Study Of Oxidative Or Reductive Radical Reactions

Redox neutral radical reactions usually feature good atomic economy and have attracted great attention in recent years.But such reactions require that the redox potential between reactants or reactants and catalysts must be matched,thus limiting the diversity of reactions.Addition of oxidizing agents or reducing agents can overcome the restriction of potential matching and enrich the types of free radical reactions.This thesis mainly focus on improving the poor reaction diversity and selectivity of oxygen and boron radicals.We have realized deoxygenation of alkoxyl radicals under reduction condition,hydrogen abstraction by boron radicals under oxidation condition,and oxidation of tertiary amines and aliphatic aldehydes by perovskite catalysts under aerobic conditons.The four parts of the main contents are as follows:1)The deoxygenation of alkoxy radicals to obtain alkyl radicals under photoredox catalysis was achieved by using the oxygen-philicity of trivalent phosphorus compounds for the first time.This method overcomed the side reactions such asβ-fragmentation and hydrogen abstraction which are easy to occur for the alkoxyl radicals.With alcohol derived N-alkoxylphthalimides as alkoxyl radical precursors,deoxygenated allylation or alkenylation products were obtained by this protocol.In addition,derivatives of two natural products geraniol and menthol can also be involved in the reaction.These reactions features mild condition and good functional group tolerance.It is worth noting that the reactions based onβ-fragmentation,1,5-HAT（hydrogen atom transfer）,and 1,2-HAT of alkoxy radicals would all change the structure of the alkyl structure of the alkoxyl radicals,while our deoxygenation protocol could successfully avoid this problem.This protocol is of high significance in the late-stage modification of alcohols,especially natural products and drugs.2)The first boron radical activation of inert C（sp³）-H bond was achived by using the hydrogen abstraction ability of pyridine-boron radical.In the presence of phenylacetylenyl sulfone as radical acceptor,the alkynylation of common alkenes was accomplished by using hydrogen-abstraction ability of pyridine-boron radical generated from the reaction of cyanopyridine and B₂nep₂,affording a series of aryl alkyl alkynes in good yields.The key to the success of the reaction was oxidizing H（L）BNep with 4-cyanopyridine-1-oxide,successively promoting the reaction balance to the right.The results of two competitive experiment in mixed solvent indicated that pyridine-boron radical is relatively rare electron-deficient boron radical.3)Theα-C（sp³）-H functionalization of tertiary amines was achieved using oxygen as green terminal oxidant and perovskite CsPbBr₃ as heterogeneous photosensitizer.The reaction was realized by oxidizing tertiary amines to iminiums,followed by nucleophilic attack with TMSCN,nitromethane,and phosphite nucleophiles.The reaction features mild condition and broad substrate scope.Furthermore,perovskite CsPbBr₃ is cheap and recycable,suggesting its promising application prospect in green oxidation reaction.4)The green,precise,and selective oxidation method is a great challenge in organic chemistry.We have developed an oxidation methodology and successfully realized selective oxidation of aliphatic aldehydes,using air as oxidant and perovskite CsPbBr₃ as photosensitizer.With this oxidation method,we realized the Passerini reaction of two molecular of aldehydes and one molecular of isonitrile,in which one molecular of the two aliphatic aldehydes was in situ oxidized to carboxylic acid.The reaction features mild condition,good yield,and good functional group tolerance.Notably,isonitrile containing tetrastyrene moiety also underwent on the reaction successfully to provide the corresponding product bearing AIE effect.