Crystal structure of the di-Mannich base 4,4′-di­chloro-3,3′,5,5′-tetra­methyl-2,2′-[imidazolidine-1,3-diylbis(methyl­ene)]diphenol

The title compound, C(21)H(26)Cl(2)N(2)O(2), was prepared in a solvent-free microwave-assisted synthesis, and crystallizes in the ortho­rhom­bic space group Pna2(1). The imidazolidine ring adopts an envelope conformation and its mean plane is almost perpendicular to the two pendant aromatic rings [dihedral angles = 84.61 (9) and 86.54 (9)°]. The mol­ecular structure shows the presence of two intra­molecular O—H⋯N hydrogen bonds between the phenolic hy­droxy groups and imidazolidine N atoms. The two 3-chloro-6-hy­droxy-2,4-di­methyl­benzyl groups are located in a cis orientation with respect to the imidazolidine fragment. As a result, the lone pairs of electrons on the N atoms are presumed to be disposed in a syn conformation. This is therefore the first example of an exception to the ‘rabbit-ears’ effect in such 2,2′-[imidazolidine-1,3-diylbis(methyl­ene)]diphenol derivatives.