Stable carbenes. Synthesis and properties of benzimidazol-2-ylidenes
作者:N. I. Korotkikh、G. F. Raenko、T. M. Pekhtereva、O. P. Shvaika、A. H. Cowley、J. N. Jones
DOI:10.1134/s1070428006120116
日期:2006.12
A new stable crystalline carbene, 1,3-bis(1-adamantyl)benzin-ddazol-2-ylidene, was synthesized by decomposition of 1,3-bis(I-adamantyl)-2,3-dihydro-1H-benzimidazol-2-ylacetonitrile on heating under reduced pressure. Heteroaromatic 1,3-R-2-disubstituted benzimidazol-2-ylidenes, both stable (R = 1-Ad) and generated in situ (R = Me, Bzl), as well as 1,3,4,5-tetraphenyliniidazol-2-ylidene (generated in situ), reacted with acetonitrile to give the corresponding insertion products, 1, 3 -disubstituted 2-cyanomethyl-2,3-dihidro-1H-(benz)imidazoles. The geometric parameters of 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, determined by X-ray analysis, suggest its lower aromaticity as compared to imidazol-2-ylidenes and 1,2,4-triazol-5-ylidenes. The structures of 2-cyanomethyl-2,3-dihydro-1H-benzimidazoles, 2-cyanomethyl-1,3,4,5-tetraphenyl-2,3-dihydro-1H-imidazole, and 1-(1-adamantyl)-5-cyanomethyl-3,4-diphenyl-4,5-dihydro-1H-1,2,4-triazole are characterized by partial conjugation in the heteroring; some compounds exhibit luminescence under UV irradiation. 1,3-Bis(1-adamantyl)benzimidazol-2-ylidene reacted with molecular sulfur in benzene to give 1,3-bis(1-adamantyl)-2,3-dihydro-1H-benzimidazole-2-thione, but it failed to react with selenium under analogous conditions.