Synthesis and fluorine NMR chemical shifts for a series of exo-3,3-difluorotricyclo[3.2.1.02,4]octyl derivatives: The Diels–Alder alternative to difluorocarbene additions

The Diels–Alder cycloaddition of 1,2-dihalo-3,3-difluorocyclopropenes 1 to a series of five-membered ring dienes stereoselectively provided the corresponding exo-2,4-dihalo-3,3-difluorotricyclo[3.2.1.02,4]oct-6-ene adducts. Removal of the C2, C4 halogens(bromine or chlorine) before or after saturation of the C6, C7 double bond afforded a variety of gem-difluorocyclopropyl derivatives in the analogous tricyclic manifold. The 19F and 1H NMR chemical shifts and coupling constants are listed for each of these tricyclic systems.