Superparamagnetic Nanoparticle-Supported (S)-Diphenylprolinol Trimethylsilyl Ether as a Recyclable Catalyst for Asymmetric Michael Addition in Water

A new superparamagnetic nanoparticle-supported (S)-diphenylprolinol trimethylsilyl ether (Jorgensen-Hayashi catalyst) was synthesized and applied for the asymmetric Michael addition of aldehydes to nitroalkenes in water, which gives products in moderate to good yields (up to 96%), good enantioselectivity (up to 90% ee) and diastereoselectivities (up to 99:1). The immobilized catalyst could be easily separated from the reaction by an external magnet and recycled for four times without significant loss of catalytic efficiency.