Fragmentation of structural units of lignin promoted by persulfate through selective C–C cleavage under mild conditions

Luo, Fei‐Xian; Zhou, Taigang; Li, Xin; Luo, Yun-Lei; Shi, Zhang‐Jie

doi:10.1039/c5qo00116a

“…However, the lower yield of the desired phenolic compounds was afforded (10–30 % yield), possibly due to over‐oxidization and/or the formation of low polymer. This observed result is in accordance with previous reports on the oxidative cleavage of lignin model compounds …”

Section: Resultssupporting

confidence: 94%

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

Luo

¹

,

Wang

²

,

Shang

³

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.

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“…The β‐1 linkage resembles the β‐O‐4 linkage but without the CO bond. Only a few works have investigated the cleavage of β‐1 linkages . The catalytic systems for the C α C β bond cleavage of the β‐O‐4 linkage are generally effective toward the β‐1 linkage .…”

Section: The Challengesmentioning

confidence: 99%

Catalytic Scissoring of Lignin into Aryl Monomers

Wang

¹

,

Wang

²

2019

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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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“…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

Luo

¹

,

Wang

²

,

Shang

³

et al. 2020

View full text Add to dashboard Cite

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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Fragmentation of structural units of lignin promoted by persulfate through selective C–C cleavage under mild conditions

Abstract: A high selectivity and activity for the fragmentation of β-O-4 and β-1 lignin models to high-value chemicals were achieved by using persulfate.

Cited by 22 publications

References 57 publications

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

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

Catalytic Scissoring of Lignin into Aryl Monomers

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

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