E,Z-Stereodivergent synthesis of N-tosyl α,β-dehydroamino esters via a Mukaiyama-Michael addition

The stereodivergent synthesis of N-tosyl α,β-dehydroamino esters via a Mukaiyama-Michael addition is reported. The reaction of silylketene acetals with N-tosylimines derived from β,γ-unsaturated α-keto esters in dichloromethane provided the corresponding (Z)-α,β-dehydroamino esters while the (E)-isomers were obtained when the reaction was carried out in the presence of 10 mol% copper(II) triflate.