Synthesis of 1-iodo- and 1,2-di-iodo-perfluorocyclo-olefins and reductive coupling of the latter in the presence of copper bronze

Abstract

Decafluorocyclohexene, octafluorocyclopentene, 1-chloroheptafluorocyclopentene, and hexafluorocyclobutene reacted with sodium iodide in dimethylformamide to give nonafluoro-1-iodocyclohexene (in low yield), heptafluoro-1-iodo- and hexafluoro-1,2-di-iodo-cyclopentene, 1-chlorohexafluoro-2-iodocyclopentene, and tetrafluoro-1,2-di-iodocyclobutene with several minor products, respectively. Both hexafluoro-1,2-di-iodocyclopentene and tetrafluoro-1,2-di-iodocyclobutene underwent reductive coupling reactions when heated with copper bronze. The former compound afforded perfluoro(dodecahydrotetracyclopentenocyclo-octene), perfluoro(octahydrotricyclo-pentenobenzene), and small amounts of 3,3,3′,3′,3″,3″,4,4,4′,4′,4″,4″,5,5,5′,5′,5″,5″-octadecafluoro-2-iodo-1,1′:2′,1″-tercyclopentene and dodecafluoro-2,2′-di-iodo-1,1′-bicyclopentene; both the major products resisted oxidation but, on treatment with potassium hydroxide in methanol, the cyclo-octatetraene gave a complex mixture, whereas the tricyclopentenobenzene gave the 1,1-dimethoxy-derivative, which was hydrolysed by sulphuric acid to give the 1-ketone. Tetrafluoro-1,2-di-iodocyclobutene afforded perfluoro(hexahydrotricyclo-butenobenzene), octafluoro-2,2′-di-iodo-1,1′-bicyclobutene, and dodecafluoro-2,2″-di-iodo-1,1′:2′,1″-tercyclobutene. When heated with copper bronze, the bicyclobutene decomposed, whereas the tercyclobutene gave the hexahydrotricyclobutenobenzene. This reacted with potassium hydroxide in methanol to give the 1,1-dimethyoxy-derivative, which, on treatment with sulphuric acid, gave the 1-ketone.