Visible-light/electro-catalyzed Radical Addition And Cyclization Cascade Of Unsaturated Carbon-carbon Bonds

The notion that radical intermediates are chaotic,uncontrollable,and mysteriously baffling had been accepted for long,due to radical's unique single-electron structures and active chemical properties.In recent decades,many radical reactions have been reported,and the properties of radicals have been known gradually.There is growing evidence that radicals can react in a unique way,and some reactions can't even be done by traditional methods.It has great synthetic potential that the radicals obtained by visible-light-redox catalysis and electrocatalysis are added to the unsaturated carbon-carbon bonds,and then are followed by cyclization reaction.The thiocyanate can be used as a precursor for the synthesis of many sulfur-containing organic compounds,and plays an important role in the field of organic synthesis.The thiocyanate radical generated from thiocyanate by visible light catalysis can add to unsaturated compounds to obtain organic thiocyanate.This article described the visible-light-catalyzed radical addition and cyclization/spirocyclization cascade of ammonium thiocyanate with olefins/alkynes,and electrocatalytic radical addition and cyclization cascade of sodium trifluoromethylsulfinate with olefins.In the second chapter of this thesis,we described the radical addition and cyclization cascade reaction of methacryloylbenzamide with ammonium thiocyanate catalyzed by organic photocatalyst acridine perchlorate.First,we chose N-methacryloyl-Nmethylbenzamide and ammonium thiocyanate as substrates for the model reaction,and several conditions were investigated to obtain the optimum reaction conditions.Then,the substrate scope was expanded under the optimized conditions.25 thiocyanato-containing isoquinolinediones were prepared with yields of up to 89%,and all of the products were reported for the first time.According to the results of the control experiments,radical trapping experiments,fluorescence quenching experiments and cyclic voltammetry,a plausible mechanism was proposed.The reaction constructed C-S and C-C bonds in one pot,and molecular oxygen was the sole sacrificial reagent.The third chapter of this thesis reported the radical addition and spirocyclization cascade reaction of N-aryl propynamide with ammonium thiocyanate catalyzed by organic photocatalyst acridine perchlorate.We screened a series of conditions for the reaction of N-methyl-N,3-diphenylpropynamide and ammonium thiocyanate for the optimal coditions.Under the optimal conditions,the substrate scope was studied.22 spirocyclohexenylenedione derivatives,18 of which were reported for the first time,were prepared in moderate to good yields with a maximum yield of up to 95%.This protocol was also capable of constructing tricyclic product.The mechanism of the reaction was explored by control experiments,including radical trap experiments,fluorescence quenching experiments,and cyclic voltammetry.Electron transfer is one of the most important processes in organic chemistry,and many organic reactions are driven by electron transfer.Highly reactive radical cations or radical anions generated by the addition or removal of an electron from substrates are important intermediates in organic chemical reactions.Organic electrosynthesis is an ideal method to achieve the intermediates under mild conditions.Electricity can partially or even completely prevent the use of metal catalysts,stoichiometric oxidants or reducing agents.It is not only environmentally friendly,but also can simplify the synthetic steps.Indirect electrolysis uses catalytic amount of mediator to avoid direct electron transfer from the electrode to the substrates,and increases the rate,selectivity and yield of the reactions in most cases.In the fourth chapter of this thesis,we tried the reaction of using TEMPO as a mediator to generate a trifluoromethyl radical.N-methacryloyl-N-methylbenzamide and sodium trifluoromethylsulfinate were used as substrates for model reaction.The reaction conditions were optimized under constant current conditions to give the trifluoromethylated isoquinoline product in 73% yield.