Auto-Tandem Cooperative Catalysis Using Phosphine/Palladium: Reaction of Morita-Baylis-Hillman Carbonates and Allylic Alcohols

摘要

Auto-tandem catalysis (ATC), in which a single catalyst promotes two or more mechanistically different reactions in a cascade pattern, provides a powerful strategy to prepare complex products from simple starting materials. Reported here is an unprecedented auto-tandem cooperative catalysis (ATCC) for Morita-Baylis-Hillman carbonates from isatins and allylic carbonates using a simple Pd(PPh3)(4 )precursor. Dissociated phosphine generates phosphorus ylides and the Pd leads to pi-allylpalladiunz complexes, and they undergo a gamma-regioselective allylic-allylic alkylation reaction. Importantly, a cascade intramolecular Heck-type coupling proceeds to finally furnish spirooxindoles incorporating a 4-methylene-2-cyclopentene motif Experimental results indicate that both Pd and phosphine play crucial roles in the catalytic Heck reaction. In addition, the asymmetric versions with either a chiral phosphine or chiral auxiliary are explored, and moderate results are obtained.