TfNH2 as Achiral Hydrogen-Bond Donor Additive to Enhance the Selectivity of a Transition Metal Catalyzed Reaction. Highly Enantio- and Diastereoselective Rhodium-Catalyzed Cyclopropanation of Alkenes Using α-Cyano Diazoacetamide
Journal of the American Chemical Society2009Vol. 131(20), pp. 6970–6972
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Abstract
A highly stereoselective (up to 98% ee and 99:1 dr) Rh(II)-catalyzed formation of nitrile-substituted cyclopropanes is described. Alpha-cyano diazoacetamide reagents react with a variety of mono- and disubstituted olefins in good yields and excellent enantio- and diastereocontrol. Less reactive substrates, such as aliphatic olefins, also undergo the reaction. This new methodology features the unprecedented use of an achiral hydrogen-bond donor additive to enhance the selectivity and exploits the powerful trans-directing ability of amides solving the diastereocontrol issue of the formation of substituted 1-cyanocyclopropane-1-carboxy derivatives.