Room temperature, solventless telomerization of isoprene with alcohols using (N-heterocyclic carbene)–palladium catalysts

Maluenda, Irene; Chen, Ming‐Tsz; Guest, Daniel; Roe, S. Mark; Turner, Michael L.; Navarro, Oscar

doi:10.1039/c5cy00058k

Cited by 23 publications

(8 citation statements)

References 27 publications

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“…Interestingly, only monotelomers of glycerol were detected, although the alkylation of some of the PEG could not be suppressed. In 2015, the Pd/NHC‐catalyzed telomerization of isoprene with different alcohols was reported using preformed cationic palladium complexes . High selectivities to head ‐ head ‐products with methanol can remarkably be shifted towards tail ‐ head ‐products if bulkier alcohols are used.…”

Section: 3‐dienesmentioning

confidence: 99%

The Telomerization of 1,3‐Dienes – A Reaction Grows Up

2019

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Telomerization is a versatile tool for synthesizing unsaturated ethers, amines and other molecules starting from 1,3‐dienes and respective nucleophiles. The homogeneously catalyzed reaction has been the subject of academic and industrial research for over 50 years, offering a broad variety of substrates, catalysts and process concepts. This Minireview presents the advances and developments in this field over the last decade. The focus was on the conversion of renewable resources, the synthesis of promising new products and the development of efficient process concepts to combine these.

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Section: 3‐dienesmentioning

confidence: 99%

The Telomerization of 1,3‐Dienes – A Reaction Grows Up

2019

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“…An open mechanistic question is whether binding of NEt 3 to the metal center inhibits catalysis by directly competing with alcohol for the binding sites or by promoting formation of off-cycle high-spin alcohol complexes. Binding of NEt 3 to transition metals has been reported in the literature by several research groups. − Chaudhuri et al demonstrated that NEt 3 has an inhibitory effect on the aerobic oxidation of alcohols by a Cu complex containing an iminosemiquinone ligand . A similar inhibiting behavior has been observed by Ozerov and Fan for catalytic coupling of acetonitrile with aldehydes by a Ni complex of a diarylamido-based PNP ligand with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base .…”

Section: Discussionmentioning

confidence: 99%

Role of High-Spin Species and Pendant Amines in Electrocatalytic Alcohol Oxidation by a Nickel Phosphine Complex

et al. 2022

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The development of active and efficient electrocatalysts for oxidation of alcohols using earth-abundant metals will aid progress toward a renewable energy economy. Here, we present a detailed mechanistic study of electrocatalytic benzyl alcohol oxidation by a molecular nickel complex containing pendant amines using a combination of kinetic studies, nuclear magnetic resonance spectroscopy, and density functional theory. The catalyst preferentially binds alcohol in a high-spin octahedral geometry, but this complex is not readily deprotonated by an exogenous base and inhibits catalysis. Dissociation of one or more solvent ligands returns the complex to a low-spin state that can be deprotonated. Kinetic modeling indicates that the off-cycle high-spin intermediate lowers the catalytic turnover frequency by a factor of 8, suggesting that substantial gains in activity can be attained by improvements to the catalyst coordination geometry. In a second finding, we demonstrate that the pendant amine of the catalyst only functions as a proton relay for the potential-determining step, oxidation of a nickel hydride intermediate, but does not have a substantial impact on the overall rate for oxidation of benzyl alcohol to benzaldehyde. This result contradicts the common expectation for pendant amines to participate in rate-limiting proton transfer reactions.

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“…Oxindole-based hemiterpenes and monoterpenes are a class of biologically active natural products. − However, the synthesis of these compounds through prenylation and geranylation of oxindoles encounters substantial hurdles and challenges. − First, the four sp 2 carbon atoms in isoprene have similar electronic properties and steric hindrance. As a result, there are six possible addition modes, resulting in a low regioselectivity during the reaction (Scheme a).…”

Section: Introductionmentioning

confidence: 99%

Theoretical Insight into the Palladium-Catalyzed Prenylation and Geranylation of Oxindoles with Isoprene

Wang,

Yang,

Liu

et al. 2024

Inorg. Chem.

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This work presents a comprehensive mechanistic study of the ligand-controlled palladium-catalyzed prenylation (with C5 added) and geranylation (with C10 added) reactions of oxindole with isoprene. The calculated results indicate that the prenylation with the bis-phosphine ligand and geranylation with the monophosphine ligand fundamentally share a common mechanism. This mechanism involves the formation of two crucial species: a η3-allyl-Pd(II) cation and an oxindole carbon anion. Furthermore, the reactions necessitate the assistance of a second oxindole molecule, which serves as a Brønsted acid, providing a proton to generate the oxindole nitrogen anion. The oxindole nitrogen anion then acts as a Brønsted base, abstracting a C–H proton from another oxindole molecule to form an oxindole carbon anion. These mechanistic details differ significantly from those proposed in the experimental work. The present calculations do not support the presence of the Pd–H species and the η3, η3-diallyl-Pd(II) intermediate, which were previously suggested in experiments. The theoretical results rationalize the experimental finding that the bis-phosphine ligand favors the prenylation of oxindole, while the monophosphine ligand enables the geranylation of oxindole.

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Room temperature, solventless telomerization of isoprene with alcohols using (N-heterocyclic carbene)–palladium catalysts

Abstract: The use of a custom-made palladium complex for the telomerisation of isoprene with alcohols under green conditions is described.

Cited by 23 publications

References 27 publications

The Telomerization of 1,3‐Dienes – A Reaction Grows Up

The Telomerization of 1,3‐Dienes – A Reaction Grows Up

Role of High-Spin Species and Pendant Amines in Electrocatalytic Alcohol Oxidation by a Nickel Phosphine Complex

Theoretical Insight into the Palladium-Catalyzed Prenylation and Geranylation of Oxindoles with Isoprene

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