Electronic and bite angle effects in catalytic C–O bond cleavage of a lignin model compound using ruthenium Xantphos complexes

Shaw, Luke; Somisara, D. M. Upulani K.; How, Rebecca C.; Westwood, Nicholas J.; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.; Kamer, Paul C. J.

doi:10.1039/c6cy00518g

Cited by 10 publications

(2 citation statements)

References 54 publications

(6 reference statements)

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“…As is well-known, ligand participation can promote and regulate organometallic catalysis. , In 2017, Kamer studied the ligand bite angle and electronic effects on the C β –OAr bond cleavage of the β-O-4 models over the Ru–diphosphine catalysts. It was observed that increasing the σ-donor capacity of the ligands can enhance substrate conversion.…”

Section: Organic Molecular Intermediatesmentioning

confidence: 99%

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

et al. 2023

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Lignin, as a precious resource given to mankind by nature with abundant functional aromatic structures, has drawn much attention in the recent decade from academia to industry worldwide, aiming at harvesting aromatic compounds from this abundant and renewable natural polymer resource. How to efficiently depolymerize lignin to easy-to-handle aromatic monomers is the precondition of lignin utilization. Many strategies/methods have been developed to effectively degrade lignin into monomers, such as the traditional methods of pyrolysis, gasification, liquid-phase reforming, solvolysis, chemical oxidation, hydrogenation, reduction, acidolysis, alkaline hydrolysis, alcoholysis, as well as the newly developed redox-neutral process, biocatalysis, and combinatorial strategies. Therefore, there is a strong demand to systemically summarize these developed strategies and methods and reveal the internal transformation principles of the lignin. Focusing on the topic of lignin depolymerization to aromatic chemicals, this review reorganizes and categorizes the strategies/methods according to their mechanisms, orbiting the center of critical intermediates during the lignin linkage transformation, which includes the critical anionic intermediates, cationic intermediates, organometallic intermediates, organic molecular intermediates, aryl cation radical intermediates, and neutral radical intermediates. The corresponding introduction involves the generation and the transformation chemistry of the critical intermediates via the corresponding C–H/O–H/C–C/C–O chemical bond transformations, leading to the cleavage of the C–C/C–O linkage bonds. Accompanying the brief introduction of lignin chemistry and the final concluding remarks and perspectives on lignin depolymerization, this review aims to provide a current research process of lignin depolymerization, which may provide useful suggestions for this vigorous research field.

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Section: Organic Molecular Intermediatesmentioning

confidence: 99%

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

et al. 2023

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“…They found, using model compounds, that the γ-hydroxy group in the native lignin β-O-4 motif A chelates to the ruthenium-Xantphos complex, trapping and thus deactivating the ruthenium catalyst (Figure b). Since the publication by Bergman and Ellman in 2010, many catalytic systems were developed that can catalyze the same depolymerization reaction sequence on the structurally simplified C2-β-O-4 model compounds representing β-O-4 motif B, − but none of these have been reported to be able to effectively depolymerize lignin.…”

Section: Introductionmentioning

confidence: 99%

Sequential Catalytic Modification of the Lignin α-Ethoxylated β-O-4 Motif To Facilitate C–O Bond Cleavage by Ruthenium-Xantphos Catalyzed Hydrogen Transfer

Zhang

Lahive

Zijlstra

et al. 2019

ACS Sustainable Chem. Eng.

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Lignin is an abundant natural biopolymer that has the potential to act as a renewable feedstock for valuable aromatic compounds via selective catalytic depolymerization. In recent years, elegant, mild, catalytic hydrogen neutral C–O bond cleavage methodologies have been developed on model compounds yielding acetophenone derivatives. However, none of these have been reported to be effective once applied to lignin. One of the reasons for this is the highly functionalized nature of the native lignin β-O-4 motif, which is often not taken into account in the β-O-4 model compounds used for methodology development. In this work, we demonstrate the development of a stepwise modification protocol on lignin β-O-4 model compounds to overall yield a partially defunctionalized β-O-4 motif. This was achieved by making use of an α-ethoxylated β-O-4 motif that is readily available from ethanosolv extraction of lignocellulosic biomass. This specific motif allowed us to apply selective copper catalyzed aerobic oxidation and subsequent rhodium catalyzed decarbonylation of the primary hydroxyl group in the γ position. The obtained partially defunctionalized β-O-4 lignin motif allowed effective homogeneous ruthenium catalyzed hydrogen neutral C–O bond cleavage (>99% of 3,4-dimethoxyacetophenone and >99% of guaiacol). The stepwise modification strategy was extended to walnut ethanosolv lignin, demonstrating that the specific structural motifs are accessible from such a readily available lignin. Overall, this work illustrates that the structure of lignin can be strategically modified to allow access to otherwise inaccessible specific aromatic compounds via selective depolymerization methodologies.

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Lignin Linkages Cleavage Beginning with C _α –H, C _α –OH, or C _α O–H Bond Non‐ionized Activation

2022

Lignin Conversion Catalysis

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Electronic and bite angle effects in catalytic C–O bond cleavage of a lignin model compound using ruthenium Xantphos complexes

Abstract: Bite angle and electronic effects on the ruthenium–diphosphine catalysed ether bond cleavage of the lignin β-O-4 model compound 2-phenoxy-1-phenylethanol were tested.

Cited by 10 publications

References 54 publications

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

Sequential Catalytic Modification of the Lignin α-Ethoxylated β-O-4 Motif To Facilitate C–O Bond Cleavage by Ruthenium-Xantphos Catalyzed Hydrogen Transfer

Lignin Linkages Cleavage Beginning with C _α –H, C _α –OH, or C _α O–H Bond Non‐ionized Activation

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Electronic and bite angle effects in catalytic C–O bond cleavage of a lignin model compound using ruthenium Xantphos complexes

Abstract: Bite angle and electronic effects on the ruthenium–diphosphine catalysed ether bond cleavage of the lignin β-O-4 model compound 2-phenoxy-1-phenylethanol were tested.

Cited by 10 publications

References 54 publications

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

Sequential Catalytic Modification of the Lignin α-Ethoxylated β-O-4 Motif To Facilitate C–O Bond Cleavage by Ruthenium-Xantphos Catalyzed Hydrogen Transfer

Lignin Linkages Cleavage Beginning with C α –H, C α –OH, or C α O–H Bond Non‐ionized Activation

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Lignin Linkages Cleavage Beginning with C _α –H, C _α –OH, or C _α O–H Bond Non‐ionized Activation