Fluoro-olefin chemistry. Part 12. Some reactions of 3,4-dihalogenotetrafluorocyclobutenes: a synthesis of perfluorocyclo-octatetraene

Abstract

Unsuccessful attempts have been made to dehalogenate 3,4-dichlorotetrafluorocyclobutene and 3-chlorotetrafluoro-4-iodocyclobutene. The dichlorocyclobutene yields an unstable complex (π-C₄F₄Cl₂)Fe(CO)₄ with Fe₂(CO)₉. Tetrafluoro-3,4-di-iodocyclobutene gives perfluorocyclo-octatetraene (58%) upon pyrolysis at 250 °C, and in addition to the cyclo-octatetraene (31%), perfluorostyrene (24%), and tetrafluoro-1,4-di-iodobuta-1,3-diene (37%) upon pyrolysis at 580 °C and 0.1 mmHg. With zinc dust, isomeric cyclobutenes are formed by fluorine migration, and the coupled product from copper bronze also results from fluorine migration. With phenylacetylene at 200 °C, 1,2,3,4-tetrafluorobiphenyl (12%) is obtained.