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.