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

我们开发了一种以钴胺肟为模拟物的无锡碳自由基生成方法，钴胺肟是金属酶维生素B_<12>的模拟物。采用牺牲锌阳极电还原法在不分裂电池系统中对低价钴催化剂进行了再生。发展一种催化自由基生成方法对合成常用化合物具有重要意义。用电化学自由基生成法研究了2-（卤甲基）环戊烷-1,3-二酮的1,2-酰基重排，得到相应的环己烷- 1,4 -二酮。利用该反应合成了功能化双芳基。以钴胺为催化剂，电还原2-（卤甲基）环戊烷-1,3-二酮单缩醛，得到了收率较高的环己烷-1,4-二酮单缩醛。2-芳基-2-（卤甲基）环戊烷- 1,3-二酮在苯中回流的bu_3snh还原导致重排，产生相应的环己烷-1,4-二酮和1,4-对苯二酚，当加热时间延长时产率中等。本文采用钴配合物-牺牲电极体系，研究了邻烷基肟的自由基环化反应，得到了功能化β-氨基缩醛。由伯、仲、叔烷基溴生成的自由基加到碳氮双键上没有任何困难，其反应活性也没有任何差异。这个反应似乎受环化过程中的位阻因素的影响不大。研究了溴缩醛与苯甲醛的三组分组合反应，通过电化学自由基生成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，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.