Biphenyl- and phenylnaphthalenyl-substituted 1H-imidazole-4,5-dicarbonitrile catalysts for the coupling reaction of nucleoside methyl phosphonamidites.

Crystal structures are reported for three substituted 1H-imidazole-4,5-dicarbonitrile compounds used as catalysts for the coupling reaction of nucleoside methyl phosphonamidites, namely 2-(3',5'-dimethylbiphenyl-2-yl)-1H-imidazole-4,5-dicarbonitrile, C19H14N4, (I), 2-(2',4',6'-trimethylbiphenyl-2-yl)-1H-imidazole-4,5-dicarbonitrile, C20H16N4, (II), and 2-[8-(3,5-dimethylphenyl)naphthalen-1-yl]-1H-imidazole-4,5-dicarbonitrile, C23H16N4, (III). The asymmetric unit of (I) contains two independent molecules with similar conformations. There is steric repulsion between the imidazole group and the terminal phenyl group in all three compounds, resulting in the nonplanarity of the molecules. The naphthalene group of (III) shows significant deviation from planarity. The C-N bond lengths in the imidazole rings range from 1.325 (2) to 1.377 (2) Å. The molecules are connected into zigzag chains by intermolecular N-H···N(imidazole) [for (I)] or N-H····N(cyano) [for (II) and (III)] hydrogen bonds.