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Organic Synthesis Catalyzed by Cobalt Complexes with Co-C Bond

Co-C键钴配合物催化有机合成

基本信息

批准号：
07651034
负责人：
HISAEDA Yoshio
金额：
$ 1.34万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Vitamin B12-dependent enzymes, involving the cobalt species as a catalytic center, mediate various isomerization reactions accompained by carbon-skeleton rearrangements. In this reaction, cobalt-alkyl complex is a key intermediate. In order to simulate the catalytic functions of vitamin B12 as excerted in the hydrophobic active sites of enzymes concerned, we have been dealing with hydrophobic vitamin B12 derivatives which have ester groups in place of the peripheral amide moieties of the naturally occurring vitamin B12. In this work, the carbon-skeleton rearrangements which was applied to the ring-expansion reactions as mediated by hydrophobic vitamin B12 derivatives were investigated under electrochemical conditions.The electrolysis of alicyclic ketones (5,6,7, and 8-membered rings) with a carboxylic ester and a bromomethyl group was carried out in N,N-dimethylformamide in the presence of a catalytic amount of hydrophobic vitamin B12. The ring-expansion reaction largely proceeded at -2.0 V vs.SCE for all the substrates. ESR study showed that the reaction proceed through radical intermediates.We also tried to synthesize a new organometallic catalyst with a cobalt-alkyl complex. An alkylated complex having a cobalt-carbon bond gives an alkyl radical by photolysis. If a dicobalt complex is used, it will give a cyclic compound as a coupling compound of biradical after photolysis. This study focused on developing a new catalyst for prepareing a cyclic copmpound. A new dinucleating ligand, which has schiff base unit liked each other with an ethylene apacer, was synthesized by one-pot reaction of salicylaldehyse, ethylenediamine, and methylenebis (4,4'-salicylaldehyde).

维生素b12依赖酶，涉及钴作为催化中心，介导各种异构化反应伴随碳骨架重排。在这个反应中，钴-烷基配合物是一个关键的中间体。为了模拟有关酶疏水活性位点中维生素B12的催化功能，我们一直在研究用酯基代替天然维生素B12外周酰胺部分的疏水维生素B12衍生物。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在环扩张反应中的应用。在N，N-二甲基甲酰胺中，在疏水维生素B12的催化量下，用羧酸酯和溴甲基进行了脂环酮（5,6,7和8元环）的电解。在-2.0 V vs.SCE下，所有底物的扩环反应基本进行。ESR研究表明该反应是通过自由基中间体进行的。我们还尝试用钴-烷基配合物合成一种新的有机金属催化剂。具有钴碳键的烷基化配合物通过光解生成烷基自由基。若采用双钴配合物，则光解后得到双基偶联化合物环状化合物。本研究的重点是开发一种制备环状化合物的新型催化剂。以水杨醛、乙二胺和亚甲基双（4,4′-水杨醛）为原料，通过一锅反应合成了一种具有席夫碱基的新型二核配体。