Visible-Light Induced Cross Coupling Of Radicals And Diazo Compounds

Visible-light induced radical reactions have been explosively developed over the past decade.Extensive research demonstrate that radical species have been greatly enriched due to the unique mechanism and excellent functional group tolerance under photoexcitation.Meanwhile,mild conditions,environmental friendliness and so on,make it superior to traditional radical reactions.Diazo compounds,due to its unique reactivity,have attracted great attention over the years.A series of transformations of diazo compounds have been established under heat or ultraviolet light,but the relavent work using visible-light are still rare.This thesis concentrates on the researches about the radicals and diazo compounds via visible-light catalysis,and the conversion which is difficult to accomplish by traditional free radical process was realized.It mainly includes the following two parts:Part one:synthesis of oxalate esters via photocatalyzed coupling of radicals,molecular oxygen and diazo compounds.This reaction describes that ?-bromoketones transformed to ?-carbonyl alkyl radicals using Eosin Y as photocatalyst,green LED as light source,and subsequently was trapped by oxygen and diazo compounds to construct a variety of oxalate esters.This was the first report on synthesis of unsymmetrical oxalates through radical process,meanwhile benefited from mild conditions,simple operation,and broad substrate scopes.Part two:photo-induced cross coupling of radicals and diazo compounds:direct construction of indoles.This part describes that under the irradiation of visible light and catalysis by Ru(bpy)3Cl2·6H2O,tertiary amines were triggered to generate ?-amino alkyl radicals,which then cross couple with diazo compounds,with further ring-closure and aromatization to furnish indoles.However,the unavoidable N-dealkylation of tertiary amines will take place and lead to secondary amines,which makes the yield is unsatisfactory.