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A mutually compatible and cooperative combination of copper(I) triflate and bifunctional 9-amino-9-deoxyepicinchona-derived urea compounds for the enantioselective Conia-ene cyclization of alkyne-tethered beta-ketoester substrates is reported. The reaction is efficient, broad in scope, and easy to perform and allows access to chiral methylenecyclopentane products with high enantiocontrol. The transformation illustrates the concept of combining inactive precatalysts with inactive transition-metal-ion complexes in situ to reversibly create a catalytically active combination of the two.
Yang et al. (Mon,) studied this question.