Chemo‐ and Regioselective Hydrogenolysis of Diaryl Ether C−O Bonds by a Robust Heterogeneous Ni/C Catalyst: Applications to the Cleavage of Complex Lignin‐Related Fragments

Gao, Fang; Webb, Jonathan D.; Hartwig, John F.

doi:10.1002/anie.201509133

Cited by 138 publications

(80 citation statements)

References 61 publications

(22 reference statements)

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“…However, this catalyst showed a low activity toward diaryl ethers with highly electron‐rich CO bonds and multiple substituents that mimic those in lignin. A heterogeneous Ni/C catalyst derived from the deposition of Ni(COD) 2 on activated carbon effectively catalyzed such diaryl ethers to aromatics . In these cases, a strong base was needed to obtain high selectivity toward the aromatics; otherwise, benzene ring hydrogenation occurs, leading to a mixture of aromatics and saturated hydrocarbons .…”

Section: The Challengesmentioning

confidence: 99%

Catalytic Scissoring of Lignin into Aryl Monomers

Wang

2019

Advanced Materials

133

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Lignin is an aromatic polymer, which is the biggest and most sustainable reservoir for aromatics. The selective conversion of lignin polymers into aryl monomers is a promising route to provide aromatics, but it is also a challenging task. Compared to cellulose, lignin remains the most poorly utilized biopolymer due to its complex structure. Although harsh conditions can degrade lignin, the aromatic rings are usually destroyed. This article comprehensively analyzes the challenges facing the scissoring of lignin into aryl monomers and summarizes the recent progress, focusing on the strategies and the catalysts to address the problems. Finally, emphasis is given to the outlook and future directions of this research.

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Section: The Challengesmentioning

confidence: 99%

Catalytic Scissoring of Lignin into Aryl Monomers

Wang

2019

Advanced Materials

133

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“…[7] In addition, much research has been carried out to transform lignin model compounds into chemicals or fuels. [8] Although satisfactory results have been achieved with different model compounds, the catalytic systems are usually not efficient for the conversion of real lignin. Moreover,i ti sagreat challenge to produce ac hemical with high selectivity because of the complex structure of lignin.…”

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confidence: 99%

Selective Utilization of the Methoxy Group in Lignin to Produce Acetic Acid

et al. 2017

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Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (-OCH ) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by-product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.

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“…[1a,2] In arecent breakthrough, Hartwig and Sergeev used homogeneous nickel complexes [5a] in the presence of NaOtBu base to catalyze the selective cleavage of aryl C À O bonds under relatively mild conditions in m-xylene as the solvent without hydrogenating the arene rings and cleaving aliphatic CÀOb onds.T he reaction could also be accomplished using Ni nanoparticles. [9] Supported Ni or NiM (M = Ru, Rh, Au,o rP d) bimetallic catalysts can catalyze this cleavage at significantly higher rates in water, but always lead also to some ring saturation. [5b,10] Hydrolysis of aromatic CÀOb onds is known to be challenging,r equiring harsh conditions such as using water near or above its supercritical point or strong acids/bases at high temperatures.…”

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confidence: 99%

Palladium‐Catalyzed Hydrolytic Cleavage of Aromatic C−O Bonds

et al. 2017

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Metallic palladium surfaces are highly selective in promoting the reductive hydrolysis of aromatic ethers in aqueous phase at relatively mild temperatures and pressures of H 2 .Atquantitative conversions,the selectivity to hydrolysis products of PhOR ethers was observed to range from 50 % (R = Ph) to greater than 90 %( R= n-C 4 H 9 ,c yclohexyl, and PhCH 2 CH 2 ). By analysis of the evolution of products with and without incorporation of H 2 18 O, the pathway was concluded to be initiated by palladium metal catalyzedp artial hydrogenation of the phenyl group to an enol ether.W ater then rapidly adds to the enol ether to form ah emiacetal, which then undergoes elimination to cyclohexanone and phenol/alkanol products.Ar emarkable feature of the reaction is that the stronger PhÀObond is cleaved rather than the weaker aliphatic O À Rb ond.

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Chemo‐ and Regioselective Hydrogenolysis of Diaryl Ether C−O Bonds by a Robust Heterogeneous Ni/C Catalyst: Applications to the Cleavage of Complex Lignin‐Related Fragments

Cited by 138 publications

References 61 publications

Catalytic Scissoring of Lignin into Aryl Monomers

Catalytic Scissoring of Lignin into Aryl Monomers

Selective Utilization of the Methoxy Group in Lignin to Produce Acetic Acid

Palladium‐Catalyzed Hydrolytic Cleavage of Aromatic C−O Bonds

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