Isomerization of Halogenated Cyclopentene over a NH₄F Catalyst

The mechanism of the halogen-transfer isomerization of halogenated cyclopentene was investigated over a NH₄F catalyst in DMF. This catalytic system was to have the unique ability to isomerize halogenated cyclopentene selectively. The process of migration of the F atom in the 3-position on the C(sp³) atom to the 4-position on the C(sp³) atom is in chemical equilibrium, whereas the process of migration of the F atom in the 2-position on the C(sp²) atom to the 3-position on the C(sp³) atom is not. Therefore, halogenated cyclopentene containing fluorine on either the C(sp³) or C(sp²) atom could be prepared selectively in terms of the NH₄F catalyst.