Enantioselective Construction of Spirocyclic Oxindoles via Tandem Michael/Michael Reactions Catalyzed by Multifunctional Quaternary Phosphonium Salt

The enantioselective construction of five-membered spirocyclic oxindoles via a double Michael cascade reaction is described by using dipeptide-based multifunctional quaternary phosphonium salt catalysts. The desired products were obtained in excellent yields (up to 94%) and good to high stereo-selectivities (up to >19:1 dr and 99% ee).