Study On The C-N Bond Formation Of C3-Position Of Quinoxaline-2(1H)-One Enabled By Visible Light Catalysis

Quinoxalinone and its derivatives,an important class of nitrogen-containing heterocyclic compounds,are widely present in natural products.They are important synthetic intermediates for pharmaceutical active molecules and functional materials.Among them,a part of C3-substituted quinoxalin-2(1H)-ones have biological activities such as anticancer,antibacterial,and antitumor.In recent years,the direct functionalization reactions of quinoxaline-2(1H)-one C3 has been developed in the field of organic synthesis.However,most of the synthetic methods are complex reactions that require the participation of transition metal catalysts,stoichiometric oxidants,bases or inorganic salts.Therefore,there are still great challenges in developing synthetic methods with simple operation,milder conditions,and green environmental protection.Studies in recent years have shown that the use of visible light to promote the transformation of organic reactions has become a common research method.In this study,quinoxalin-2(1H)-one and 1H-benzotriazole and their derivatives are the main research objects,and two new methods for the construction of C-N bonds have been developed using a mild and green visible light catalysis strategy:1、A visible light-catalyzed amination method for denitrogenation of quinoxalin-2(1H)-one C3 with benzotriazoles was developed.Through the optimization of the reaction photocatalyst,solvent,light source,reaction time,substrate ratio and reaction concentration,the optimal reaction conditions are obtained as follows: at room temperature,Rose bengal(5 mol%),solvent N,N-dimethylformamide,nitrogen atmosphere,35 W green LEDs irradiation for 54 hours.Under the optimal reaction conditions,different reaction substrates were expanded,and thirty kinds of 3-(arylamino)quinoxalin-2(1H)-one derivatives substituted with different functional groups were synthesized,and the reaction yield was 21-82%.The method is simple to operate which does not require transition metal catalysts,and it is suitable for a wide range of substrates,providing a new strategy for the C3 amination of quinoxalin-2(1H)-ones.2、A new visible-light-catalyzed reaction for the cross-dehydrocoupling of quinoxaline-2(1H)-one C3-position with 1H-benzotriazoles and other azoles at N1-position has been developed.Through the optimization of the reaction photocatalyst,solvent,light source,reaction atmosphere,substrate ratio and reaction time,the optimal reaction conditions were: at room temperature,Eosin B(5 mol%),acetonitrile as solvent,in oxygen atmosphere,35 W green LEDs illuminated for 48 hours.Under the optimal reaction conditions,quinoxalin-2(1H)-ones substituted with different functional groups,benzotriazoles and other azoles were expanded,and a series of target products were efficiently synthesized.The method is mild,which does not require transition metal catalysts or environmentally hazardous strong oxidants.It has a wide range of substrate applicability with yields of up to 99%,providing a new route for the C3-position coupling reaction of quinoxalin-2(1H)-ones.