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 or acrolein in the presence of 0.1-1 mol% of a rhodium catalyst prepared in situ from RhH(CO)(PPh(3))(3) and a trans-chelating chiral diphosphine ligand (S,S)-(R,R)-PhTRAP in benzene at 3-5 degrees 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 alpha-methyl-alpha-amino acid.