Asymmetric aldol reactions catalyzed by a novel polystyrene-immobilized proline derivative occur in short reaction times with excellent diastereo- and enantioselectivity. The catalyst can be recovered by simple filtration and shows very high reusability. The high activity depicted by the supported catalyst and its chemical and mechanical stability have allowed its application in packed-bed reactors for continuous flow processing. This system can produce enantio- and diastereomerically pure aldol adducts under continuous flow conditions with a residence time of 26?min. Furthermore, the reactor allowed processing of four different aldol products in sequence without any decrease in both catalytic activity and optical purity. The effective catalyst loading could be reduced to 1.6 % (six-fold reduction of catalyst loading compared to the corresponding batch process).
A solid-supported organocatalyst for continuous-flow enantioselective Aldol reactions
ChemSusChem 2012, 5, 320-325.
*One of the most cited among those published in 2012 or 2013