Chiral Phosphine Lewis Bases Catalyzed Asymmetric aza-Baylis-Hillman Reaction of N-Sulfonated (mines with Activated Olefins

摘要

In the aza-Baylis-Hillman reaction of N-sulfonated imines (N-arylmethylidene-4-methylben-zenesulfonamides and others) with methyl vinyl ketone,ethyl vinyl ketone,and acrolein,we found that,in the presence of a catalytic amount of chiral phosphine Lewis base such as (R)-2'-diphenylphosphanyl-[1,1']binaphthalenyl-2-ol LB1 (10 mol %) and molecular sieve 4A,the corresponding aza-Baylis-Hillman adducts could be obtained in good yields with good to high ee (70-95% ee) at low temperature (approx -30 to -20 deg C) or at room temperature in THF,respectively.In CH_2CI_2 upon heating at 40 deg C,the aza-Baylis-Hillman reaction of N-sulfonated imines with phenyl acrylate or naphthyl acrylate gave the adducts in good to high yields (60-97%) with moderate ee (52-77%).The mechanistic insight has been investigated by ~(31)P and ~1H NMR spectroscopic measurements.The key enolate intermediate,which has been stabilized by intramolecular hydrogen bonding,has been observed by ~(31)P and ~1H NMR spectroscopy.An effective bifunctional Lewis base and Bronsted acid phosphine Lewis base system has been disclosed in this catalytic,asymmetric aza-Baylis-Hillman reaction.