Studies On The Transition-metal-free Radical Coupling Reaction Of Azaallyl Anions As Super Electron Donors

Radical coupling reaction is an effective strategy to construct C-C bonds.This kind of reaction is favored by organic synthetic chemists due to its mild reaction conditions.The traditional approaches to forming radicals require addition of transition metals and organic metal catalysts,which leads to challenges of sustainability.Therefore,it is extremely necessary to develop a transition-metal-free method of forming radicals.Organic super electron donors(SEDs)are a category of highly active organic reductive reagents.They can reduce aryl or alkyl halides by single electron transfer(SET)process,to form corresponding aryl or alkyl radicals which undergo a radical-radical coupling reaction to construct new C-C bonds.This process does not require addition of transition metals,which usually makes the reaction simpler,lower-cost and more efficient.Azaallyl anions have been proved to be SEDs in reactions.They can reduce aryl or alkyl iodides to form corresponding aryl or alkyl radicals.At the same time,they are oxidized to azaallyl radicals,whichcan take part in radical-radical coupling reaction as coupling reagents.In this dissertation,radicals were generated by azaallyl anions acting as SEDs to realize a series of transition-metal-free radical-radical coupling reactions.These reactions included the synthesis of benzofurylethylamine derivatives through a unique cascade radical cyclization/intermolecular coupling for the first time,the synthesis of homoallylamine derivatives by a novel radical-radical coupling reaction,and the direct C-H functionalization of aliphatic oxa-heterocycles by a novel C-H activated radicalradical coupling reaction.This dissertation is divided into five chapters.In the first chapter,the research progress on three new methods of radical formation and azallyl anions as SEDs in radical reactions in recent years were reviewed.In the second chapter,a transition-metal-free cascade radical cyclization/intermolecular coupling reaction was developed for the first time,which was applied to the synthesis of benzofurylethylamine derivatives.In this reaction,azaallyl anions serve as SEDs and coupling reagents to form corresponding radicals with 2-iodophenyl propadienyl ether through a SET process.Then,they underwent a cascade radical cyclization/intermolecular coupling reaction to realize the synthesis of benzofurylethylamine derivatives.This expedient approach has wider universality.It enables the synthesis of a range of multifunctional polycyclic(heterocycle)benzofurans that would otherwise be difficult to prepare.It also enables the synthesis of a series of benzo six-or seven-oxo-heterocyclic derivatives.It is noteworthy that this method does not require addition of transition metals and ligands,avoiding challenges of sustainability,expense,and separation of trace transition metal-containing impurities.In the third chapter,a novel transition-metal-free radical-radical coupling reaction was developed,which was applied to the synthesis of homoallylamine derivatives.In this reaction,azaallyl anions serve as SEDs and coupling reagents to form corresponding azaallyl radicals and allyl radicals with allyl phenyl ethers through a SET process.Then,they underwent a regioselective radical-radical coupling reaction to construct new C(sp3)-C(sp3)bonds,and to realize the synthesis of homoallylamine derivatives.In the fourth chapter,a novel transition-metal-free C-H activated radical-radical coupling reaction was developed,which was applied to the construction of C(sp3)C(sp3)and direct C-H functionalization of aliphatic oxa-heterocycles.In this method,azaallyl anions underwent a SET process with additive agent aryl iodides to form corresponding azaallyl radicals and aryl radicals.Aryl radicals further underwent a hydrogen atom transfer(HAT)process with aliphatic oxa-heterocycles to form corresponding aliphatic oxa-heterocyclic radicals.Then,they underwent a novel radical-radical coupling reaction with azaallyl radicals to construct new C(sp3)-C(sp3)bonds and achieve direct C-H functionalization of aliphatic oxa-heterocycles.In the last chapter,the research work of the dissertation was summarized,and the future investigation direction was suggested.