Study On Electrochemically Dehydrogenative Cross-Coupling Between Quinoxalin-2(1H)-ones And Alcohols

Heterocyclics containing nitrogen and carbon-oxygen bonds have important applications in the fields of medicine and chemical materials.Especially the functionalized quinoxaline-2-ones have good anti-bacterial and anti-cancer activity.Traditionally,carbon-oxygen coupling is achieved through transition metal catalysis.However,the use of expensive metal catalysts and a large number of additives has limited its application in pharmaceutical synthesis.Electrochemistry achieves reduction and oxidation directly through the gain and loss of electrons,and has a higher atomic economy.The purpose of this paper is to develop an efficient,green,and mild electrochemical method to accomplish the cross-dehydrogenation coupling reaction of quinoxalinones and alcohols.The author achieved the oxidative dehydrogenation coupling of quinoxalinones and alcohols under electrochemical conditions.By optimizing the electrolyte,electrode material,current strength,and solvent,the optimal reaction conditions for the synthesis of 3-alkoxyquinoxalinone were finally determined.Later,the substrate scale of this transformation was explored,twenty nine 3-alkoxyquinoxalinones were synthesized in 25-85% yields.The successful gram scale reaction proved the practicability of the methodology.Finally,the authors explored the mechanism of this reaction through a series of control experiments including switching experiments,free radical experiments,and cyclic voltammetry.Among them,the switch experiment confirmed that the current was indispensable in the reaction;the free radical experiment revealed that the reaction went through a free radical mechanism;the cyclic voltammetry proved that the reaction mechanism might involve one-electron oxidation of quinoxalinone and exclud the possibility of alkoxy radicals.In summary,a highly efficient electrochemically dehydrogenative C-H/O-H cross-coupling between quinoxalin-2(1H)-ones and alcohols was developed under mild conditions.Using different types of alcohols as solvent,various 3-alkoxylated quinoxalin-2(1H)-ones was synthesized in a simple undivided cell at room temperature.This novel electrochemical cross-dehydrogenative coupling approach features broad functional group tolerance,metal-and oxidant-free conditions,and moderate to good yields.At the same time,this method has definite theoretical significance and application value.