Journal of the American Chemical Society, Vol.129, No.18, 5830-5830, 2007
A vaulted biaryl phosphoric acid-catalyzed reduction of alpha-imino esters: The highly enantioselective preparation of alpha-amino esters
A new method for the chiral phosphoric acid-catalyzed reduction of alpha-imino esters using Hantzsch ester is described. A series of 11 alpha-imino esters were evaluated, and it was shown that imino substrates derived from substituted aryl and alkyl keto esters could be reduced to the corresponding alpha-amino ester in excellent yield and in enantiomeric excesses from 94 to 99%. Catalyst loading was 5 mol % in each case, and the reactions were run with toluene as the solvent.