Oxidation of aromatic compounds: XVI. Radical cations derived from acetylenic compounds with electron-withdrawing groups: Reactions and ESR parameters

One-electron oxidation of aryl-substituted acetylenes ArC equivalent to CX where X is an electron-withdrawing group gives different products, depending on the X substituent. Acetylenic substrates with medium-strength electron-withdrawing substituents, X = CO2R, COAr, COR, PO(OEt)(2), give rise to tetrasubstituted ethenes X(ArCO)C=C(COAr)X. Compounds with strong electron-withdrawing groups (X = COCF3, COCO2R, CN) are converted into furan derivatives. Probable mechanisms of transformations of ArC equivalent to CX radical cations into the final products are discussed. Radical cations derived from disubstituted acetylenes were characterized by ESR spectroscopy.