Abstract 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 ...