Reactions involving fluoride ion. Part 23. Thermolytic defluorination of perfluoroalkenes in the synthesis of fluorinated dienes and cyclobutenes

Abstract

Passage of perfluoro-3,4-dimethylhex-3-ene over iron or platinum at elevated temperatures leads to defluorination and fragmentation, giving fluorinated dienes, e.g. perfluoro-2,3-dimethylbutadiene (over Pt) and perfluoro-3,4-dimethylhexa-2,4-diene (over Fe), together with other products. Similar reactions occur with other fluorinated alkenes and the variation between fragmentation and defluorination is rationalised on the basis of the metal used, etc. The fluoride induced reaction between perfluoropropene and perfluorobut-2-ene gives perfluoro-2,3-dimethylpent-2-ene.