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Electroorganic Synthesis Mediated by Metalloenzyme Models

金属酶模型介导的有机电合成

基本信息

批准号：
09450333
负责人：
HISAEDA Yoshio
金额：
$ 8.64万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

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.

在本工作中，我们在电化学条件下研究了疏水性维生素B12衍生物介导的碳骨架重排反应。对具有不同吸电子基团的卤代烷进行了控制电位电解，通过阴离子中间体的形成有效地进行了电化学碳骨架重排。这些反应也适用于扩环反应。在催化量的疏水维生素B12存在下，我们在β-碳原子上进行了具有两个酯基和一个苯基的卤代烷的电解。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。这是利用电解电势选择迁移基团的第一个成功例子。我们还制备了一种带疏水的维生素B12，以改变对映体选择性。对一个外消旋卤代烷基化合物进行了控制电位电解，该化合物具有苯基、甲氧基和羧酸酯基团。简单的疏水维生素B12倾向于更有利地结合S对映体。另一方面，捆绑的疏水维生素B12更有利于R-对映体的结合。这些结果表明，烷基化配合物的稳定性主要取决于还原产物的对映选择性。我们制备了Salen型配体的双钴配合物作为催化剂。在双钴络合物存在下，在-1.4V vs.SCE条件下电解溴化苄时，主要产物为联苯基。这一结果表明，双钴络合物将是一种优良的二聚反应催化剂。