1170145-01-3Relevant academic research and scientific papers
Mechanistic investigations into the enantioselective Conia-ene reaction catalyzed by cinchona-derived amino urea pre-catalysts and CuI
Sladojevich, Filippo,Fuentes De Arriba, ángel L.,Ortín, Irene,Yang, Ting,Ferrali, Alessandro,Paton, Robert S.,Dixon, Darren J.
, p. 14286 - 14295 (2015/03/30)
The enantioselective Coniaene cyclization of alkyne-tethered β-ketoesters is efficiently catalyzed by the combination of cinchona-derived amino-urea pre-catalysts and copper(I) salts. The reaction scope is broad and a series of substrates can be efficiently cyclized with high yields and enantioselectivities. Herein, we present a detailed mechanistic study based on experimental considerations and quantum mechanical calculations. Several variables, such as the nature of the organic pre-catalyst and the metal-ion source, have been thoroughly investigated. Kinetic studies, as well as kinetic isotope effects and deuterium labeling experiments have been used to gain further insights into the mechanism and prove the cooperative nature of the catalytic system. Our studies suggest that the rate-limiting step for the reaction involves the β-ketoester deprotonation and that the active species responsible for the enantiodeterming step is monomeric in amino-urea pre-catalyst. Computational studies provide a quantitative understanding of the observed stereoinduction and identify hydrogen bonding from the urea group as a crucial factor in determining the observed enantioselectivity.
Bronsted base/Lewis acid cooperative catalysis in the enantioselective Conia-ene reaction
Yang, Ting,Ferrali, Alessandro,Sladojevich, Filippo,Campbell, Leonie,Dixon, Darren J.
supporting information; experimental part, p. 9140 - 9141 (2009/12/06)
(Chemical Equation Presented) 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 β-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.
