A Highly Diastereoselective Decarboxylative Mannich Reaction of β-Keto Acids with Optically Active N-Sulfinyl α-Imino Esters

A range of protected γ-oxo-α-amino esters have been prepared in a highly regio- and stereoselective manner through the decarboxylative Mannich reaction of β-keto acids with optically active N-tert-butanesulfinyl α-imino esters in the presence of 3 mol % La(OTf)(3) or 5 mol % Y(OTf)(3) at 20 °C. Preliminary mechanistic studies indicate that the reaction proceeds through imine addition followed by decarboxylation.