Noyori Ligand as Organocatalyst

Significance

The present work reveals the mono-sulfonyl diamine Ts-DPEN 3 as an effective catalyst for the asymmetric Michael addition of ­cyclic β-keto ester 2 to aromatic nitroolefins 1. The corresponding Michael adducts 4 were obtained in good yields with moderate to good diastereo- and enantioselectivities. The authors propose the simultaneous activation of both reaction partners via multiple H-bonds as the catalytic reaction mode. However, alternative mechanisms, for example invoking enamine activation, may also be considered (see scheme).