Synthesis and reaction of 1-aryl-1-benzothiophenium salts

摘要

Reaction of [o-(arylthio)phenyl]ethenes with bromine of ICI undergoes intramolecular cyclization to give 1-ary-1-benzothiophenium salts.Electrophilic addition of [o-(phenylthio)phenyl]alkynes with electrophiles such as HclO_4,HBF_4,Br_2,and PhSCl also affords 1-phenyl-1-benzothiophenium salts.Copper-catalyzed reaction of 1-benzothiophenes with diphenyliodonium triflate gives 1-phenyl-1-benzothiophenium triflates directly.This method is especially effective for the synthesis of parent 1-phenyl-1-benzothiophenium salt.Reaction of 1-phenyl-1-benzothiophenium salts with halide ions leads to the formation of 1-benzothiophenes and (Z)-haloethenes,while the reaction with alkoxide ions provides only (Z)-alkoxyethenes.In the cases of 2-alkyl-subituted and 3-unsubstituted benzothiophenium salts.allenes and alkynes are formed,respectively.Cycloaddition of 1-phenyl-1-benzothiopheniumsalte with cyclopentadiene or 1,3-diphenylisobenzofuran proceeds efficiently in the cases of less substituted 1-phenyl-1-benzothiophenium salts.Phenyl migration is observed in the thermolysis of 1-phenyl-1-benzothiiophenium triflates,while the phenyl migration competes with the dephenylationinthe photolysis.The rections observed in this study are attributed to the loss of aromaticity of the thiophene ring.