2,2′-[(3aRS,7aRS)-Perhydrobenzimidazole-1,3-diyl)bis(methylene)]diphenol

The molecular structure of the title compound, C21H26N2O2, shows two intramolecular O—H⋯N hydrogen-bonding interactions. In the crystal structure, molecular chains are formed along the c axis through weak C—H⋯O interactions. Neighbouring chains are weakly associated along the a axis via C—H⋯π interactions.

The molecular structure of the title compound, C 21 H 26 N 2 O 2 , shows two intramolecular O-HÁ Á ÁN hydrogen-bonding interactions. In the crystal structure, molecular chains are formed along the c axis through weak C-HÁ Á ÁO interactions. Neighbouring chains are weakly associated along the a axis via C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).
In continuation of our research program on the structure, properties, and reactivity of aminal cages (pre-formed Mannich reagents), we report here the synthesis and crystal structure of the title compound, (I).
The crystal packing (Fig 2) displays weak intermolecular C-H···O interactions ( Table 1) that link pairs of enantiomers alternately to form a racemic chain along the c axis. Chains are linked along the a direction by C-H···π interactions (Table 1).

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.96 Å) and refined as riding with U iso (H) = 1.2U eq (C). The positions of the hydroxyl-H atoms were refined with U iso (H) = 1.2U eq (O).

Special details
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.