Reactions involving fluoride ion. Part 31. Remarkable reactivity of perfluoro-bicyclobutylidene

Abstract

Perfluorobicyclobutylidene (3) readily forms cycloadducts with butadiene, cyclopentadiene, 6,6-dimethylfulvene and furan, whereas perfluoro-3,4-dimethylhex-2-ene (2) is unreactive under the same conditions. This marked difference in reactivity between (2) and (3) is attributed to angle strain in (3). Reaction of the alkene (3) with cyclohexa-1,3-diene yields 1H,1′H-perfluorobicyclobutyl (9) and benzene, by hydrogen transfer. The alkene (3) undergoes an ‘ene’ reaction with propene. Epoxides of perfluorobicyclobutylidene (3) and perfluorobicyclopentylidene (11) have been prepared; they both show high thermal stability and the latter epoxide fragments in the presence of fluoride ion to yield perfluorocyclopentene and perfluorocyciopentanone.