Electrochemcial Reduction Of Diarylketones And Aryl Alkenes

Reduction reactions represent a fundamental class of chemical transformations in the chemical industry.Particularly,the reduction of ketones or olefins is a highly attractive and challenging task in organic chemistry,with broad applications in the production of fine chemicals,fragrances,pharmaceuticals,vitamins,and functional materials.Despite the wide range of carbonyl deoxygenation reduction methods available,the Clemmensen reduction method and the Wolf-Kessina-Huang Minglong reduction method remain the most classical ones.Regrettably,these methods are characterized by harsh reaction conditions and significant by-product formation,which translates to serious environmental pollution.Additionally,classical methods for the reduction of unsaturated C-C bonds typically rely on metallic catalysts(e.g.,palladium,rhodium,iridium)and potentially hazardous hydrogen gas.It is,therefore,crucial to develop green,economical,and safe reduction methods that respect the environment.This thesis presents a novel electrochemical reduction method for the deoxygenation reduction of diaryl ketones and the hydrogenation reduction of aryl olefins or aryl alkynes.Specifically,the method is described as follows:(1)Electrochemical deoxygenation reduction of diaryl ketonesThe electrochemical deoxygenation reduction of diaryl ketones was achieved using acetonitrile as the primary proton donor,without the need for external reducing agents and under non-metallic catalytic conditions.The reaction was conducted under constant flow electrolytic conditions in a mixture of acetonitrile and tetrahydrofuran with N,Ndiisopropylethylamine as the catalyst.This innovative method exhibited broad substrate scope and was capable of reducing diaryl ketone compounds with various substituents,including methyl,phenyl,fluoro,and anthraquinone with a dicarbonyl group.Remarkably,the reduction yields exceeded 80% for most substrates.Detailed mechanistic studies were conducted through deuterium labelling,radical capture,and intermediate validation experiments,revealing the reaction to be a radical reaction with a plausible mechanism.Notably,the study emphasized the crucial role of acetonitrile solvent in the electrochemical reaction,which acted as a solvent,proton donor,and reactant simultaneously.The success of the scale-up experiments further demonstrated the potential of this electrochemical method for industrial application.(2)Electrochemical hydrogenation reduction of aryl alkenes and aryl alkynesBased on the establishment of the novel electrochemical reduction method,this study expanded its application to the electrochemical reduction of aryl alkenes and aryl alkynes.Firstly,the optimal reaction conditions for the electrochemical reduction of aryl alkenes were obtained through extensive exploratory experiments.Based on this,the optimal reaction conditions for aryl alkynes could be obtained by adjusting the current and controlling the reaction time.Subsequently,various aryl alkenes with different substituents(methyl,dimethyl,tert-butyl,and phenyl)could be reduced to the corresponding products with a yield of 60-95%.Then,the reaction mechanism was studied through deuterium labeling experiments and radical capture experiments,and it was found that acetonitrile was the main proton donor and that the electrochemical reaction process was a radical process.Finally,the reduction of aryl alkenes could be scaled up to the gram level,indicating that this electrochemical method has broad industrial application prospects.Compared to traditional methods,the electrochemical reduction of diaryl ketones,aryl alkenes,and aryl alkynes does not require non-renewable metal catalysts or chemical reducing agents,making it more environmentally friendly and efficient.Additionally,the multifunctional nature of the solvent under electrochemical conditions has important research significance and practical value.