Highly Enantioselective Electrophilic α-Bromination of Enecarbamates: Chiral Phosphoric Acid and Calcium Phosphate Salt Catalysts

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.