Reactions involving fluoride ion. Part 25. A fluoride-ion-induced skeletal rearrangement

Abstract

Reaction of a perfluorocyclobutene trimer (2) with fluoride ion at room temperature gives a remarkable rearrangement to a seven-membered-ring compound (3). This cyclisation is formulated as an intramolecular displacement of fluoride, from a saturated site. The structure of (3) follows partly from pyrolysis studies, giving a series of sevenmembered-ring compounds (21)–(23) derived from (3) by loss of C₂F₄ and isomerisation.