Study On Dicarbofunctionalization Of Olefins By Photocatalysis

With the revival of the field of visible light catalysis in 2008,various synthetic problems have been given answers that belong to photocatalysis.Photocatalysts catalyze the activation of small molecules with mild conditions.It has become a parallel to enzyme catalysis and metal catalysis in organic synthesis.Especially with the emergence of organic photocatalysts and the realization of some photochemical reactions that did not require external photocatalysts,which resulting the application range of free radical reactions has been greatly expanded.Photochemical strategies are simple and low-cost,which conforms to the definition of green chemistry.As for a kind of olefins widely exist on nature products,the research on various functionalizations of olefins has always been a hot topic.With the rise of photocatalysis,more and more people utilize the photocatalysis to develop new strategies and methods in organic synthesis.By using the characteristics of free radical reactions,a series of free radical reactions have been developed after reasonable substrate designed and condition controlled,which achieve highly functionalized molecules via radical tandem reactions.However,under the current development situation with the increasing application of free radical reactions,free radical chemistry is also facing some new challenges and opportunities:1)How to better explain the reaction process of free radicals with olefins?2)How to understand the bonding nature of the coupling of free radicals with olefins?3)How to reveal the general law of the reaction of free radicals with olefins?With the help of the advantages and characteristics of theoretical chemistry,this thesis starts from the step-by-step coupling model,analyzes the known free radical reaction characteristics,utilizes the electrophilic and nucleophilic characteristics of aryl radicals,and combines the molecular orbitals of olefins to design a new radical reaction model.In the second chapter of this thesis,a new type of photocatalysis for aryl alkylation of olefins was developed.In this method,aryl halides and electron deficient alkenes were selected as the aryl source and alkyl source respectively.The Csp2-Csp3 dicarbonization of oxa-alkenes was realized under simple and mild metal free conditions.Moreover,the substrates of alkyl halides,oxa-alkenes and electron deficient alkenes were investigated.The results show that the corresponding products can be obtained for fluorine,chlorine,bromine,iodine and other aryl halides.It can also be compatible with various terminal olefin and internal olefin substrates for vinyl ether substrates.For electron deficient alkenes,the corresponding products can be obtained regardless of whether the carbon carbon double bond is connected with sulfone,cyanogen,ester,ketone and other functional groups.In the third chapter of this thesis,we developed a 1,3-addition reaction of aryl radical to electron deficient alkenes.The reaction starts from phenyl iodide and phenyl bromide,and produces aryl radical under the action of photocatalyst.Then,1-aryl-3-one,1-aryl-3-sulfonyl and other products are synthesized by radical addition reaction of electron deficient olefins.The range of aryl halides was expanded,and the reaction result of aryl iodide was better than the aryl bromide.Moreover,it has good reactivity for halogenated heterocycles such as pyridine and benzothiophene.For electron deficient alkenes,e.g α-β Unsaturated ketone or acrylonitrile can also be reacted.