Photochemical isomerisation derivatives of decafluorocyclohexene and their reactions

Abstract

Perfluoro-(methylenecyclopentane) and -(1-methylcyclopentene), together with some higher-boiling compounds, have been obtained by the u.v.-irradiation of decafluorocyclohexene. Perfluoro-(methylenecyclopentane) underwent addition of chlorine and isomerisation to perfluoro-(1-methylcyclopentene), catalysed by fluoride ion; on treatment with sodium borohydride in bis-(2-methoxyethyl) ether it gave 1H-hexafluoro-2-methylcyclopentene, 3,3,4,4-tetrafluoro-1-trifluoromethylcyclopentene, and five polyfluoro-olefins as minor components. Both perfluoro-(methylenecyclopentane) and -(1-methylcyclopentene), on treatment with sodium iodide in acetone, afforded hexafluoro-1-iodo-2-trifluoromethylcyclopentene, which reacted with magnesium in ether to give a Grignard reagent, and with pentafluoroiodobenzene and copper bronze to give perfluoro-(2,2′-dimethylbicyclopent-1,1′-enyl) and hexafluoro-1-pentafluorophenyl-2-trifluoromethylcyclopentene. Perfluoro-(methylenecyclopentane) reacted with aluminium chloride in methyl iodide to give 1-(chlorodifluoromethyl)heptafluorocyclopentene, which, on treatment with sodium iodide in acetone, afforded 1-(difluoroiodomethyl)heptafluorocyclopentene. Both compounds could be dehalogenofluorinated to give perfluoro-(3-methylenecyclopentene), which added chlorine and underwent isomerisation, catalysed by fluoride ion, to perfluoro-1- and -2-methylcyclopentadiene. When heated, the former compound gave perfluoro-(1,4-dimethyltricyclo[5,2,1,0^2,6]deca-3,8-diene), a Diels–Alder dimer, and the latter gave a mixture of dimeric products. From the high-boiling products of the irradiation of decafluorocyclohexene, perfluoro-bicyclohex-1,1′-enyl, -1-cyclohexylcyclohexene, -1,1′-bicyclohexylidene, -1-(cyclohex-1-enyl)-1-methylcyclopentane, -bicyclohexyl, and -1-cyclohexyl-1-methylcyclopentane, were obtained.