Asymmetric Michael reaction of α-cyano carboxylates catalyzed by a rhodium complex with trans-chelating chiral diphosphine PhTRAP

Article abstract of DOI:10.1016/S0040-4020(01)89377-7

Asymmetric Michael reaction of 2-cyanopropionates with vinyl ketones or acrolein in the presence of 0.1-1 mol% of a rhodium catalyst prepared in situ from RhH(CO)(PPh₃)₃ and a trans-chelating chiral diphosphine ligand (S,S)- (R,R)-PhTRAP in benzene at 3-5 °C gave optically active Michael adducts with high enantiomeric excesses (83-93% ee) in high yields. The reaction of 2- cyanopropionate with methacrolein and crotonaldehyde proceeded somewhat slowly, giving diastereomer mixtures in moderate enantioselectivities but in low diastereoselectivities. The reaction of 2-cyanobutyrate and 2-cyano-3- methylbutyrate with acrolein gave corresponding Michael adducts with much lower enantiomeric excesses than that of 2-cyanopropionates. The Michael addition product from acrolein was converted into an optically active α- methyl-α-amino acid.