91-10-1Relevant articles and documents
One-Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles
Guo, Tao,He, Jianghua,Liu, Tianwei,Zhang, Yuetao
supporting information, (2022/02/07)
It is a challenging task to simultaneously achieve selective depolymerization and valorization of lignin due to their complex structure and relatively stable bonds. We herein report an efficient depolymerization strategy that employs 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as oxidant/catalyst to selectively convert different oxidized lignin models to a wide variety of 2-phenylbenzimidazole-based compounds in up to 94 % yields, by reacting with o-phenylenediamines with varied substituents. This method could take full advantage of both Cβ and/or Cγ atom in lignin structure to furnish the desirable products instead of forming byproducts, thus exhibiting high atom economy. Furthermore, this strategy can effectively transform both the oxidized hardwood (birch) and softwood (pine) lignin into the corresponding degradation products in up to 45 wt% and 30 wt%, respectively. Through a “one-pot” process, we have successfully realized the oxidation/depolymerization/valorization of natural birch lignin at the same time and produced the benzimidazole derivatives in up to 67 wt% total yields.
Thio-assisted reductive electrolytic cleavage of lignin β-O-4 models and authentic lignin
Fang, Zhen,Flynn, Michael G.,Jackson, James E.,Hegg, Eric L.
supporting information, p. 412 - 421 (2021/01/28)
Avoiding the use of expensive catalysts and harsh conditions such as elevated temperatures and high pressures is a critical goal in lignin depolymerization and valorization. In this study, we present a thio-assisted electrocatalytic reductive approach using inexpensive reticulated vitreous carbon (RVC) as the working cathode to cleave the β-O-4-type linkages in keto aryl ethers. In the presence of a pre-electrolyzed disulfide (2,2′-dithiodiethanol) and a radical inhibitor (BHT) at room temperature at a current density of 2.5 mA cm-2, cathodic reduction of nonphenolic β-O-4 dimers afforded over 90% of the corresponding monomeric C-O cleavage products in only 1.5 h. Extended to DDQ-oxidized poplar lignin, this combination of electric current and disulfide, applied over 6 h, released 36 wt% of ethyl acetate soluble fragments and 26 wt% of aqueous soluble fragments, leaving only 38 wt% of insoluble residue. These findings represent a significant improvement over the current alone values (24 wt% ethyl acetate soluble; 22 wt% aqueous soluble; 54 wt% insoluble residue) and represent an important next step in our efforts to develop a mild electrochemical method for reductive lignin deconstruction.
Application of tungsten oxide supported monatomic catalyst in preparation of aromatic compound by hydrogenolysis of lignin
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Paragraph 0044-0051, (2021/05/22)
The invention provides application of a tungsten oxide supported monatomic catalyst in preparation of aromatic compounds by hydrogenolysis of lignin. According to the method, various beta-O-4 model molecules, organic lignin, lignosulfonate and alkali lignin are taken as raw materials, and high-selectivity cracking of aryl ether bonds is realized in a hydrogen atmosphere at the temperature of 150-240 DEG C and the pressure of 0.7-3.0 MPa to obtain the aromatic compound. Compared with the prior art, the method has the advantages that when renewable natural biomass is used as the raw material and different lignin is used as the raw material for conversion, the highest yield of the aromatic bio-oil is 72%. Raw materials are cheap and wide in source; inorganic acid and alkali are not needed, and generation of a large amount of alkali liquor in traditional lignin catalysis is avoided; the method has the characteristics of cheap tungsten-based catalyst, green reaction process, atom economy and the like, and also has the characteristics of mild reaction conditions, high activity and selectivity, environment-friendly reaction process and the like.
Electro-reductive Fragmentation of Oxidized Lignin Models
Yang, Cheng,Magallanes, Gabriel,Maldonado, Stephen,Stephenson, Corey R. J.
, p. 15927 - 15934 (2021/06/30)
Lignin provides a potential sustainable source for production of electron-rich aromatic compounds. Recently, electrochemical lignin degradation via an oxidation/reduction sequence under mild conditions has garnered much attention within the lignin community, as electrochemistry simplifies redox reactions and offers an electron source/sink for synthesis without using stoichiometric oxidants or reductants. This paper describes a fundamental approach for the electrochemical fragmentation of the primary connection in native lignin, β-O-4. Potential-controlled electrolysis enables selective reduction and provides fragmentation products and/or coupling products in isolated yields of 59-92%.
Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
, p. 3090 - 3103 (2021/05/07)
Lignin is an abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-value chemicals. Selective hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CS catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Yderived catalysts were produced using different compositions at different temperatures (X= 0 mg, 0.2 mg, 0.4 mg, 0.6 mg, and 0.8 mg; Y = 600 °C, 700 °C, 800 °C, and 900 °C) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of the obtained corresponding ethylbenzene and phenol could achieve 92% and 86%, respectively, over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 °C without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage of the lignin ether bonds. The physicochemical characterization studies were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Raman and XPS analyses. Based on the optimal reaction conditions (260 °C, 4 h, 2.0 MPa N2), various model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce the corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in the next five consecutive cycle experiments with a slight decrease in the transformation of lignin model compounds.
The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
, p. 18040 - 18049 (2021/05/29)
An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
Catalytic C(β)-O Bond Cleavage of Lignin in a One-Step Reaction Enabled by a Spin-Center Shift
Zhu, Qilei,Nocera, Daniel G.
, p. 14181 - 14187 (2021/11/27)
A challenge to the utilization of lignin as a feedstock for aromatic fine chemicals lies in selective cleavage of copious β-O-4 linkages. A photocatalytic strategy for the selective cleavage of the C(β)-O bonds of model substrates and natural lignin extracts is achieved by a redox-neutral, catalytic cycle that does not require stoichiometric reagents. Mechanistic studies reveal the generation of a thiyl radical, which is derived from a cystine-derived H-atom transfer catalyst, initiates a spin-center shift (SCS) that leads to C(β)-O bond cleavage. The SCS reactivity is reminiscent of the C(β)-O bond cleavage chemistry that occurs in the active site of ribonucleotide reductase.
Sustainable Production of Benzylamines from Lignin
Guo, Tenglong,Kühn, Fritz E.,Li, Changzhi,Liu, Yuxuan,Wang, Chao,Xiao, Jianliang,Zhang, Bo,Zhang, Tao,Zhao, Zongbao K.
supporting information, p. 20666 - 20671 (2021/08/25)
Catalytic conversion of lignin into heteroatom functionalized chemicals is of great importance to bring the biorefinery concept into reality. Herein, a new strategy was designed for direct transformation of lignin β-O-4 model compounds into benzylamines and phenols in moderate to excellent yields in the presence of organic amines. The transformation involves dehydrogenation of Cα?OH, hydrogenolysis of the Cβ?O bond and reductive amination in the presence of Pd/C catalyst. Experimental data suggest that the dehydrogenation reaction proceeds over the other two reactions and secondary amines serve as both reducing agents and amine sources in the transformation. Moreover, the concept of “lignin to benzylamines” was demonstrated by a two-step process. This work represents a first example of synthesis of benzylamines from lignin, thus providing a new opportunity for the sustainable synthesis of benzylamines from renewable biomass, and expanding the products pool of biomass conversion to meet future biorefinery demands.
Organocatalytic Approach to Photochemical Lignin Fragmentation
Yang, Cheng,K?rk?s, Markus D.,Magallanes, Gabriel,Chan, Kimberly,Stephenson, Corey R. J.
supporting information, p. 8082 - 8085 (2020/11/02)
Herein, an organocatalytic method for photochemical C-O bond cleavage of lignin systems is reported. The use of photochemistry enabled fragmentation of the β-O-4 linkage, the primary linkage in lignin, provides the fragmentation products in good to high yields. The approach was merged with reported oxidation conditions in a one-pot, two-step platform without any intermediary purification, suggesting its high fidelity. The future utility of the organocatalytic method was illustrated by applying the visible light-mediated protocol to continuous flow processing.
Mechanochemical cleavage of lignin models and ligninviaoxidation and a subsequent base-catalyzed strategy
Dushkin, Alexandr V.,Su, Weike,Sun, Chen,Xu, Wenhao,Zheng, Lei
supporting information, p. 3489 - 3494 (2020/07/30)
Mechanochemical cleavage of lignin dimer model compounds to phenolic monomers has been developedviaa two-step strategy under milling conditions. In the first step of this process, the secondary benzylic alcohol of lignin β-O-4 linkages was selectively oxidized to the corresponding ketones over a 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/NaNO2catalytic system under milling conditions. In the subsequent step, mechanochemical selective cleavage of the Cβ-O bonds and Cα-Cβbonds of lignin β-O-4 ketones to acids and phenols was promoted by NaOH-catalyzed depolymerization. In addition, this two-step strategy was performed to depolymerize organosolv birch lignin, giving aromatic monomers with good selectivity for syringate. This approach provides an efficient method to convert the β-O-4 linkages of lignin to valuable aromatic monomers under mild reaction conditions.
