On the mechanisms of acid-catalyzed enolization and hydrogen isotope exchange of cyclic ketones

The acid-catalyzed hydrogen isotope exchange of norcamphor 1 in DOAc–DCl–D2O is shown to follow the general theory (4) for exchange of a diastereotopic proton pair α to a carbonyl group. That is, the less reactive proton undergoes exchange via two channels. Through an analysis of a combination of the rate data for acid-catalyzed bromination and the pKBH+ values for a series of cyclic and bicyclic ketones, we establish that the reactivity order in the former is controlled by ketone basicity and not, as has been suggested previously, by angle strain developed in a very enol-like transition state.

On the mechanisms of acid-catalyzed enolization and hydrogen isotope exchange of cyclic ketones Journal Articles