Identifying palladium culprits in amine catalysis

Avanthay, Mickaël; Bedford, Robin B.; Begg, Callum; Böse, Dietrich; Clayden, Jonathan; Davis, Sean A.; Eloi, Jean‐Charles; Goryunov, Georgy P.; Hartung, Ingo V.; Heeley, Joseph; Khaikin, Kirill A.; Kitching, Matthew O.; Krieger, Johannes; Kulyabin, Pavel S.; Lennox, Alastair J. J.; Nolla-Saltiel, Roberto; Pridmore, Natalie E.; Rowsell, Benjamin J. S.; Sparkes, Hazel A.; Uborsky, Dmitry V.; Voskoboynikov, Alexander Z.; Walsh, Mark P.; Wilkinson, Harry J.

doi:10.1038/s41929-021-00710-1

Cited by 28 publications

(21 citation statements)

References 11 publications

(22 reference statements)

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“…The issue of trace Pd being carried through an amine ligand synthesis has been highlighted, − leading to the retraction of a high-profile paper describing an amine-catalyzed SMCC reaction of aryl halides and arylboronic acids . The consideration of the ppm levels of Pd in any given system, as highlighted in this Review, arguably allows one to critically evaluate whether any predicted “Pd-free” methodology might operate at low ppm Pd levels.…”

Section: Discussionmentioning

confidence: 99%

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

Horbaczewskyj

Fairlamb

2022

Org. Process Res. Dev.

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This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of “ppm level” palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether “ppm level” palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low “ppm levels” of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.

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Section: Discussionmentioning

confidence: 99%

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

Horbaczewskyj

Fairlamb

2022

Org. Process Res. Dev.

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“…By February 2021, Tolnai and Novák had reported 6 that trace palladium impurities left over after making the amine catalyst were the true catalyst for the reaction. In March 2021, Bedford and his colleagues reported 7 the exact palladium species involved -a compound that chemists already knew to be a highly active catalyst (see 'Carbon coupling').…”

Section: Setting the Record Straightmentioning

confidence: 99%

Why chemists can’t quit palladium

Remmel¹

2022

Nature

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“…Likewise, catalysis can lead to unexpected amplifications [12–14] . Only recently, reports of an unforeseen amine‐catalyzed cross‐coupling reaction—which turned out to be catalyzed by ppm traces of palladium in the amine catalyst—stimulated research on the effect of trace amounts of metals in catalytic reactions [15–18] . Such examples highlight how the highly efficient catalysis of an impurity can easily outperform the intended catalyst and thus lead to unexpected results.…”

Section: “Real” Effect or Error—a Selection Of Our Experiencesmentioning

confidence: 99%

“…[12][13][14] Only recently, reports of an unforeseen amine-catalyzed cross-coupling reaction-which turned out to be catalyzed by ppm traces of palladium in the amine catalyst-stimulated research on the effect of trace amounts of metals in catalytic reactions. [15][16][17][18] Such examples highlight how the highly efficient catalysis of an impurity can easily outperform the intended catalyst and thus lead to unexpected results. Crystallization and catalysis are disciplines that have been explored by organic chemists for more than a century, providing in-depth understanding of underlying effects that can bias processes.…”

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confidence: 99%

How Subtle Changes Can Make a Difference: Reproducibility in Complex Supramolecular Systems

et al. 2022

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The desire to construct complex molecular systems is driven by the need for technological (r)evolution and our intrinsic curiosity to comprehend the origin of life. Supramolecular chemists tackle this challenge by combining covalent and noncovalent reactions leading to multicomponent systems with emerging complexity. However, this synthetic strategy often coincides with difficult preparation protocols and a narrow window of suitable conditions. Here, we report on unsuspected observations of our group that highlight the impact of subtle "irregularities" on supramolecular systems. Based on the effects of pathway complexity, minute amounts of water in organic solvents or small impurities in the supramolecular building block, we discuss potential pitfalls in the study of complex systems. This article is intended to draw attention to often overlooked details and to initiate an open discussion on the importance of reporting experimental details to increase reproducibility in supramolecular chemistry.

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Identifying palladium culprits in amine catalysis

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Cited by 28 publications

References 11 publications

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

Why chemists can’t quit palladium

How Subtle Changes Can Make a Difference: Reproducibility in Complex Supramolecular Systems

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