Gas‐phase ambident reactivity of cyclic enolate anions

The gas‐phase reactions between cyclic enolate anions and unsaturated perfluorocarbon compounds were studied by Fourier transform ion cyclotron resonance. A correlation is observed between the experimental electron detachment threshold energies, the reaction selectivity and the ring size of the cyclic enolate anions. The results suggest that frontier orbital interactions play an important role in the course of the reactions of cyclic enolate anions, as has been shown previously for the reactions of acyclic enolate anions. In addition, the reaction selectivity of cyclic enolate anions may also be influenced by the charge distribution and by transannular interactions. In comparison with the acyclic enolate anions, the HOMO energy of the small cyclic enolate anions (C4–C5) has decreased and the carbanion character has increased, both of which favour reaction via carbon. The medium ring‐sized cycloketone enolate anions behave very similarly to their acyclic analogues, whereas for the larger ring‐sized cycloketone enolate anions (C8–C12) the reaction via the carbon nucleophilic centre gains importance as a result of the stabilization of the HOMO due to transannular interactions.