Development of Bio-mimic Electrochemical Reaction by using Cobalt Complex and Its Application

本文以金属酶维生素B_模拟物钴肟为碳自由基生成剂，发展了一种不含锡的碳自由基生成方法<12>。在无隔膜电解槽系统中，用牺牲锌阳极电还原再生低价钴催化剂。研究了2-卤甲基环戊烷-1，3-二酮的1，2-酰基重排反应，得到相应的环己烷-1，4-二酮。该反应用于合成官能化联芳基化合物。在钴肟催化下，2-卤甲基环戊烷-1，3-二酮的单缩醛经电还原得到环己烷-1，4-二酮单缩醛，产率较高。2-芳基-2-（卤甲基）环戊烷-1，3-二酮在苯溶剂中的Bu_3SnH还原导致重排，得到相应的环己烷-1，4-二酮，而1，4-氢醌在延长加热时间下以中等产率进行。2.本文报道了在钴络合物-牺牲电极体系中O-烷基肟的自由基环化反应，得到功能化的β-氨基缩醛。由伯、仲和叔烷基溴生成的自由基添加到碳-氮双键上，没有任何困难，并且它们的反应性没有任何差异。该反应受空间位阻因素的影响较小。3.研究了溴代缩醛与苯甲醛的三元化合反应，通过电化学自由基生成方法得到了相应的环化产物。以[Co^<III>（N_4）Cl_2]ClO_4为钴配合物时，效果最好。

We developed a tin-free method for carbon radical generation by using cobaloxime, which was used as a mimic of metalloenzyme vitamine B_<12>. Regeneration of low valency cobalt catalyst was carried out by electroreduction with a sacrifical Zn anode in an undivided cell system. Development of a catalytic radical generation method is very meaningful in the synthesis of commonly useful compounds.1.We investigated the 1,2-acyl rearrangement of 2-(halomethyl)cyclopentane-1,3-diones, giving the corresponding cyclohexane-l,4- diones by the electrochemical radical generation method. This reaction was utilized for the synthesis of functionalized biaryls. The electroreduction of monoacetals of 2-(halomethyl)cyclopentane-1,3-diones in the presence of cobaloxime as a catalyst afforded the cyclohexane-1,4-dione monoacetals in good yields. The Bu_3SnH-reduction of 2-aryl-2-(halomethyl)cyclopentane- 1,3-diones under refluxing in benzene resulted in the rearrangement, affording the corresponding cyclohexane-1,4-diones, and 1,4- hydroquinones proceeded in moderate yields when heating was prolonged.2.We present here the radical cyclization reaction of O-alkyloximes by using cobalt complex-sacrificial electrode system, giving functionalized β-aminoacetals. The radicals generated from primary, secondary, and tertialy alkyl bromides added to the carbon- nitrogen double bonds without any difficulty and difference in their reactivity. This reaction seems to be slightly influenced by steric factor in the cyclization process.3.We investigated the three component combination reaction of bromoacetal with benzaldehyde, giving the corresponding cyclization product by the electrochemical radical generation method. The best result was obtained by using [Co^<III>(N_4)Cl_2]ClO_4 as a cobalt complex.