Polyfluorocyclopentadienes. Part IV. Reactions of perfluorocyclopentadiene with diethyl maleate and diethyl fumarate

Abstract

Thermal reaction of perfluorocyclopentadiene with diethyl maleate yields the Diels–Alder adduct diethyl-1,2,3,4,7,7-hexafluorobicyclo[2,2,1]hept-2-ene-cis-5,6-dicarboxylate (I); the corresponding trans-isomer (II) is formed with diethyl fumarate. Thus both reactions comply with the ‘cis’ principle formulated by Alder and Stein. Comparison of the ¹⁹F n.m.r. spectra of (I) and (II) suggests that the former compound possesses the endo-configuration. An improved preparation of perfluorocyclopentadiene is described.