Stereochemical Control in Electron-transfer Induced Reactions. Cyclic Voltammetry and Cathodic Reduction of Epimeric 3-Halogeno-6-nitro-5-cholestenes
作者:Takeo Sato、Takahiro Wada、Yoshihisa Komeichi、Masatsune Kainosho
DOI:10.1246/bcsj.58.1452
日期:1985.5
3β-halogeno derivatives were much shorter. On cathodic reduction 3β-derivatives gave a cyclosteroid, 6β-nitro-3α,5α-cyclo-5α-cholestane in a two-electron process, whereas 3α-derivatives gave a dimer, 6β,6′β-dinitro-3α,3′α-cholesta-4,4′-diene, as the major product via a one-electron process. Detailed CV studies were carried out for 6-nitro-5-cholestene as a model. The stereochemistry of 3,3′-dimer was established
对差向异构 3-halogeno-6-nitro-5-cholestenes 进行阴极电解和循环伏安测量。发现阴离子自由基的稳定性和命运高度依赖于同烯丙基卤素基团的立体化学。发现来自 3α-氯代和 3α-溴代衍生物的阴离子自由基的半衰期分别为 12.5 和 1.6 秒,而 3β-卤代衍生物的半衰期要短得多。在阴极还原时,3β-衍生物在双电子过程中得到环甾体 6β-硝基-3α,5α-环-5α-胆甾烷,而 3α-衍生物得到二聚体 6β,6'β-二硝基-3α,3' α-cholesta-4,4'-diene,作为单电子过程的主要产物。对 6-nitro-5-cholestene 作为模型进行了详细的 CV 研究。3,3'-二聚体的立体化学通过 1H NMR 测量确定。