Synthesis And Application Of S-(Pentafluorophenyl) Dibenzothiophene Sulfonium Salt

Organic fluorides are widely used in the fields of medicine,pesticides and materials because of their special properties.Polyfluoroaryl compounds are an important part of organic fluorides,but their synthesis methods are relatively limited.The main reason for the limited synthesis of polyfluoroaryl compounds is the limited types of polyfluoroaryl sources.Therefore,in order to enrich the synthesis methods of polyfluoroaryl compounds,it is necessary to develop more new polyfluoroaryl sources.In this paper,a pentafluorophenyl sulfonium salt was synthesized and used as a pentafluorophenyl donor reagent for the pentafluorophenylation of terminal acetylene.The main contents are as follows:1.A synthetic route of pentafluorophenyl sulfonium salt was developed.This route starts from 2-aminobiphenyl and bromopentafluorobenzene respectively,through the synthesis of thiocyanate ester and triethoxy(perfluorophenyl)silane reagent reaction to synthesize thioether.S-(pentafluorophenyl)dibenzothiophene trifluoromethesulfonate sulfonate was prepared by cyclization of sulfoxide with triflicanhydride.In order to obtain a lot of raw materials for the future research and to prepare sulfonium salt effectively,the synthesis route was optimized.Whether a large amount of pentafluorophenyl thioether can be synthesized effectively is the key step to determine whether the whole preparation process is efficient.Therefore,we focused on the synthesis of pentafluorophenyl thioether.Finally,thiocyanate and triethoxy(pentafluorophenyl)silicon were used to synthesize thioether,and the conditions of this reaction were optimized.Thioether can be obtained with a yield of 75% at 10 mmol.Then,the thioether was oxidized to sulfoxide,and the pentafluorophenyl sulfonium salt was synthesized by ring closure of sulfoxide with dichloromethane as solvent under the mediation of trifluoromethesulfonic acid,the yield was 61%.The structure of the sulfonium salt was confirmed by nuclear magnetic resonance(NMR)and X-ray single crystal diffraction analysis(XRD).2.In order to study the reactivity of the pentafluorophenyl sulfonium salt,the pentafluorophenylation reaction of the sulfonium salt with terminal alkynes was investigated.Taking 4-methoxyphenylacetyene as template substrate,the optimum conditions for the reaction of sulfonium salt with terminal alkynes were obtained: The pentafluorophenylated product was obtained by reaction with 10 mol% tetra-(triphenylphosphine)palladium and 5mol% cuprous iodide as catalyst,1.0 equiv triethylamine as base and dichloromethane as solvent at 30 ℃ under argon atmosphere for 12 h.The yield was up to 88%.The results show that the reaction can be applied to most aryl-terminated alkynes.It is proved that S-(pentafluorophenyl)dibenzothiophene sulfonium salt can be used as pentafluorophenyl functional group transfer reagent.