Development of Efficient Reactions and Synthesis of New Types of Chiral Complexes by Appling 'Cis-Effect' of Hard Lewis Bases

配体的空间和电子性质对金属配合物的反应性有很大影响。虽然已经提出了许多配体效应，但“顺式效应”被认为对反应性的影响很小。我们重点研究了“硬”路易斯碱的“顺式效应”，并利用这种效应实现了钴配合物催化的高效有机转化和新型钴配合物的对映选择性合成。八羰基二钴介导的[2+2+1]炔烃、烯烃和一氧化碳共环生成环戊烯酮的反应被称为Pauson-Khand反应，已被用于构建包括天然产物在内的五元环。虽然已经开发了许多催化体系，但催化活性通常较低至中等。为了提高催化活性，我们开始研究一种基于“硬”路易斯碱的“顺式效应”的新型催化剂。合成了多种具有“硬”路易斯基团的二芳基乙基六羰基二钴配合物，并对其在Pauson-Khand反应中的催化活性进行了研究。其中，[η^2, μ^2-1-（2-氨基苯基）-2-苯乙基]六羰基二钴具有最高的催化活性，是该反应周转率的世界纪录。复合物内胺的“顺式效应”显著提高了反应性。与（η^2，μ^2-炔）六羰基二钴具有相似结构的苄基三钴非羰基，在炔烃和/或烯烃的反应中是惰性的。一旦氢化物与钴配位，氢化物的“顺式效应”改变了钴的电子性质，因此，团簇在1-庚-6-炔的环化反应中表现出更高的催化活性。由于（η^2，μ^2-二乙基乙烯）六羰基二钴配合物与取代的二苯乙烯具有相似的结构，某些配合物可能具有轴向手性。然而，自从发现手性络合物以来，一直没有关于它的报道。结果表明，在催化量为(2R,3R)-2,3- o -环己基-1,1,4,4-四苯基苏糖醇的条件下，络合反应生成手性[η^2，μ^2-1-（2,5-二甲基苯基）-2-苯乙基]六羰基二钴。少

Steric and electronic nature of ligand greatly influences to reactivity of the metal complexes. While a number of ligand-effects have been proposed, the ‘cis-effect', is considered as small influence to the reactivity. We focused on the ‘cis-effect' of ‘hard' Lewis bases and utilized this effect to realize efficient organic transformations catalyzed by cobalt complexes and enantioselective synthesis of novel cobalt complexes.The dicobalt octacarbonyl-mediated [2+2+1]-cocyclization of an alkyne, an alkene, and a carbon monoxide to produce cyclopentenones is known as the Pauson-Khand reaction and has been utilized for construction of five-membered rings including natural products. While a number of catalytic systems have been developed, the catalytic activity was usually low to moderate. To improve the catalytic activity, we started to investigate a new catalyst based on the use of ‘cis-effect' of ‘hard' Lewis bases. Various diarylethynehexacarbonyldicobalt complexes with ‘hard' Lewis ba … More se substituents at the orttho position of one of aryl groups were synthesized and surveyed their catalytic activity in the Pauson-Khand reaction. Among them, [η^2, μ^2-1-(2-aminophenyl)-2-phenylethyne]hexacarbonyldicobalt showed the highest catalytic activity, which was the world record in the turnover number of the reaction. The 'cis-effect' of the amine inside of the complex dramatically increased the reactivity.Benzylidynetricobalt nonacarbonyl, which had similar structure with (η^2,μ^2-alkyne)hexacarbonyldicobalt, was known to be inert in reaction of alkynes and/or alkenes. Once hydride coordinated to the cobalt, the ‘cis-effect' of the hydride changed the electronic nature of the cobalt, and therefore, the cluster turned to show higher catalytic activity in cyclization of 1-hepten-6-ynes.Since (η^2,μ^2-diarylethyne)hexacarbonyldicobalt complexes has similar structure with substituted stilbenes, some of the complex might have axial chirality. However, there has been no report about the chiral complex since it was discovered. We found that chiral [η^2,μ^2-1-(2,5-dimethylphenyl)-2-phenylethyne]hexacarbonyldicobalt was produced when the complexation was carried out in the presence of a catalytic amount of (2R,3R)-2,3-O-cyclohexylidene-1,1,4,4-tetraphenylthreitol. Less