Asymmetric Michael Addition of Oxindoles to Allenoate Catalyzed by N-Acyl Aminophosphine: Construction of Functionalized Oxindoles with Quaternary Stereogenic Center

A novel reaction between ethyl allenoate and oxindoles that enables the asymmetric synthesis of 3,3-bisubstituted oxindoles with our previously established bifunctional N-acyl aminophosphine catalysts is reported. These products bearing a chiral quaternary carbon center at the C-3 position of the oxindoles may have potential significance in the synthesis of related structures. The best performance of these processes provides adducts with 92% yield and 94% ee.