Photocatalyzed Acidic C(sp~3)-H Bond Activation And Hydrocarboxymethylation Of Unactivated Alkenes

Compared with traditional free radical reactions,photocatalysis has been applied to many practical chemical reactions for its characteristics of green,safety,mild conditions,excellent chemical selectivity and wide applicability of substrates,and has brought dawn to the renaissance of free radical chemistry.Because most organic compounds cannot absorb visible light,a catalytic amount of visible light catalyst is needed to convert the light energy into chemical energy,and then the substrates are activated by single electron transfer or energy transfer pathway to generate highly reactive free radicals,radical ions and triplet intermediates to participate in the organic reactions.In view of the unique catalytic properties of photocatalysis,we hope to take advantage of this platform to develop new activation methods for cheap and bulk chemicals,so that they can be used to synthesize high-value compounds under mild conditions to achieve efficient and low-cost synthesis of important chemicals.The thesis contains with following three parts:Part ?:Brief introduction of photoredox catalysis and the addition reaction of olefins with?-carbonyl radical.This chapter firstly introduced the great advantages of visible light as clean energy in organic synthesis,and then outlined the principle and development process of photocatalysis.Finally,we introduced the addition reactions of?-carbonyl radicals generated by photocatalysis and olefins in terms of bifunctionalization,cycloaddition,and reductive coupling in recent years.Part ?:Photocatalyzed metal-free alkylheteroarylation of unactivated olefins via direct acidic C(sp~3)-H bond activationThis chapter firstly introduced the research progresses of C-H bond activation in photoredox catalysis,and summarized the radical activation reactions of acidic sp~3 C-H bonds.Then,based on previous research,we utilized the acyloxy radical generated by photoredox catalysis from diacylperoxide to achieve radical activation of acidic sp~3 C-H bonds at room temperature,and a series of 1,7-dicarbonyl compounds containing a heteroaryl ring were synthesized in one step by heteroaryl migration strategy.This activation method based on hydrogen atom transfer was not only suitable for the activation of chain ketones and esters,but also for cyclic ketones and lactone compounds.In addition,common solvents such as acetonitrile,dichloromethane,1,2-dichloroethane and chloroform could also give good results.This simple and mild approach had a wide range of substrates and maked a good complement to photocatalyzed C-H bond activations.Part ?:Photocatalyzed hydrocarboxymethylation of unactivated alkenesThis chapter firstly introduced the traditional synthesis method of two-carbon added fatty acids from olefins,in which the malonate play a key role.This multi-step strategy has shortcomings of harsh conditions and low atomic economy.In order to overcome this disadvantage,we had developed a photocatalyzed approach for the hydrocarboxymethylation of unactivated alkenes.Among them,bromoacetic acid was used as a two-carbon(C2)synthon for the first time for photocatalytic direct synthesis of carboxylic acids.This efficient synthetic method was not only easy to operate,but also suitable for a wide range of olefin substrates,furthermore,this method could enable the direct late-stage functionalization of natural product derivatives.In addition,we could easily complete the synthesis of marketing drugs such as Tirofiban and Cinacalcet from carboxylic acids synthesized by this strategy,which further embodying the important value of this method.