Towards a complete account of the mechanism of hydrogen isotope exchange of diastereotopic protons of carbon acids. II. Acid- and base-catalyzed enolization of bicyclo[2.2.1]heptan-2-ones. Evidence for exchange by inversion

A study of acid- and base-catalyzed hydrogen isotope exchange of bicyclo[2.2.1]heptan-2-one (1a) and its 3-deuteriated analogs has been carried out. We find that the k exo /k endo ratio (658 ± 66) for deuteroxide-catalyzed H → D exchange of 1a at C-3 is 7.2 ± 1.5 times greater than the k exo /k endo ratio (91 ± 9) for hydroxide-catalyzed D → H exchange of 1b. For acid-catalyzed exchange in CH 3 COOD(H)–D(H)Cl the rate ratios are 156 ± 20 and 29 …