Diastereo- and enantioselective conjugate addition of α-keto esters to nitroalkenes: Complete switch in the enantioselectivity by tuning the metal center or rigidity of the ligand

A series of efficient catalytic systems has been developed to control the dual enantioselectivity of the conjugate addition of α-keto esters to nitroalkenes. The use of the chiral diamine (1S,1’S)-1,1′-biisoindoline as a chiral ligand with either (Cu(OAc)2·H2O or Ni(OAc)2·4H2O as the catalyst provide facile access to the respective enantiomers resulting from the conjugate addition reaction with high levels of enantioselectivity (94% ee vs 93% ee). Furthermore, the use of Cu(OAc)2·H2O as the metal center allowed the enantioselectivity of the conjugate addition reaction to be switched through the tuning of the rigidity of the chiral diamine ligand (94% ee vs 94% ee).

Graphical AbstractThe dual enantioselectivity for the conjugate addition of α-keto esters to nitroalkenes has been controlled through the development of an efficient series of catalytic systems. Both enantiomers of the addition products were obtained in good yields with high enantioselectivities by tuning the rigidity of the chiral ligand or metal center.Figure optionsDownload as PowerPoint slide