of the 1,3-diazinane ring and the hydroxy groups of the aromatic rings, with an S(6) set-graph motif. However, the two observed intramolecular hydrogen-bond distances were different. Considering that both N atoms experience the same chemical environment, it is surprising to see the difference in O⋯N distances [2.6771 (14) and 2.8123 (12) Å]. The crystal structure is further stabilized by a C—H⋯π interaction.

In the molecule of the title compound, C 20 H 26 N 2 O 2 , the 1,3diazinane ring adopts a slightly distorted chair conformation and the hydroxybenzyl substituents occupy equatorial positions on the N atoms of the heterocyclic ring. There are two intramolecular O-HÁ Á ÁN hydrogen bonds between the N atoms of the 1,3-diazinane ring and the hydroxy groups of the aromatic rings, with an S(6) set-graph motif. However, the two observed intramolecular hydrogen-bond distances were different. Considering that both N atoms experience the same chemical environment, it is surprising to see the difference in OÁ Á ÁN distances [2.6771 (14) and 2.8123 (12) Å ]. The crystal structure is further stabilized by a C-HÁ Á Á interaction.
Cg2 is the centroid of the C6-C11 aromatic ring.  The hydroxybenzyl substituents occupy equatorial positions. However, the dihedral angles between the mean planes of the benzene rings and the mean plane of the heterocyclic ring were 77.80 (15)° and 80.03 (10)°. This observation indicates there was different spatial positioning, which is more evident with the dihedral angle between both phenyl rings.
The angle between the two aromatic rings is 58.431 (38)°.

Refinement
All hydrogen atoms were discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice H atoms bonded C atoms were kept in ideal positions with C-H distance 0.96 Å during the refinement. The methyl H atoms were allowed to rotate freely about the adjacent C-C bonds. The hydroxyl H atoms were found in difference Fourier maps and their coordinates were refined freely. All H atoms were refined with thermal displacement coefficients U iso (H) set to 1.5Ueq(C, O) for methyl and hydroxyl groups and to to 1.2Ueq(C) for the CHand CH 2 -groups.

Special details
Experimental. CrysAlis PRO (Agilent Technologies, 2010) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement. The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.