Highly Enantioselective Electrophilic α-Bromination of Enecarbamates: Chiral Phosphoric Acid and Calcium Phosphate Salt Catalysts.
Résumé
Metal-free chiral phosphoric acids and chiral calcium phosphates both catalyze highly enantio- and diastereoselective electrophilic α-bromination of enecarbamates to provide an atom-economical synthesis of enantioenriched vicinal haloamines. Either enantiomer can be formed in good yield with excellent diastereo- and enantioselectivity simply by switching the catalyst from a phosphoric acid to its calcium salt.