Application Of C-H Bond Activation In The Construction Of Difluorinated And Heterocyclic Compounds

C-H bond activation has emerged as a simple and efficient method to construct C-C and C-X bonds due to the abundance of C-H bonds and the high atom economy.Compared with the reactions need for transition-metal catalysts,stoichiometric amounts of oxidants and harsh reaction conditions,it is of great research significance to develop C-H bond activations featuring in mild conditions,without transition-metal catalyst,oxygen as the terminal oxidant or with high regioselectivity.When the C-H bond activation strategy is applied to the construction of compounds with potential biological activity,this kind of reaction has an important applicational value.Therefore,this dissertation studies the activation reactions of different C-H bonds by different methods,and applies them to the construction of difluorinated and heterocyclic compounds.The main contents are shown as below:A visible-light induced direct C（sp³）-H difluoroalkylation of xanthenes with difluoroenolsilanes was developed through HAT-ORPC pathway.Various substituted xanthenes,acridines,thioxanthene,1,3-diphenylpropenes and 1,3-diphenylpropargyl are found to be efficient substrates to construct a series ofα,α-difluoroketones.Theα,α-difluoroketones can also be further converted to other fluorine-containing compounds.This reaction uses cheap and easily available non-transition metal Na₂-eosin Y as photocatalyst and air as the oxidant,providing an atom economic method for the difluoroalkylation of C（sp³）electrophiles.A series of vinyl-substituted 3,4-dihydroisoquinolones were constructed by a palladium-catalyzed C（sp²）-H allyl/cyclization reaction between N-sulfoylbenzoamide and allyl alcohols.Compared with the allyl substrate with active leaving group（LG）,the allyl alcohol substrate used in this reaction is easy to obtain and produces only water as a byproduct,which is very environmentally friendly.However,due to the low leaving group tendency of hydroxyl group,there is a competition reaction betweenβ-OH elimination andβ-H elimination,and the tandem reaction involving C（sp²）-H allylation has not been developed.The oxidation process with oxygen as the terminal oxidant was also realized in this reaction.