Photocatalytic Translocation/cyclization Of Alkynyl Aldehydes Initiated By Fluoroalkylation Of Alkynes

The C-H bond functionalization remains a formidable challenge in organic synthesis.As compared to transition-metal-catalyzed C-H bond functionalization,the hydrogen atom transfer（HAT）triggered remote C-H bond functionalization represents a significant advance since it obviate the utilization of pre-functionalized directing groups that are often difficult to remove,especially in complex molecules.Moreover,the radical reaction has excellent functional group compatibility for this strategy.As such,the remote C-H bond functionalization initiated by radical addition to alkenes has made great progresses in the past years,however,the versions triggered by radical addition to alkynes are still rarely reported.Hence,this dissertation focuses on the development of new remote C-H bond translocation-cyclization reaction initiated by radical addition to alkynes.Based on our previous works on remote functionalization of aldehydes.A alknye fluoroalkylation triggered remote intramolecular fluoroalkylation of aldehydes has been developed.By using 2-alkynyl benzaldehydes as the starting material,K3PO4 as the base,fluoroalkyl halides as the fluoroalkylation reagent,Ir（ppy）₃ as photocatalyst,2-fluoroalkylated indanones are synthesized under room temperature at irradiation of blue LEDs.The reaction features mild reaction conditions,convenient to handle,high yields,and excellent stereoselectivity.Various radicals such as fluoroalkyl,perfluoroalkyl,and sulfonyl radcials are well amenable to this reaction.Of note,single 2,3-trans disubstituted indanone isomers are obtained,which is very attractive for synthetic application.Mechanistic studies indicate that the reaction proceeds via an oxidation quenching photocatalytic cycle,consisting of a sequential SET,radical addition of alkynes,1,5-HAT,5-exo-trig and hydrgoen abstraction from the solvent.It consititutes a new advance on the remote C-H bond functionalization initiated by alkenyl radicals.