A Vaulted Biaryl Phosphoric Acid-Catalyzed Reduction of α-Imino Esters: The Highly Enantioselective Preparation of α-Amino Esters
作者:Guilong Li、Yuxue Liang、Jon C. Antilla
DOI:10.1021/ja070519w
日期:2007.5.1
A new method for the chiral phosphoric acid-catalyzedreduction of α-iminoesters using Hantzsch ester is described. A series of 11 α-iminoesters were evaluated, and it was shown that imino substrates derived from substituted aryl and alkyl keto esters could be reduced to the corresponding α-amino ester in excellent yield and in enantiomeric excesses from 94 to 99%. Catalyst loading was 5 mol % in
Tris(trimethylsilyl)aluminum was found to be a good chemoselective reducing reagent for alpha-imino esters to give alpha-amino esters in good yields. Application to the reduction of 3,5-disubstituted 5,6-dihyro-2H-1,4-oxazine2-ones realized a stereoselective conversion into cis-3,5-disubstituted morpholine-2-ones.