Highly efficient asymmetric amination of β-keto esters catalyzed by chiral quaternary ammonium bromides

A highly efficient asymmetric amination of β-keto esters was achieved under phase transfer conditions using chiral quaternary ammonium bromide as a catalyst. The amination products were obtained in quantitative yields with up to 97% ee. One of the amination products represents a key intermediate for the preparation of aldose reductase inhibitor AS-3201.