Electrophilic addition of 1 -[o- (phenylsulfanyl)phenyI] -2-(p-methoxypheny1)ethyne with electrophiles such as perchloric acid, tetrafluoroboric acid, bromine, and benzenesulfenyl chloride gave 1 -phenyl-I -benzothiophenium salts exclusively. The substituent effect on the intramolecular cyclization with electrophiles has been examined. The aryl-substituted alkynes afforded predominantly the cyclized 1 -phenyl-I -benzothiophenium salts but methyl-substituted alkynes yielded a mixture of the cyclized salt and the 1,2-addition product. In addition to the intramolecular cyclization at the intermediate vinyl cation or bridged ion, it is proposed, on the basis of the product from the reaction of methyl-substituted alkyne, that the 71 complex partly participates in the i n t ra m ol ec u I a r cyc I izat i o n .

Reaction of u-(aryloxy) phenylalkynes with electrophiles such as perchloric acid, tetrafluoroboric acid, benzenesulfenyl chloride, and iodine monochloride yielded dibenz [b,f] oxepine derivatives. Cyclization to the dibenz[b,f]oxepines competed with 1,2-addition of the electrophiles. The effect of substituents on the alkyne is also discussed. Paper 2/01532C

Reactions of 1-arylbenzo[b]thiophenium salts with methoxide anion in methanol caused the fission of the S+-C(2) bond of the thiophenium ring to produce o-(phenylthio)phenyl-substituted methoxyethenes, allenes, or alkynes.

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Acid‐induced cyclization of the phenoxytolan (I) yields the dibenzoxepin (IV).