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A New Pyrrolidine-Based Catalyst for Nitro-Michael Additions
B. Tan, X. Zeng, Y. Lu, P. J. Chua, G. Zhong*
Nanyang Technological University, republic of Singapore
25 May 2009 (online)
Zhong and co-workers report the application of the new pyrrolidine-based organocatalyst 3 in the asymmetric Michael addition of six-membered cyclic ketones 1 to (hetero)aromatic nitroolefins 2 giving the corresponding Michael adducts 4 in high yields (87-99%) along with excellent diastereo- and enantioselectivities (98:2 to >99:1 dr, 96:4 to >99.5:0.5 er). The strong polar P=O group of catalyst 3 is attributed to play a significant role. As supported by DFT calculations, it likely orientates the nitro group for the stereoselective enamine addition via a strong H-bond mediated by water.