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Issue 5, 2013
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Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

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Abstract

The direct asymmetric conjugate addition of α-cyanoacetates to enones generating densely functionalized α-amino acid precursors with adjacent quaternary and tertiary stereocenters is described comparing mono- and bis-palladacycle catalysts. This edge article features the complementary value of mono- and bimetallic catalysis in a case study using related catalyst systems. Different major diastereomers of the 1,4-addition products are formed by the use of the planar chiral mono- and bimetallic catalyst systems and provide access to epimeric amino acid derivatives. Both catalyst types require the use of a Brønsted acid (HOAc) as a co-catalyst to avoid an undesired β-hydride elimination. Kinetic studies show that the C–C bond forming step takes place almost instantaneously with the bis-palladium complex after productive substrate coordination. This extraordinarily high reactivity for an elementary step generating a sterically demanding linkage of a quaternary and a tertiary stereocenter stresses the cooperativity of both metal centers.

Graphical abstract: Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

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Article information


Submitted
12 Feb 2013
Accepted
13 Mar 2013
First published
22 Mar 2013

Chem. Sci., 2013,4, 2218-2233
Article type
Edge Article

Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

S. H. Eitel, S. Jautze, W. Frey and R. Peters, Chem. Sci., 2013, 4, 2218
DOI: 10.1039/C3SC50419K

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