Covalent triazine framework catalytic oxidative cleavage of lignin models and organosolv lignin

Zhao, Li; Shi, Song; Liu, Meng; Zhu, Guozhi; Wang, Min; Du, Wentao; Gao, Jin; Xu, Jie

doi:10.1039/c8gc00268a

Cited by 63 publications

(49 citation statements)

References 67 publications

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“…8). Firstly, with the assistance of K 2 CO 3 , 1-phenylethane-1,2-diol (1a) was oxidized to the 2-hydroxy-1-phenylethanone (5a) (or the tautomer 5b as well) by the active species generated from the activation of oxygen by the Co-based catalyst [36][37][38][39][40] . Then, there are two possible reaction pathways for this reaction.…”

Section: Resultsmentioning

confidence: 99%

Aerobic oxidative cleavage of 1,2-diols catalyzed by atomic-scale cobalt-based heterogeneous catalyst

et al. 2019

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The oxidative cleavage of the CC bonds in 1,2-diols is an important transformation in synthetic organic chemistry. The challenge for this reaction is to develop a recyclable catalyst and an efficient catalytic system that operates under mild conditions. Here we report an atomically dispersed cobalt (3.8 wt% Co) on N-doped carbon catalyst, which exhibits improved catalytic activity toward the oxidative cleavage of a variety of 1,2-diols into esters, ketones or aldehydes using molecular oxygen under mild conditions. For example, the oxidative cleavage of internal diols is achieved at ambient temperature and air pressure. The robust catalyst can be reused at least seven times without regeneration treatment. The formation of highly dispersed active CoN x sites is demonstrated by catalyst characterization and potassium thiocyanate poisoning experiment. Mechanistic insights into monosubstituted diols indicate a sequence reaction including stepwise oxidation/nucleophilic addition/C-C bond cleavage, and reveal two reaction pathways.

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Section: Resultsmentioning

confidence: 99%

Aerobic oxidative cleavage of 1,2-diols catalyzed by atomic-scale cobalt-based heterogeneous catalyst

et al. 2019

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“…Thec orresponding aromatic esters were obtained in good to moderate yields.Specifically,the catalytic system can also effectively oxidize cleavage of complex lignin models with Cg-OH into corresponding esters in moderate yields.H owever,t he lower yield of the desired phenolic compounds was afforded (10-30 %y ield), possibly due to over-oxidization and/or the formation of low polymer.T his observed result is in accordance with previous reports on the oxidative cleavage of lignin model compounds. [18][19][20][21][22][23] To better elucidate the mechanism of the oxidative cleavage of secondary alcohols to esters,wefirst implemented ar adical inhibition experiments to determine whether the reaction involves free radicals.T he results showed that the radical scavengers 2,6-di-tertbutyl-4-methylphenol (BHT) or (2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) had no effect on the formation of target products (Supporting Information, Scheme S1), thus suggesting that the radical reaction process can be ruled out.…”

Section: Angewandte Chemiementioning

confidence: 99%

Cobalt Nanoparticles‐Catalyzed Widely Applicable Successive C−C Bond Cleavage in Alcohols to Access Esters

et al. 2020

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Selective cleavage and functionalization of C À C bonds have important applications in organic synthesis and biomass utilization. However,functionalization of CÀCbonds by controlled cleavage remains difficult and challenging because they are inert. Herein, we describe an unprecedented efficient protocol for the breaking of successive C À Cbonds in alcohols to form esters with one or multiple carbon atoms less using heterogeneous cobalt nanoparticles as catalyst with dioxygen as the oxidant. Aw ide range of alcohols including inactive long-chain alkyl aryl alcohols undergo smoothly successive cleavage of adjacent À(CÀC) n À bonds to affordt he corresponding esters.T he catalyst was used for seven times without any decrease in activity.C haracterization and control experiments disclose that cobalt nanoparticles are responsible for the successive cleavage of C À Cb onds to achievee xcellent catalytic activity,w hile the presence of CoN x has just the opposite effect. Preliminary mechanistic studies reveal that atandem sequence reaction is involved in this process. Scheme 1. Successive CÀCbond cleavage of alcohols.

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“…They can be reductive or employ redox-neutral catalysis, 8 acid- or base-catalysis, 9 and oxidative catalysis. 10 For oxidative transformations, it was found that α-oxidation of the secondary alcohol group in the β-O-4 motif in lignin or in similar lignin model compounds decreased the bond strength of the neighboring C–C and C–O bonds. 11 Stephenson and co-workers validated this observation by density functional theory calculations with respect to the cleavage of adjacent C–O bond in β-O-4 model systems (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Cobalt-Catalyzed Oxidation of the β-O-4 Bond in Lignin and Lignin Model Compounds

Rinesch

Bolm

2018

ACS Omega

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In this work we demonstrate the use of Co(acac) 3 in combination with N -hydroxyphthalimide as an oxidant for the selective α-oxidation of the representative β-O-4 linkages in lignin model compounds. The oxidation reaction proceeds under mild conditions at 80 °C using 1,4-dioxane as the solvent and an oxygen atmosphere. The prior α-oxidation in the β-O-4 linkage of the lignin polymer is known to result in an easier cleavage of the adjacent C–O and C–C bonds because of a decrease in bond stability. Finally, the conditions were successfully transferred to kraft- and organosolv-lignin samples as proven by 2D-NMR (HSQC) experiments and gel permeation chromatography measurements.

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Covalent triazine framework catalytic oxidative cleavage of lignin models and organosolv lignin

Abstract: CTFs were used as effective metal-free catalysts for the oxidative cleavage of lignin model compounds and organosolv lignin.

Cited by 63 publications

References 67 publications

Aerobic oxidative cleavage of 1,2-diols catalyzed by atomic-scale cobalt-based heterogeneous catalyst

Aerobic oxidative cleavage of 1,2-diols catalyzed by atomic-scale cobalt-based heterogeneous catalyst

Cobalt Nanoparticles‐Catalyzed Widely Applicable Successive C−C Bond Cleavage in Alcohols to Access Esters

Cobalt-Catalyzed Oxidation of the β-O-4 Bond in Lignin and Lignin Model Compounds

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