Pairing an iridium catalyst with a chiral amine let researchers direct the formation of two neighboring stereocenters during a specific reaction: the α-allylation of branched aldehydes. By changing catalyst configurations, the 2013 study reported access to all four possible stereoisomeric products.
What the catalyst pair does
The method brings together two chiral catalysts, each activating a different reaction partner. An iridium phosphoramidate catalyst activates a secondary allylic alcohol, while a chiral amine activates a branched aldehyde through an enamine. In the resulting α-allylation, the partners form a new carbon–carbon bond and two adjacent stereocenters.
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Because each catalyst influences stereochemistry on its own reaction partner, the pair can steer the configurations at both newly formed centers. This is the key idea behind the study’s enantio- and diastereodivergent approach: rather than relying on a single catalyst system to dictate both outcomes, researchers can select catalyst stereoisomers to reach different combinations.
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How catalyst choice changes the product
The report describes access to the four possible stereoisomers by choosing between catalyst stereoisomers. These are distinct three-dimensional arrangements of the same molecular connectivity. The result is useful when a chemist needs control over both the relative configuration of the two centers (diastereoselectivity) and the handedness of the product (enantioselectivity).
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That control is demonstrated for the studied combination of α-disubstituted, or branched, aldehydes and secondary allylic alcohols. It should not be read as a general rule for all aldehyde reactions, allylations, or dual-catalytic chemistry.
What selectivity the study reported
Chemistry World’s 2013 account says that many examples in the researchers’ explored structural range gave yields above 70%, more than a 20-fold excess of the desired diastereomer, and enantiomeric excess above 99%. These are reported results for many examined examples, not guaranteed performance for every substrate or set of reaction conditions. The account does not provide substrate-by-substrate figures in the summary, so those numbers should not be assigned to a particular reaction without consulting the paper’s experimental data.
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Why the result mattered—and what remains open
The work addressed a longstanding challenge in asymmetric synthesis: controlling more than one newly formed stereocenter while retaining the ability to choose their configurations. Erick M. Carreira, who led the study, described the goal as developing “fully stereodivergent” reaction processes. Eric Jacobsen of Harvard University called the idea of having different catalysts activate each substrate “a beautifully simple solution to a long-standing problem.”
The 2013 report presented the strategy as an advance and raised the question of whether it could apply to other reactions in organic chemistry. The available evidence establishes the original α-allylation result, but does not establish how widely the approach was adopted afterward or its current standing across the field.
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The primary paper is Simon Krautwald, David Sarlah, Michael A. Schafroth, and Erick M. Carreira, “Enantio- and diastereodivergent dual catalysis: α-allylation of branched aldehydes,” Science 340(6136), 1065–1068 (May 31, 2013). DOI: 10.1126/science.1237068. Chemistry World’s account of the findings and reported performance appeared in 2013: Catalyst duo exerts powerful stereocontrol.
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