Study On New Method For C-F Bond Activation Of Bromine Fluoride Reagent

The activation and transformation of C-F bonds is an attractive subject in organic synthesis,which opens a new way for the construction and modification of new molecules.Up to date,the main strategies for C-F bond activation rely on the formation of B-F,Al-F,Si-F,or Ge–F through metal catalysts for further conversion.Although myriads of publications have been reported for metal-mediated or catalyzed C-F bond activation,the metal-free activation of C-F bonds has never been documented so far.Halo difluoro reagents are an important class of fluorinating reagents,which have been widely applied for difluoroalkylation and difluoromethylation reactions of various compounds.In addition to the single cleavage for the production of difluoroalkyl radical and double cleavage for the formation of difluorocarbene,the difluoro reagents could also undergo the quadruple cleavage of compounds to be harnessed as the C1 synthon.However,the triple cleavage of halogenated difluoro compounds have yet to be developed.With respect to the undeveloped reactivity of halogenated difluoro compounds,in this dissertation,we mainly study the application of halogenated difluoro compounds as C2 synthon via selective triple cleavage in organic synthesis.This dissertation mainly involves the following three aspects:One:The development history of polyfluorine chemistry is summarized.The theoretical and practical significance of C-F bond activation are expounded.In addition,the research progress on C-F bond activation of fluorine-containing compounds at home and abroad in recent years is reviewed.Two:S₈-catalyzed selective triple cracking of bromodifluoroacetamide.In this strategy,the readily available o-phenylenediamine,2-aminothiophenol and2-aminophenol were used as substrates for the streamline synthesis of the value2-amide-substituted benzimidazoles,benzoxazoles,and benzothiazoles under mild conditions.Mechanism studies have shown that C2 sources are generated in situ by selective cleavage of two inertC（sp³）-F bonds and C-Br bonds on three bromodifluoroacetamides,while retaining weak C-R bonds.The implement of this strategy will further enrich the role of halogenated difluoro compounds and enrich organic fluorochemistry as well as medicinal chemistry.Three:S₈ has played a key role in organic synthesis as a cheap,non-toxic and easy-to-handle chemical.This work will further explore the defluorination mechanism of S₈ catalyzing the breakage of the triple bond of bromofluoro compounds（including the stabilization of a C-F bond and a C-H bond）.The mechanism study proposes that the C-F bond undergoes a thiocarbon transition after activation of the C-F bond State,which is a new S₈-catalyzed C-F bond activation mechanism,which greatly complements fluorine chemistry and sulfur chemistry.