Ethyl 1-tert-butyl-2-(4-hydroxy-3-methoxyphenyl)-1H-benzimidazole-5-carboxylate

In the title compound, C21H24N2O4, the benzimidazole ring system is almost planar, with a maximum deviation of 0.047 (1) Å and makes a dihedral angle of 88.44 (5)° with the attached benzene ring. In the crystal, molecules form infinite chains along the b axis by way of intermolecular O—H⋯N and C—H⋯O interactions. Weak C—H⋯π also contribute to the stabilization of the crystal structure.

In the title compound, C 21 H 24 N 2 O 4 , the benzimidazole ring system is almost planar, with a maximum deviation of 0.047 (1) Å and makes a dihedral angle of 88.44 (5) with the attached benzene ring. In the crystal, molecules form infinite chains along the b axis by way of intermolecular O-HÁ Á ÁN and C-HÁ Á ÁO interactions. Weak C-HÁ Á Á also contribute to the stabilization of the crystal structure.

Experimental
The title compound was synthesised according to the previous procedure described by us (Arumugam, Abd Hamid et al.  2010)). The product was recrystallised from EtOAc to afford the title compound as colourless crystals.

Refinement
The H atom attached to O1 was located in a difference map and refined isotropically. The remaining H atoms were positioned geometrically [CH = 0.93, 0.96 or 0.97 Å] and were refined using a riding model, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and 1.2 for all other H atoms. A rotating group model was used for the methyl groups.  Ethyl 1-tert-butyl-2-(4-hydroxy-3-methoxyphenyl)-1H-benzimidazole-5-carboxylate  (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.