4,4′-Dichloro-3,3′,5,5′-tetramethyl-2,2′-[(3aR,7aR/3aS,7aS)-2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl)bis(methylene)]diphenol

In the title compound, C25H32Cl2N2O2, there are two intramolecular O—H⋯ N hydrogen-bonding interactions between the hydroxy groups on the aromatic rings and the two N atoms of the heterocyclic group. The cyclohexane ring adopts a chair conformation and the imidazolidine unit to which it is fused has a twisted envelope conformation. The asymmetric unit comprises one half-molecule which is completed by a twofold rotation axis. A C—H⋯O interaction is observed in the crystal structure.

In the title compound, C 25 H 32 Cl 2 N 2 O 2 , there are two intramolecular O-HÁ Á Á N hydrogen-bonding interactions between the hydroxy groups on the aromatic rings and the two N atoms of the heterocyclic group. The cyclohexane ring adopts a chair conformation and the imidazolidine unit to which it is fused has a twisted envelope conformation. The asymmetric unit comprises one half-molecule which is completed by a twofold rotation axis. A C-HÁ Á ÁO interaction is observed in the crystal structure.

Comment
The presence of p-halo substituent in the phenol ring afforded structural consequences such as the deformation of the ring observable in the bond distances and the bond angles values, which is related with the existence of resonance effect (X = Br, Cl) and inductive effect (X = F), according to theoretical results using the MP2 and density functional (B3LYP) methods (Zierkiewicz, et al. 2000 and. Theoretical investigations using NBO analysis suggested that p-chloro substituent induces a decrease of electron density in the lone pair orbital of the O atom with a reinforcement of the delocalization of electronic density to aromatic ring observable in a slight shortening of C-O and C-C bonds (Zierkiewicz, et al. 2004).
With the aim to understand the effect of electron-donating groups in the p-halophenol derivatives, we synthesized the title compound (I).
The molecular structure and atom-numbering scheme for (I) are shown in Fig. 1. Selected angles and bond lengths are listed in Table 1. These results show the existence of intramolecular hydrogen bonding interactions between the hydroxy H atom and the nitrogen atoms in the imidazolidine moiety. The shorter H-O distance (0.827 (17) Å) in comparison with the p-chlorophenol derivative (Rivera, et al. 2010), indicates a decreasing hydrogen-bonding strength. However, since the N···H and the N···O distances (table 1)  However, the observed C1-C2 and C4-C5 bond length are longer in comparison with the 3,5-dimethyl-4-chlorophenol (Cox, 1995) and the p-chlorophenol derivative (Rivera, et al. 2010), indicating a lower tendency to form a quinoid-type structure, reducing the delocalization of electronic density presumably due the electron-donating effect of the methyl groups in the 3 and 5 positions.
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.