Organic Synthesis Catalyzed by Cobalt Complexes with Co-C Bond

维生素B12依赖的酶，以钴为催化中心，介导伴随着碳骨架重排的各种异构化反应。在该反应中，钴-烷基络合物是关键中间体。为了模拟维生素B12在相关酶的疏水活性部位中的催化功能，我们一直在处理疏水性维生素B12的衍生物，这些衍生物的酯基取代了天然维生素B12的外周酰胺部分。在电化学条件下，研究了疏水性维生素B12衍生物在N，N-二甲基甲酰胺中催化5，6，7和8元脂环酮与羧酸酯和溴甲基的扩环反应中的碳骨架重排。所有衬底的扩环反应主要在-2.0Vvs.SCE下进行。ESR研究表明，该反应是通过自由基中间体进行的。我们还尝试合成了一种新型的具有钴-烷基络合物的有机金属催化剂。具有钴-碳键的烷基化络合物通过光解得到烷基。如果使用双钴络合物，它会在光解后生成环状化合物作为双自由基偶联化合物。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，通过一锅法合成了一种具有相互相似的席夫碱单元的双核配体。

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).