Asymmetric Aza‐Morita–BaylisHillman Reaction of N‐Sulfonated Imines with Activated Olefins Catalyzed by Chiral Phosphine Lewis Bases Bearing Multiple Phenol Groups

Abstract

AbstractIn the aza‐Morita–BaylisHillman reaction of N‐sulfonated imines (N‐arylmethylidene‐4‐methylbenzenesulfonamides) with methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), and acrolein, we found that, through the use of catalytic amounts of chiral phosphine Lewis bases bearing multiple phenol groups, the corresponding adducts could be obtained in good yields with >90% ee at −20 °C or at room temperature in THF. The mechanism of this process was investigated by 31P NMR spectroscopic analysis. The phenoxide or the key enolate intermediate, which is stabilized by intramolecular hydrogen bonding with phenol groups, was observed by 31P NMR spectroscopy. Thus, the most effective bifunctional LBBA (Lewis base and Brønsted acid) phosphine‐Lewis base promoter system reported to date has been identified for such catalytic, asymmetric aza‐Morita–BaylisHillman reactions.