2‐[(Imidazolylthio)methyl]pyrrolidine as a Trifunctional Organocatalyst for the Highly Asymmetric Michael Addition of Ketones to Nitroolefins

The direct asymmetric Michael addition of ketones to nitroolefins catalyzed by 2‐[(imidazol‐2‐ylthio)methyl]pyrrolidine, constructed from natural L‐proline and imidazolylthio platforms, with salicylic acid as a co‐catalyst has been developed to give the products in high yields (up to 95 %) and with excellent enantioselectivities (up to 99 % ee). The highly efficient catalytic performance may be attributed to the dual activation of the Michael substrates by the trifunctional organocatalysts and the co‐catalyst salicylic acid, leading to the formation of a stable transition state complex through the synergic effect of hydrogen‐bonding and electrostatic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)