Electroorganic Synthesis Mediated by Metalloenzyme Models

在这项工作中，疏水性维生素B12衍生物介导的碳骨架重排在电化学条件下进行了研究。对含不同吸电子基团的卤代烷进行了控制电位电解，通过形成阴离子中间体有效地进行了电化学碳骨架重排。这些反应也可以应用于扩环反应。我们在催化量的疏水维生素B_（12）存在下，对β-碳原子上有两个酯基和一个苯基的卤代烷进行了电解。在形成自由基中间体的条件下观察到苯基的迁移。在形成阴离子中间体的条件下检测到酯迁移产物。这是第一个利用电解电位选择迁移基团的成功例子。我们还制备了一种束缚的疏水维生素B12，以改变对映体选择性。对在同一碳原子上具有苯基、甲氧基和羧酸酯基的外消旋卤代烷进行了控制电位电解。简单的疏水性维生素B12倾向于更有利地结合S-对映体。另一方面，束缚的疏水性维生素B12更有利地结合R-对映体。这些结果表明，烷基化配合物的稳定性决定了还原产物的对映选择性。当在双钴络合物存在下于-1.4Vvs.SCE下电解苄基溴时，主要产物为联苄基。该结果表明，双钴配合物将是二聚反应的优良催化剂。

In this work, the carbon-skeleton rearrangements as mediated by hydrophobic vitamin B12 derivatives were investigated under electrochemical conditions. The controlled-potential electrolyses of alkyl halides with various electron-withdrawing groups were carried out, and the electrochemical carbon-skeleton rearrangements proceeded effectively via formation of anionic intermediates. These reactions can be also applied to the ring-expansion reactions. We have carried out the electrolysis of an alkyl halide having two ester groups and one phenyl group on the β-carbon atom in the presence of a catalytic amount of the hydrophobic vitamin B12. The migration of the pheny group was observed under the conditions forming an radical intermediate. The ester-migrated product was detected under the conditions forming anionic intermediate. This is the first successful example in selecting a migrating group by electrolysis potential. We have also prepared a strapped hydrophobic vitamin B12 in order to change the enantioselectivity. The controlled-potential electrolysis of a racemic alkyl halide having phenyl, methoxy, and carboxylic ester groups on the same carbon atom were carried out. The simple hydrophobic vitamin B12 tends to bind S-enantiomers more favorably. On the other hand, strapped hydrophobic vitamin B12 acts to bind R-enantiomers more favorably. These results suggested that the stability of alkylated complexes was dominated the enantioselectivity of reduction products.We prepared bis-cobalt complex with salen-type ligand for the catalyst. When electrolysis of benzyl bromide was carried out at - 1.4 V vs. SCE in the presence of the bis-cobalt complex, major product was bibenzyl. This result suggests that the bis-cobalt complex will be an excellent catalyst for dimerization reactions.