The crystal structures of three disordered 2-substituted benzimidazole esters

The crystal structures of three benzimidazole esters containing aryl or heterocyclic substituents at position 2 are reported, and all three exhibit disorder of mol­ecular entities. In ethyl 1-methyl-2-[4-(prop-2-yn­oxy)phen­yl]-1H-benzimidazole-5-carboxyl­ate, C20H18N2O3, (I), the prop-2-yn-1-oxyphenyl unit is disordered over two sets of atomic sites having effectively equal occupancies, 0.506 (5) and 0.494 (5). The propyl substituent in ethyl 1-propyl-2-(pyren-1-yl)-1H-benzimidazole-5-carboxyl­ate, C29H24N2O2, (II), is disordered over two sets of atomic sites having occupancies 0.601 (8) and 0.399 (8), and the ester unit in ethyl 1-methyl-2-(5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1H-benzimidazole-5-carboxyl­ate, C21H19ClN4O2 (III), is disordered over two sets of atomic sites having occupancies 0.645 (7) and 0.355 (7). In each of the C—H⋯π(arene) hydrogen bonds in (I), the donor and acceptor form parts of different disorder components, so that no continuous aggregation is possible. The mol­ecules of (II) are linked by a single C—H⋯O hydrogen bond into C(10) chains, which are linked into sheets by a π–π stacking inter­action, whereas those of (III) are just linked into C(13) chains, again by a single C—H⋯O hydrogen bond. Comparisons are made with the structures of some related compounds.