Bifunctional Quaternary Ammonium Salts Catalyzed Stereoselective Conjugate Addition of Oxindoles to Electron-Deficient β-Haloalkenes.

A highly Z-selective asymmetric conjugate addition of 3-substituted oxindoles to β-haloalkene ketones/esters catalyzed by readily available chiral bifunctional quaternary ammonium salts is reported. This reaction provides efficient access to a range of 2-oxoindole derivatives bearing a thermodynamically unstable Z-olefin structure and a chiral quaternary carbon center in high yields (up to 90%) and with good to high stereoselectivities (up to >19:1 Z/E and 91% ee) under mild conditions.