Study On The Construction Of Sulfonyl Fluoride Compounds Under Reduction Conditions

Hexavalent sulfur fluorine compounds have high chemical stability,but can be activated under specific conditions to achieve efficient chemical bond conversion and linking.This special combination of stability and reactivity determines that these compounds have unique reaction activity.In 2014,Professor K.Barry Sharpless proposed a new generation of click chemical reaction concept-hexavalent sulfur fluorine exchange reaction（Su FEx）based on the special reaction activity of hexavalent sulfur fluorine compounds,which provides an effective and reliable new tool for creating modular intermolecular connection.Su FEx reaction has received great attention and extensive research in the fields of organic synthetic chemistry,material chemistry,pharmaceutical chemistry,chemical biology and so on.However,the current method for introducing SO₂F into organic molecules is still very limited,which seriously limits the further research and application of Su FEx click reaction.Therefore,it is of great theoretical significance and practical application value to explore a series of efficient methods to construct various sulfonyl fluorides.To this end,our group proposed a new strategy of"free radical sulfur dioxide insertion and fluorination"for the construction of various valuable sulfonyl fluorides.As a continuation of our research,we started from cheap and easily available aromatic amines,alkyl carboxylic acids and olefins to efficiently construct a variety of C-SO₂F bonds under reduction conditions on the basis of the new strategy.Preliminary investigation on the mechanism was also carried out.Details of the contents are as follows:（1）Arylsulfonyl fluoride synthesis from aromatic amines.Aromatic amines are cheap raw materials and substrates in both laboratory research and industry.We first transformed various aryl amines into corresponding aryldiazonium salts,then added potassium pyrosulfite as sulfur dioxide source and electrophilic fluorination reagent（NFSI）as fluorine source,and successfully synthesized a number of arylsulfonyl fluorides via free radical sulfur dioxide insertion fluorination strategy in one-pot and two-step reactions.This method realizes the direct introduction of sulfonyl fluoride groups into arenes from abundant arylamines under transition-metal-free catalysis conditions,and features its mild and practical conditions and good functional group tolerance.（2）Alkylsulfonyl fluoride synthesis from alkyl carboxylic acids.Based on free radical sulfur dioxide insertion and fluorination strategy,starting from alkyl carboxylic acids,we used the corresponding reducing active NHPI ester as the free radical precursor,zinc powder and Na₂S₂O₄ as reducing agent and sulfur dioxide source to quickly and efficiently convert various alkyl carboxylic acids（including primary,secondary and tertiary acids）into valuable alkylsulfonyl fluorides.The method features ready availability of raw materials,broad functional group compatibility and mild reaction conditions.Preliminary mechanism study shows that the reaction might involve the formation of alkyl radical intermediates.（3）Visible light induced palladium catalyzed aryldifluoromethylation and fluorosulfonylation of olefins.Under light induced palladium catalyzed conditions,trifluoromethyl arenes produce aryldifluoromethyl radicals,which react with inactive olefins to generate new alkyl radicals.Based on free radical sulfur dioxide insertion and fluorination strategy,the new alkyl radicals realize aryldifluoromethylation and fluorosulfonylation of inactive olefins.