This report describes the synthesis of eight ferrocene derivatives of squaramide-
or thiourea- based bifunctional catalysts containing cinchona alkaloid moieties. A
stepwise sequential route was used to assemble the various components of these ferrocene
derivatives. The resulting bifunctional catalysts were used successfully in asymmetric
Michael additions of 1,3-dicarbonyl compounds to β-nitrostyrenes. The corresponding
products were obtained in high yields and in good to excellent enantioselectivities
and diastereoselectivities under mild conditions by using 1 mol% of the catalyst.
Key words
Michael additions - asymmetric catalysis - ferrocenes - alkaloids - nitro compounds
- dicarbonyl compounds