ASYMMETRIC MICHAEL REACTION OF ALPHA-CYANO CARBOXYLATES CATALYZED BY A RHODIUM COMPLEX WITH TRANS-CHELATING CHIRAL DIPHOSPHINE PHTRAP

Asymmetric Michael reaction of 2-cyanopropionates with vinyl ketones o r acrolein in the presence of 0.1-1 mol% of a rhodium catalyst prepare d in situ from RhH(CO)(PPh(3))(3) and a trans-chelating chiral diphosp hine ligand (S,S)-(R,R)-PhTRAP in benzene at 3-5 degrees C gave optica lly active Michael adducts with high enantiomeric excesses (83-93% ee) in high yields. The reaction of 2-cyanopropionate with methacrolein a nd crotonaldehyde proceeded somewhat slowly, giving diastereomer mixtu res in moderate enantioselectivities but in low diastereoselectivities . The reaction of 2-cyanobutyrate and 2-cyano-3-methylbutyrate with ac rolein gave corresponding Michael adducts with much lower enantiomeric excesses than that of 2-cyanopropionates. The Michael addition produc t from acrolein was converted into an optically active alpha-methyl-al pha-amino acid.