| Radical reactions have become the source of many practical methods for organic synthesis on account of their mild reaction conditions and good functional group compatibility while the photo/electrocatalytic free radical reaction is currently a relative green way to generate radicals.Photocatalysis involves the utilization of a photosensitizer to absorb light energy in order to reach its excited state,which then further interacts with organic substrates to convert visible light energy into chemical energy,thereby generating active intermediates.The organic electrochemical reaction mainly occurs at the interface between the electrode and the solution,which means electrons are transferred between the electrode and the organic molecules.The electrical energy and chemical energy are mutually converted during this process and prompts the compounds in the reaction system to gain or lose electrons,thereby generating active intermediates.The continuous development of photo/electrocatalysis in recent years has invigorated the field of free radical chemistry.This dissertation mainly summarizes the visible-light catalyzed construction of bromo-containing azaspirotrienedione and the electrocatalytic carbonylation of the benzylic C-H bond with the presence of iodine via free radical pathways.Chapter 1:Introduction.The first section mainly demonstrates the concept and advantages of free radical chemistry,as well as common methods of generating free radical intermediates.In the second section,we mainly reviewed different methods of constructing spiro compounds based on free radical intermediates（free radical cyclization under thermochemical or photochemical reaction,and other methods of spirocyclization）,which highlights the merits and importance of photocatalysis.The third section contains the concepts and mechanisms of organic photocatalytic reactions and summarizes three types of organic photocatalytic reactions according to the activation modes between the photosensitizer and the substrate.The fourth section introduces the history,reaction process,and main advantages of electrochemical organic synthesis,which outlines the classification of electrochemical organic synthesis,namely direct electrochemistry and indirect electrochemistry（according to whether the substrate directly gains or loses electrons from the electrode surface or not）.Then we introduce the basic principles of selecting the reaction mediator and the advantages of indirect electrochemical synthesis,and then mainly outline the indirect electrochemical oxidation reactions involving iodine in recent years.According to the difference of iodine intermediates,these reactions can be divided into two categories:（1）reactions that generate molecular iodine or iodine radical intermediates;（2）reactions that form X-I bond intermediates.The fifth section discusses the research background and far-reaching significance of this topic.Chapter 2:Visible-light mediated construction of bromo-containing azaspirotrienedione from N-phenylpropynamide.In this chapter,we first chose N-phenylpropynamide,diethyl 2,2-dibromomalonate as the model substrate,rose bengal as the photosensitizer,and acetonitrile as the reaction solvent.The reaction conditions,including the type of photocatalysts,solvent,light source,additives,gas atmosphere,and the loading of photosensitizer,solvent,were optimized at room temperature.After obtaining the optimal conditions,we investigated the compatibility of the substrates and obtained 21 anticipated products with moderate to good yields.Various substituted N-arylpropionamide are well tolerated,and the yield can reach up to 95%.Then,we carried out a series of mechanism exploration experiments,mainly including control experiments,ultraviolet-visible absorption measurement,free radical quenching experiments,fluorescence quenching experiments,18O labeling experiments,free radical trapping experiments,and cyclic voltammetry experiments.Based on the integrated analysis of the above experimental data,we proposed a more feasible reaction mechanism.In summary,this reaction provides a green,mild,and convenient alternative for the synthesis of bromo-containing azaspirotrienedione.Chapter 3:Electrochemical oxidative carbonylation of benzyl C-H bond.First,we selected 2-Phenylacetophenone as the reaction substrate,carbon rod as the anode,platinum sheet as the cathode,triethylenediamine（DABCO）as the additive,acetonitrile as the solvent,and the reaction conditions（the type and the amount of electrolyte,additive and solvent,current density,electrode type,reaction time）were screened under a current of 7 m A.With optimal conditions established,we explored a wide scope of substrates and obtained the target product with moderate to good yields.We put forward a possible reaction mechanism through a series of control experiments,free radical quenching experiments,18O labeling experiments,and cyclic voltammetry experiments.Besides,the reaction condition is green,mild,simple and fast to operate and boasts high atom economy,which provides a green alternative method for the carbonylation reaction of the benzylic C-H bond. |
