摘要:
New chiral nitroenamines 4a,b having (S)-2-t-butyldimethylsiloxymethylpyrrolidine as an auxiliary were found to be very effective for asymmetric nitroolefination of alpha-alkyl-gamma- and delta-lactones. The enantiomeric excess of the product increased remarkably in the reaction with gamma-lactones compared with previous nitroenamines 1a,b. A possible chelation model for the transition state of the asymmetric nitroolefination is discussed.