Polyfluoro-compounds based on the cycloheptane ring system. Part 6. Bicyclic compounds derived from nonafluorocyclohepta-1, 3-dienes and from octafluorocyclohepta-1, 3, 5-triene

1H-, 2H-, and 5H- Nonafluoro- and 1H,4H-octafluoro-cyclohepta-1,3 diene afforded the corresponding H-substituted polyfluorobicyclo(3, 2, 0)- hept-6-enes by cross-ring bond formation between positions 1 and 4. Octafluorocyclohepta-1, 3, 5-triene similarly gave octafluorobicyclo- (3,2,0)hepta-2,6-diene. By passage over cobalt(III) fluoride at 100°C, the 1H-bicyclo-6-ene gave 1H-undecafluorobicyclo(3, 2, 0)heptane and thence the corresponding fluorocarbon. The bridgehead hydrogen of the 1H- bicyclo-ane was sufficiently acidic to exchange for deuterium with deuterium oxide, alone or containing some potassium hydroxide, but longer exposure to aqueous potash gave decafluorobicyclo(3, 2, 0)hept-1(5)-ene. This was oxidised by potassium permanganate in acetone to give decafluoro-1, 5- dihydroxy-8-oxabicyclo(3, 2, 1)octane (hydrated), which underwent methylation by diazomethane to the corresponding 1,5-dimethoxy-compound. A Diels-Alder reaction between ethylene and 1H-nonafluorocyclohepta-1, 3- diene afforded 1H,8H,8H,9H,9H-nonafluoro-bicyclo(3,2,2)non-6-ene. Cobalt (III) fluoride at 300°C converted this principally to 1H-pentadecafluoro- bicyclo(3,2,2)nonane. The bridgehead hydrogen of this was exchanged for deuterium using deuterium oxide alone or containing potassium hydroxide. However, dehydrofluorination occurred with bases, though an olefin could not be isolated.