Deschamps N M, Kaldis J H, Lock P E, Britten J F, McGlinchey M J
Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1.
J Org Chem. 2001 Dec 14;66(25):8585-91. doi: 10.1021/jo0108820.
Treatment of 1-[axial]-(trimethylsilylethynyl)cyclohexan-1-ol with dicobalt octacarbonyl results in a conformational ring flip such that the bulky dicobalt-alkyne cluster moiety now occupies the favored equatorial site. However, when a 4-tert-butyl substituent is present, the coordinated alkynyl group retains its original axial or equatorial position. Complexation of trans-[diaxial]-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol brings about a chair-to-chair conformational inversion such that both cluster fragments now occupy equatorial sites. In contrast, cis-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol reacts with Co(2)(CO)(8) to yield the twist-boat conformer in which the two axial hydroxy substituents exhibit intra-molecular hydrogen bonding. Likewise, the corresponding reaction of cis-1,4-bis(trimethylsilylethynyl)cyclohexane-1,4-diol with Co(2)(CO)(8) leads to a twist-boat, but in this case, the molecules are linked through inter-molecular hydrogen bonds. Eight of these cobalt clusters have been characterized by X-ray crystallography, and the potential use of twist-boats in synthesis is discussed.
用八羰基二钴处理1-[轴向]-(三甲基甲硅烷基乙炔基)环己醇会导致构象环翻转，使得庞大的二钴-炔簇部分现在占据有利的赤道位置。然而，当存在4-叔丁基取代基时，配位的炔基保持其原来的轴向或赤道位置。反式-[双轴向]-1,4-双(三苯基甲硅烷基乙炔基)环己烷-1,4-二醇的络合导致椅式到椅式的构象反转，使得两个簇片段现在都占据赤道位置。相比之下，顺式-1,4-双(三苯基甲硅烷基乙炔基)环己烷-1,4-二醇与Co₂(CO)₈反应生成扭船式构象异构体，其中两个轴向羟基取代基呈现分子内氢键。同样，顺式-1,4-双(三甲基甲硅烷基乙炔基)环己烷-1,4-二醇与Co₂(CO)₈的相应反应也生成扭船式构象异构体，但在这种情况下，分子通过分子间氢键相连。其中八个钴簇已通过X射线晶体学表征，并讨论了扭船式构象异构体在合成中的潜在用途。
