49. “Rearrangements Involving C₈H₈F-Cations of the Cage Type”
    Jefford, C. W.; Mareda, J.; Blaudzun, J.-P.; Burger, U.
    Helv. Chim. Acta 1982, 65, 2476-2480.

The homo-l, 4 adduct obtained from difluorocarbene and bicyclo [2.2.1]hepta-2, 5-diene (1) was treated successively with HCl, FSO₃H and SbF₅ in SO₂ClF at low temperature. The protic acids underwent electrophilic addition to the cyclopropane part of 1, giving the corresponding derivatives. However, in FSO₃H at − 50°, protonation of the gem-difluoro grouping also occurred to give the 2-fluoro-6-fluorosulfonylbicyclo [3.2.1]oct-2-en-3-yl cation. The reaction of 1 with SbF₅ at −78° led initially to the formation of the 2-fluorobicyclo [3.2.1 ]octa-2, 6-dien-4-yl cation, which rearranged to 4-fluorotricyclo [5.1.0.0^5,8]oct-3-en-2-yl cation at −40°. These rearrangements are discussed in the light of those expected for C₈H₈F square pyramidal cations.

DOI : 10.1002/hlca.19820650816 

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