Studies On Several Arylations With Arylsulfonium Salts

With the rapid development of organosulfur chemistry,tetravalent organosulfur compounds have been widely used in the fields of materials,pharmaceutical,and synthetic chemistry for their special physical and chemical property.In particular,arylsulfonium salts have been drawing extensive attention from scientists in recent years.Although arylsulfonium salts have been already used as electrophilic arylation reagents or aryl radical precursors in a series of chemical transformations,the arylation with arylsulfonium salts has not been fully explored.Therefore,the development of new arylation reactions based on the stable and highly active arylsulfonium salts is significant for constantly advancing the sulfonium chemistry.This thesis focuses on the selective C_aryl-S bond activation and application of arylsulfonium salts in new chemical reactions,which has accomplished several types of arylation with these salts through reasonable design and optimization,the detail as follow:1.The first selective N-arylation of arylamines using alkylarylsulfonium salts was achieved under Pd/Cu-cocatalysis.Owing to the good alkylation ability of alkylarylsulfonium salts,the competitive N-alkylation reaction needs to be inhibited by regulating the selectivity of C-S bond activation.In this part,the choice of alkylarylsulfonium salts bearing lengthened alkyl chains and the use of copper catalyst could suppress the N-alkylation side reaction.The palladium catalyst realized the selective cleavage of C_aryl-S bond and sustained the reaction catalytic cycle.Thanks to the effect of steric hindrance,butyl（aryl）（mesityl）sulfonium salts provided ideal C_aryl-S bond selectivity in the reaction that enabled synthesis of various diarylamines in good yields.2.By utilizing the fact that the 2-position C-H bonds of azoles are easily activated by the copper catalyst,the Pd/Cu-catalyzed C-H arylation of azoles with arylsulfonium salts was developed,which synthesized twenty-three 2-arylazoles including the natural products Balsoxin and Texamine.Additionally,sixteen2-arylazoles were constructed using arenes as the starting materials by combining the highly regioselective C-H sulfenylation and Pd/Cu-catalyzed C-H arylation.The“one-pot”and gram-scale syntheses of the representative products were also demonstrated.Besides,the gout drug Febuxostat was prepared in good yield through this formal C-H/C-H cross-coupling starting from 2-fluorobenzonitrile.3.Combination of C-H sulfenylation and light-induced trifluoromethylselenolation enabled the indirect C-H trifluoromethylselenolation of thirty arenes including drugs,which provided basic materials for screening potentially bioactive aryl trifluoromethyl selenides.In this photoredox trifluoromethylselenolation of arylsulfonium salts with[Me₄N][Se CF₃],the possible key intermediates were tentatively suggested according to the UV-vis and ¹⁹F/⁷⁷Se NMR measurements.A plausible reaction mechanism involving radical and ligand-coupling pathways was proposed on the basis of the light on-off experiment,the quantum yield,and the free radical trapping experiments.