Visible-light Catalyzed Direct C-H Functionalization Of (Heter) Arenes With Aryl Diazonium Salts As Arylating Reagent

Due to its atom-economy,great potential in practical synthetic application,metal-catalyzed C-H bond activation/cross-coupling reactions have become one of hot topics in the current frontier of organic chemistry.Such a direct C-H conversion is able to simplify organic synthesis route,maximize utility of each atom participating in the reaction,and therefore achieve ultimate goal of atom-economy.Meanwhile,as a clean and readily available source,visible-light is an ideal promoter for organic reactions.However,the identification of the suitable photocatalyst that enables highly selective construction of organic scaffold,particularly chemical transformation via C-H bond activation,remains a great challenge.This thesis aimed at the visible-light catalyzed direct C-H functinalization of(hetero)arenes with aryl azo salts as arylating reagent.The following is the result from these investigations:(1)The screenings of photosensitizers of metal complexes revealed that Ru(bpy)3(PF6)2 functioned as a high efficient photocatalyst for C-H arylation of(hetero)arenes with aryl azo salts as an arylating reagent.(2)The investigations of the effects of a variety of reaction parameters on the reaction outcomes led to the establishment of the optimized reaction conditions that allows the targeted C-H arylation of heteroarenes to proceed at room temperature under visible-light radiation.(3)The optimized reaction conditions were applicable to a broad range of pyridine derivatives,offered the corresponding products in high yields with good selectivity and exhibited good functional group tolerance.At the same time,the similar reaction conditions enabled a variety of substituted benzenes to undergo such a C-H arylation reaction.All the products(24 in total)have been fully characterized by 1H and 13C NMR spectra and element analysis.In terms of its mild reaction conditions,high selectivity and good functional group tolerance,this protocol is expected to find wide application for organic synthesis.(4)The mechanistic studies on the title reaction have been conducted,which demonstrated that the target reaction may involve radical process.On the basis of the mechanistic studies,a possible mechanism has been proposed in the thesis.