Umpolung of Organometallic Compounds by Electrochemical Reactions and Its Applications to Carbon-Carbon Bond Formation

我们发现，α-杂原子取代的有机锡化合物的阳极氧化会导致碳-锡键的断裂，并在碳上引入亲核试剂。在这一反应的基础上，我们发展了分子间和分子内碳-碳键的形成反应，为有机合成提供了有用的工具。例如，含有碳-碳双键的α-锡基醚和氨基甲酸酯的阳极氧化导致了有效的环化。在环化产物中的一个原始烯烃碳上引入了一个氟原子，这表明来自Bu_4NbF_4(支持电解质)的氟离子以亲核的形式攻击了环化阳离子。Bu_4NPF_6也是一种有效的氟源。本方法一般适用于内环合成六元环和七元环。内切环合成五元环不成功。本文概述的方法是电化学碳-碳键形成和含氟化合物合成的一种新方法，我们还发展了分子间碳-碳键的形成。α-杂原子取代的有机锡化合物在烯丙基硅烷或硅烯醇醚作为碳亲核试剂的存在下的阳极氧化也进展顺利，得到了相应的偶联产物。我们在本项目中开展的反应为有机金属化学和电化学有机化学提供了新的方面。

We have found that anodic oxidation of alpha-heteroatom-substituted organotin compounds results in the cleavage of the C-Sn bond and the introduction of a nucleophile onto the carbon. Therefore, the electrochemical oxidation provides an efficient method for"umpolung"of organotion compounds.On the basis of this reaction we have developed intermolecular and intramolecular carbon-carbon bond formation reactions which provide useful tools in organic synthesis.For example, the anodic oxidation of alpha-stannyl ethers and carbamates containing carbon-carbon double bonds lead to effective cyclization. A fluorine atom is introduced onto one of the original olefinic carbons in the cyclized product, indicationg that fluoride ion from Bu_4NBF_4 (supporting electrolyte) attacked the cyclized cation as nucleophile. Bu_4NPF_6 was also found to be effective as the fluoride source. The present method is generally applicable to endo cyclization to form six- and seven-membered rings. Endo cyclization to form a five-membered ring was not successful. The methord outlined here is a new approach to both electrochemical carbon-carbon bond formation and the synthesis of fluorine-containing compounds.We have also developed an intermolecular carbon-carbon bond formation. The anodic oxidation of alpha-heteroatom substituted organotin compounds in the presence of allylsilanes or silyl enol ethers as carbon nucleophiles also proceeds smoothly to give the corresponding coupling products.The reactions we have developed in this project provide new aspects of organometallic chemistry and electro-organic chemistry.