Research Of Electrochemical Oxidative Carbon-heteroatom Bond Formation Dehydrogenerative Cross-coupling

Organic synthetic chemistry which is closely related to people’s daily life is the material basis of modern society.It always needs to pre-functionalize substrates in traditional cross-coupling reactions,while the direct oxidative dehydrogenation coupling reaction between R~1-H/R~2-H is undoubtedly a very ideal reaction mode.The electrochemical organic synthesis has a long history which dates back to the 1830s.In recent years,the methodology of organic electrochemistry synthesis has developed rapidly.Electrochemical oxidation could activate substrate molecules or redox mediators on the electrode surface by adjusting the anodic oxidation potential without adding external oxidants,which is in line with the requirements of atomic economy and green chemistry.The carbon hetero-bonding reactions realized by electrochemical anodic oxidation in recent years are reviewed here from the perspectives of oxidative cross-coupling and organic electrochemistry synthesis.The research topic of this dissertation focus on the oxidation of heteroatom-hydrogen bond to form the hetero radical.The concrete research contents are as follows:(1)The electro-oxidative C-H/N-H cross-coupling reaction between phenols and phenothiazines is realized and this is the first time for phenothiazine being applied in electrochemical organic synthesis,avoiding problems of metal residues and the use of chemical oxidants in traditional transition-metal-catalyzed C-N bonding reactions.Various phenols and various phenothiazines are well compatible.The o-para diamine reaction of phenol can be realized by adjusting the proportion of substrates.The synthesis of triphenylamine can also be achieved in two ways:using diphenylamine substrates and hydrolyzing phenothiazine products,and the amplification reaction of10 g magnitude has also been successful.The difference of oxidation potential between the two substrates was analyzed by cyclic voltammetry experiment and verified by constant pressure reaction.It was suggested that the reaction might undergo the radical addition process of phenol by radical cation which is produced after the oxidation of phenothiazine at the anode.(2)The cross-coupling reaction of aryl C-H/P-H catalyzed by electrochemical Mn(II)was developed to synthesize triaryl phosphorus oxides.Compared with traditional metal-promoted or superoxide-triggered radical processes,this reaction avoids the use of chemical oxidants and has other advantages such as short reaction time,mild reaction conditions and high atom utilization rates.Moreover,it fills the blank of cross coupling between thiophen or furan type heteroaromatics and diphenylphosphine oxides to some extent.This method can also realize the bisphosphatization of thiophenfuran,and the products have been reported to be used for the construction of photoelectric active complexes.Kinetic isotope effect experiments and cyclic voltammetry experiments prove that there is a radical addition process of phosphorus radicals to electron-rich aromatic hydrocarbons in the reaction,besides Mn plays the role of oxidizing diphenyl phosphorus oxides and stabilizing the phosphorus radicals produced by oxidation.