Skeletal transformations of perfluoro-1-ethyl-1-phenylbenzocyclobutene in the reaction with antimony pentafluoride

Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

“…Expansion of the four-membered ring in I to five-membered can also follow path b involving opening of the four-membered ring in cation D. Cyclization of benzyl type cation E thus formed yields phenylindanyl cation F, and hydrolysis of the latter leads to compound XX. Analogous mechanism was proposed by us previously for skeletal transformations of perfluorinated alkyl-, dialkyl-, and alkylphenylcyclobutabenzenes in SbF 5 [2][3][4][5].…”

“…Perfluorinated 1-(2-or 4-ethylphenyl)-1,2-dihydrocyclobutabenzenes [3] and 1-or 2-alkyl-1-phenyl-1,2-dihydrocyclobutabenzenes [4,5] in SbF 5 undergo opening of the fourmembered ring, and the subsequent cyclization yields indan, fluorene, and anthracene derivatives. On the other hand, perfluoro(1-phenyl-1,2-dihydrocyclobutabenzene) having no perfluoroalkyl group, did not undergo skeletal transformations under analogous conditions [3].…”

“…No C 2 F 5 group migration in cationic species was observed previously. However, possible migration of CF 3 group via 1,2-shift was considered by us previously, e.g., in the isomerization of perfluoro(1-ethylindan) into perfluoro(1,1-dimethylindan) by the action of SbF 5 [9] and in the formation of perfluoro(9-ethyl-9-methyl-1,2,3,4-tetrahydrofluorene) by reaction of perfluoro(1-ethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride [4].…”

“…In addition, the structure of VII and XVI was proved by X-ray analysis, and specific features of their molecular structures were discussed in [1]. The 19 F NMR spectrum of VI was analyzed in comparison to the spectrum of perfluoro{4-[1-(2-methylphenyl)propylidene]cyclohexa-2,5-dien-1-one} whose structure was determined by X-ray analysis [4].…”

Formation of fluorene and anthracene derivatives in reactions of perfluorinated 1-alkyl-1-phenyl- and 1-alkyl-2-phenyl-1,2-dihydrocylobutabenzenes with antimony pentafluoride

“…Perfluoro[1-(2-or 4-ethylphenyl)-1,2-dihydrocyclobutabenzenes] [2] and perfluoro(1-ethyl-1-phenyl-1,2-dihydrocyclobutabenzene) [3] react with SbF 5 to give products of four-membered ring opening, which then undergo cyclization to anthracene or fluorene derivatives. On the other hand, no skeletal transformations of perfluoro(1-phenyl-1,2-dihydrocyclobutabenzene) occurs under analogous conditions [2].…”