Efficient Recovery and Reuse of an Immobilized Peptidic Organocatalyst

Readily reusable immobilized organocatalysts are important from a practical, economic, and environmental viewpoint. However, their successful development has proven challenging and only limited reaction and recovery cycles have been achieved. We report an extraordinarily robust resin-bound tripeptidic organocatalyst that can be readily reused for at least 30 reaction and recovery cycles without loss in catalytic activity or stereoselectivity. The immobilized catalyst can be directly reused for conjugate addition reactions between aldehydes and nitroolefins after a simple filtration from the reaction products. The catalytic efficiency and chemoselectivity of the immobilized peptidic catalysts is so high that a broad range of gamma-nitroaldehydes were isolated easily after filtration and removal of all volatiles in quantitative yields, excellent diastereoselectivities and enantioselectivities and, most remarkably, perfect analytical purities. The ease of handling allows for a facile scale-up of reactions catalyzed by the immobilized peptidic catalyst. In addition, the results provide a guide for the further development of immobilized organocatalysts.