Heterobimetallic Zinc/Strontium Catalysis: Z / E -Selective Asymmetric Conjugate Addition of 3-Acetoxy-2-oxindoles to Alkynones.

A chiral Zn-Sr heterobimetallic catalyst system generated in situ has been developed for the first highly Z / E -selective asymmetric conjugate addition of 3-acetoxy-2-oxindoles to alkynones. Both terminal alkynones and nonterminal alkynones could be applied to the heterobimetallic catalytic system. The corresponding 3-alkenyl-3-acyloxy-2-oxindoles were obtained in moderate to excellent yields (55-99%) with high E : Z ratios (8:1-30:1) and high enantioselectivities (86-99% ee).