Fluoro-olefins. Part VII. Some thermal Diels–Alder reactions of perfluorocyclohexa-1,3-diene

Abstract

Perfluorocyclohexa-1,3-diene acts as both a diene and a dienophile in its thermal reactions with cyclopentadiene (to give 1,7,8,9,10,10,11,11-octafluorotricyclo[5,2,2,0^2,6]undeca-3,8-diene and 2,3,4,5,5,6,6,7-octafluorotricyclo[6,2,1,0^2,7]undeca-3,9-diene) and cyclohexa-1,3-diene (to give 1,8,9,10,11,11,12,12- and 2,3,4,5,5,6,6,7-octafluorotricyclo[6,2,2,0^2,7]dodeca-3,9-diene), but when it is heated with perfluorocyclopentadiene only the dimer of the latter is obtained. Thermal reaction of perfluorocyclohexa-1,3-diene with N-allyltrifluoroacetamide gives a Diels–Alder adduct, N-(1,4,5,6,7,7,8,8-octafluorobicyclo[2,2,2]oct-5-en-2-ylmethyl)trifluoroacetamide; the corresponding amine, generated-via reaction of the amide with methanolic hydrogen chloride, slowly isomerises to 1,2,3,7,8,8,9,9-octafluoro-4-azatricyclo[4,3,1,0^3,7]decane, thus indicating that the original adduct is predominantly or even exclusively the endo-isomer.