Novel Organic Synthesis Catalyzed by Hydrophobic Vitamin B_<12> Derivatives under Electrochemical Conditions

依赖于维生素B的酶催化各种异构化反应，而伴随碳骨架重排的异构化反应由于其催化性质而特别引起人们的兴趣。我们一直在处理疏水性维生素B12的衍生物，以模拟维生素B12在相关酶的疏水活性中心发挥的各种催化功能。在本研究中，我们首次证明了在电化学条件下，疏水维生素B_12&gt；催化的碳骨架重排反应。然后，我们制备了一种用疏水维生素B_12&gt；修饰的聚合物涂层碳电极，并将其用于碳骨架重排反应。带…的基板通过在β-CARBOB原子上放置两个吸电子基团，一个羧酸酯和一个羧酸酯、乙酰基和氰基的组合很容易得到相应的重排产物，这些重排产物来自于取代基的单独迁移。吸电子基团的表观迁移能力大小顺序为：COSR&GT；COR&GT；CO_2R&GT；CN。以疏水维生素B&lt；12&gt；和沸石CT-200为可聚合单体，在玻碳电极上制备聚合物涂层电极，并将其应用于卤代烷烃的碳骨架重排反应。以碳骨架重排产物为主，以疏水性维生素B_(12)为基础的产率较高。较少

Vitamin B_<12>-dependent enzymes catalyze various isomerization reactions, and the ones accompanied with carbon-skeleton rearrangements are of particular interest in view of their catalytic nature. We have been dealing with hydrophobic vitamin B_<12> derivatives in order to simulate various catalytic functions of vitamin B_<12> as exerted in the hydrophobic active sites of enzymes concerned. In this study, we demonstrate for the first time the carbon-skeleton rearrangement reactions catalyzed by a hydrophobic vitamin B_<12> under electrochemical conditions. Then, we prepared a polymer-coated carbon electrode, as modified with a hydrophobic vitamin B_<12>, and used it for the carbon-skeleton rearrangement reactions.The controlled-potential electrolyses of alkyl halides with various electron-withdrawing groups as catalyzed by a hydrophobic vitamin B_<12> were carried out, and the electrochemical carbon-skeleton rearrangements proceeded via formation of anionic intermediates. Substrates w … More ith two electron- withdrawing groups placed on the beta-carbob atom, combinations of one carboxylic ester and one of carboxylic ester, acetyl, and cyano moieties, readily gave the corresponding rearrangement products which were derived from individual migration of the substituent groups. The apparent migratory aptitude of electron-withdrawing groups was found to decrease in the order: COSR > COR > CO_2R > CN. A hydrophobic vitamin B_<12> with the cyano moiety at an axial site of the nuclear cobalt further enhanced the electrochemical carbon-skeleton rearrangement.The polymer-coated electrode was prepared with a hydrophobic vitamin B_<12> and Araldite CT-200 as a polymerizable monomer on the glassy carbon electrode, and applied to the carbon-skeleton rearrangement reactions of alkyl halide, having electron-withdrawing groups under electrochemical conditions. The carbon-skeleton rearrangement products were obtained as major ones, and the yields based on the hydrophobic vitamin B_<12> were quite large. Less