α-Quaternary Chiral Aldehydes from Styrenes, Allylic Alcohols, and Syngas via Multi-catalyst Relay Catalysis

Mimicking the way nature synthesizes organic molecules, multi-catalyst relay catalysis (MCRC), based on the seamless combination of a series of catalytic reactions, has emerged as a promising strategy for achieving ideal synthesis. In such systems, each step takes place orderly and sequentially. Taken as a whole, the entire process appears indistinguishable from a common one-step reaction but provides a means for extraordinary transformations. Here, we report a one-step transformation of styrenes, allylic alcohols, and syngas to alpha-quaternary chiral aldehydes in a multi-catalyst system consisting of a rhodium(I) complex, a palladium(0) complex, a chiral Bronsted acid catalyst, and an achiral amine (20-100 mol %). The cascade hydroformylation and asymmetric allylation reaction was realized with high yields (up to 98%) and high enantioselectivities (up to 99% ee) under mild conditions (1 bar of syngas).