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NHC Organocatalytic Formal LUMO Activation of α,β-Unsaturated Esters for Reaction with Enamides


  • We thank the Singapore National Research Foundation (NRF), the Singapore Economic Development Board (EDB), GlaxoSmithKline (GSK), and Nanyang Technological University (NTU) for generous financial support, and Dr. Y. Li and Dr. R. Ganguly (NTU) for X-ray crystal-structure analysis. LUMO=lowest unoccupied molecular orbital, NHC=N-heterocyclic carbene.


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An effective wake-up call: Stable α,β-unsaturated esters were activated by the addition of a chiral N-heterocyclic carbene (NHC) organocatalyst, and the resulting reactive Michael acceptor intermediates reacted with enamide nucleophiles to furnish optically pure products (see scheme; Ts=p-toluenesulfonyl). These products can be converted readily into bioactive δ-lactams, piperidines, and their derivatives.