Selective C-F Bond Activation Of Fluorinated Aromatics

In the past few decades,the C-F bond activation of organofluorine compounds has gotten widely attention.Researchers hope that some problems could be solved by intense research of C-F bond activation in the field of materials and pharmaceuticals industry.For examples,in the field of materials industry,waste organofluorine compounds could be transformed into degradable organic compounds throght C-F bond activation;the synthesis of specialty aromatics with a fixed partical fluorination pattern is often subject to the use of fluorinated building blocks in the field of pharmaceuticals industry,the current researches show hydrodefluorination is regarded as a promising approach to access partially fluorinated compounds from readily available polyfluorinated compounds.Althought researchers have achieved a series of achievement in the field of C-F bond activation,some key points have not been achieved.(Before 2013)For instance,selective C-F bond activation of polyfluorinated compounds to syntheses important organic building blocks — fluoride aryl boride.Transforming waste organofluorine compounds into degradable organic compounds by developing economical and easy-operated method.This thesis mainly starts with above research goals,and focuses on the following aspects:When explored iridium-catalyzed synthesis of aryl borides by means of C-F bond activation of aryl fluorides,perchance we found that diaryl ethers could be obtained by designed reaction system.The method was suitable for the aryl fluorides which equipped with electron withdrawing groups in the ortho/para position,and has excellent compatibility with other carbon-halogen bond on the aromatic cycle.However,this method hardly affected the general aryl fluorides on account of low catalytic activity of iridium complexes.We carried the stratge of “borrowing hydrogen” in the field of C-F bond activation.Ethanol as the hydride source is deprived of hydrogen by rhodium to form rhodium-hydride compound which selectively catalyzed hydrodefluorination of polyfluorinated aromatics to synthesis of partially fluorinated aromatics.On this basis we found ortho-C-F bonds could be selective actived by changing the phosphine ligands,and gave mono-hydrodefluorination and/or di-hydrodefluorination products.Further study showed that rhodium-catalyzed C-F bond activation and C-B bond formation could be realized without participation of ethanol,which was the initial target we wanted to achieve.We intended to expand rhodium-catalyzed borondefluorination to general aryl fluorides(without directing group).However,we failed to realise this target.A transition-metal free and directing group assisted C-F bond activation and C-N bond formation was developed.One-pot method for synthesis of nitrogen-containing heterocycles substituted diarylamines was realized under the condition of only lithium hydride as base.Ortho-C-F bond could be selective activated when polyfluoroaromatics were chosen as substrates.This synthetic process is probably suitable for industrial preparation by its lowest cost and mild reaction conditions.Besides,this method is valuable not only in synthesis of fluorescent dye but also with reference value for handing fluoride-rich waste in industry.In extensional experiment,C-F bond in 8-position of quinolines was selective activated in the same reaction condition.The synthetic aminoquinolines are very important structural motifs in polyolefin catalyst families.We explored palladium-catalyzed the arylation of aryl-substituted difluoroethylenes with organic phosphonium via C-F bond activation.The methodology was a new pathway to contruct C-C bond through C-F bond activation.However,the chart only described the discovery process and preliminary possible mechanism due to incomplete work.More research about optimization of reaction conditions and scope of the substrates will be completed by incomer.