Six-at-Once Dedeuteration of Acetone-d6 in the Presence of 3-exo--2-exo-norbornanamine

Article abstract of DOI:10.1021/jo00169a039

3-exo-<(Dimethylamino)methyl>-2-exo-norbornanamine (2) was prepared and used as a catalyst in aqueous solution at 35 degC for the dedeuteration of acetone-d₆.Monoprotonated 2 acts as an effective catalyst by transforming the ketone to an iminium ion and then using its dimethylamino group to dedeuterate the iminium ion by internal basic catalysis.At pH 9.95 the most common result of iminium-ion formation is the exchange of all six deuterium atoms.This requires a mechanism for cis-trans isomerization of the intermediate iminium ion.The gem-diamine mechanism proposed earlier for iminium ions derived from cyclopentanone helps explain why 2 gives six-at-once exchange while some rather similar diamines do not.The kinetics of iminium-ion formation from 2 and acetone were studied by the hydroxylamine-capture technique.The rates of iminium-ion formation thus obtained are reasonably consistent with those obtained in the deuterium exchange experiments.