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Start date: 1999 × DDC: 540 × Type: Text × Publisher: Cambridge : RSC × Subject: Catalysis ×

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Now showing 1 - 4 of 4
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    Unprecedented selective homogeneous cobalt-catalysed reductive alkoxylation of cyclic imides under mild conditions
    (Cambridge : RSC, 2017) Cabrero-Antonino, Jose R.; Adam, Rosa; Papa, Veronica; Holsten, Mattes; Junge, Kathrin; Beller, Matthias
    The first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF4)2·6H2O/triphos (L1)] combination and no external additives are required. Using the optimal cobalt-system, the hydrogenation of the aromatic ring of the parent phthalimide is avoided and only one of the carbonyl groups is selectively functionalized. The resulting products, N- and aryl-ring substituted 3-alkoxy-2,3-dihydro-1H-isoindolin-1-one and N-substituted 3-alkoxy-pyrrolidin-2-one derivatives, are prepared under mild conditions in good to excellent isolated yields. Intramolecular reductive couplings can also be performed affording tricyclic compounds in a one-step process. The present protocol opens the way to the development of new base-metal processes for the straightforward synthesis of functionalized N-heterocyclic compounds of pharmaceutical and biological interest.
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    Palladium-catalyzed intermolecular transthioetherification of aryl halides with thioethers and thioesters
    (Cambridge : RSC, 2020) Li, Yahui; Bao, Gao; Wu, Xiao-Feng
    Functional group transfer reactions are an important synthetic tool in modern organic synthesis. Herein, we developed a new palladium-catalyzed intermolecular transthioetherification reaction of aryl halides with thioethers and thioesters. The synthetic utility and practicality of this catalytic protocol are demonstrated in a wide range of successful transformations (>70 examples). This catalytic protocol is applicable in carbonylative coupling processes as well, and the first example of carbonylative methylthioesterification of aryl halides has been achieved. Notably, this work also provides an approach to using natural products, such as methionine and selenomethionine, as the functional group sources. This journal is © The Royal Society of Chemistry.
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    Origins of high catalyst loading in copper(i)-catalysed Ullmann-Goldberg C-N coupling reactions
    (Cambridge : RSC, 2017) Sherborne, Grant J.; Adomeit, Sven; Menzel, Robert; Rabeah, Jabor; Brückner, Angelika; Fielding, Mark R.; Willans, Charlotte E.; Nguyen, Bao N.
    A mechanistic investigation of Ullmann-Goldberg reactions using soluble and partially soluble bases led to the identification of various pathways for catalyst deactivation through (i) product inhibition with amine products, (ii) by-product inhibition with inorganic halide salts, and (iii) ligand exchange by soluble carboxylate bases. The reactions using partially soluble inorganic bases showed variable induction periods, which are responsible for the reproducibility issues in these reactions. Surprisingly, more finely milled Cs2CO3 resulted in a longer induction period due to the higher concentration of the deprotonated amine/amide, leading to suppressed catalytic activity. These results have significant implications on future ligand development for the Ullmann-Goldberg reaction and on the solid form of the inorganic base as an important variable with mechanistic ramifications in many catalytic reactions.
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    Aldehydes and ketones influence reactivity and selectivity in nickel-catalysed Suzuki-Miyaura reactions
    (Cambridge : RSC, 2020) Cooper, Alasdair K.; Leonard, David K.; Bajo, Sonia; Burton, Paul M.; Nelson, David J.
    The energetically-favorable coordination of aldehydes and ketones-but not esters or amides-to Ni0 during Suzuki-Miyaura reactions can lead either to exquisite selectivity and enhanced reactivity, or to inhibition of the reaction. Aryl halides where the C-X bond is connected to the same π-system as an aldehyde or ketone undergo unexpectedly rapid oxidative addition to [Ni(COD)(dppf)] (1), and are selectively cross-coupled during competition reactions. When aldehydes and ketones are present in the form of exogenous additives, the cross-coupling reaction is inhibited to an extent that depends on the strength of the coordination of the pendant carbonyl group to Ni0. This work advances our understanding of how common functional groups interact with Ni0 catalysts and how these interactions affect workhorse catalytic reactions in academia and industry. This journal is © The Royal Society of Chemistry.