Efficient, Enantioselective Iminium Catalysis with an Immobilized, Recyclable Diarylprolinol Silyl Ether Catalyst

A highly efficient approach for the synthesis, application, and recycling of immobilized diarylprolinol silyl ethers was developed. The MeOPEG-supported Jørgensen-Hayashi catalyst provides unchanged reactivity and selectivity as compared to the homogeneous catalyst, as demonstrated for the Michael addition of nitromethane to alpha,beta-unsaturated aldehydes via iminium activation. In addition, the immobilization allows for a simple, column-free isolation of pure, sensitive aldehyde products and therefore may be useful for application in more complicated syntheses.