Chiral Ionic Liquids Bearing O-Silylated α,α-Diphenyl (S)- or (R)-Prolinol Units: Recoverable Organocatalysts for Asymmetric Michael Addition of Nitroalkanes to α,β-Enals

Chiral ionic liquids bearing O‐silylated α,α‐diphenyl (S)‐ or (R)‐prolinol units tagged to the imidazolium cation were synthesized and their activity as catalysts in the Michael addition of nitroalkanes to α,β‐unsaturated aldehydes was evaluated. Respective (S) or (R) adducts were obtained in the reactions in high yields (up to 95 %) and with high enantioselectivity (up to 99 % ee). Remarkably, the immobilized organocatalysts could be used five times without any decrease in product yields or ee values. (R)‐Michael adducts could be easily transformed into the most active (R) enantiomers of medications Phenibut, Baclofen, and Rolipram for the treatment of CNS disorders. Ionic liquids with (S)‐ or (R)‐diphenylprolinol units were used as catalysts in the Michael addition of nitroalkanes to α,β‐enals. Adducts with the (S)‐ or (R) configuration were obtained in high yields (upto 95 %) and with high ee values (up to 99 %) The immobilized catalysts were used five times without a decrease in yield or ee values.