104397-78-6Relevant articles and documents
Chemoselective oxidant-free dehydrogenation of alcohols in lignin using Cp?Ir catalysts
Zhu, Rui,Wang, Bing,Cui, Minshu,Deng, Jin,Li, Xinglong,Ma, Yingbo,Fu, Yao
, p. 2029 - 2036 (2016)
A remarkably effective method of chemoselective dehydrogenation of alcohols in lignin has been developed with an iridium catalyst. An additional operation of Zn/NH4Cl via a two-step one pot process could further promote the cleavage of the C-O bond in β-O-4 units in lignin. And this reaction system was also applicable to native lignin as the molecular weight of native lignin decreased obviously as detected by gel permeation chromatography (GPC). Additionally, this is the first to date generation of the by-product H2 from native lignin and the by-product was straightforwardly captured by 1-decene. A probable mechanistic pathway was also proposed with the help of density functional theory (DFT) calculations.
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%.
Organocatalytic Approach to Photochemical Lignin Fragmentation
Yang, Cheng,K?rk?s, Markus D.,Magallanes, Gabriel,Chan, Kimberly,Stephenson, Corey R. J.
, 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.
Visible light-enabled selective depolymerization of oxidized lignin by an organic photocatalyst
Hao, Zhongkai,Jiang, Huating,Li, Shuyuan,Tong, Min,Wang, Kaixuan,Xiao, Yao,Yang, Yanan,Zhang, Fang
supporting information, p. 11243 - 11246 (2020/10/06)
The development of an economic, environmental-friendly and energy-saving process for the selective depolymerization of lignin is an outstanding challenge. Herein, a novel and efficient visible-light-induced photocatalytic process for the selective depolymerization of lignin model compounds and organosolv lignin was first developed by using perylene diimide (PDI) as a metal-free organocatalyst. Interestingly, it can completely decompose the oxidized lignin models to phenolic and ketone fragmentation molecules with very high selectivity at room temperature under visible light illumination. Furthermore, the use of a home-made photocatalytic continuous-flow reactor efficiently shortened the reaction time within an hour. Even for organosolv lignin, nearly 86% mass ratio of lignin was degraded to low-molecular-mass monoaromatic or diaromatic products. We found that superior performances were realized by single-electron transfer (SET) from the photoexcited strongly reducing PDI˙?anion to the ketone groups of the β-O-4 linkage in the lignin.
Enhancing Photocatalytic β-O-4 Bond Cleavage in Lignin Model Compounds by Silver-Exchanged Cadmium Sulfide
Cha, Hyun Gil,Cho, Soyoung,Kim, Hyun Sung,Lee, Hangil,Lee, Jehee,Lee, Min-Woo,Lee, Sunggyu,Yoo, Hyeonji
, p. 8465 - 8475 (2020/09/18)
Photocatalytic conversion of lignocellulose to valuable aromatics has significant potential for applications in biorefineries. The photocatalyst efficiency of lignocellulose conversion is typically limited by the buffering redox system in combination with oxidation and reduction of the photoexcited holes and electrons, respectively, which ensures high charge-recombination rates. Herein, Ag+-exchanged CdS is employed for easy photoexcited electron transfer to the oxidized intermediate, which results in a marked increase in the conversion yield with high product selectivity under mild reaction conditions without any additives. The conversion yield of the lignin model compound under 6 W blue LED illumination is nearly 100% and only cleaved aromatic compounds are formed. The efficient photoredox CdS catalyst obtained via photoexcited electron-hole coupled transfer derived from an appropriate Ag+ exchange affords a promising method for lignocellulose conversion with reduced energy consumption.
Visible-Light-Driven Cleavage of C?O Linkage for Lignin Valorization to Functionalized Aromatics
Lin, Jinchi,Wu, Xuejiao,Xie, Shunji,Chen, Liangyi,Zhang, Qinghong,Deng, Weiping,Wang, Ye
, p. 5023 - 5031 (2019/12/02)
Lignin is the most abundant source of renewable aromatics. Catalytic valorization of lignin into functionalized aromatics is attractive but challenging. Photocatalysis is a promising sustainable approach. The strategies for designing well-performing photocatalysts are desired but remain limited. Herein, a facile energy band engineering strategy for promoting the photocatalytic activity of zinc–indium–sulfide (ZnmIn2Sm+3) for cleavage of the lignol β-O-4 bond under mild conditions was developed. The energy band structure of ZnmIn2Sm+3 could be tuned by controlling the atomic ratio of Zn/In. It was found that Zn4In2S7 performed best for cleavage of the β-O-4 bond under visible-light irradiation, owing to its appropriate energy band structure for offering adequate visible-light absorption and suitable redox capability. Functionalized aromatic monomers with near 18.4 wt % yield could be obtained from organosolv birch lignin. Mechanistic studies revealed that the β-O-4 bond was efficiently cleaved mainly through a one-step redox-neutral pathway via a Cα radical intermediate. The thiol groups on the surface of Zn4In2S7 played a key role in cleavage of the β-O-4 bond.
Fine Tuning the Redox Potentials of Carbazolic Porous Organic Frameworks for Visible-Light Photoredox Catalytic Degradation of Lignin β-O-4 Models
Luo, Jian,Zhang, Xiang,Lu, Jingzhi,Zhang, Jian
, p. 5062 - 5070 (2017/08/17)
We report a facile approach to fine tune the redox potentials of π-conjugated porous organic frameworks (POFs) by copolymerizing carbazolic electron donor (D) and electron acceptor (A) based comonomers at different ratios. The resulting carbazolic copolymers (CzCPs) exhibit a wide range of redox potentials that are comparable to common transition-metal complexes and are used in the stepwise photocatalytic degradation of lignin β-O-4 models. With the strongest oxidative capability, CzCP100 (D:A = 0:100) exhibits the highest efficiency for the oxidation of benzylic β-O-4 alcohols, while the highly reductive CzCP33 (D:A = 66:33) gives the highest yield for the reductive cleavage of β-O-4 ketones. CzCPs also exhibit excellent stability and recyclability and represent a class of promising heterogeneous photocatalysts for the production of fine chemicals from sustainable lignocellulosic biomass.
Visible light mediated reductions of ethers, amines and sulfides
Monos, Timothy M.,Magallanes, Gabriel,Sebren, Leanne J.,Stephenson, Corey R.J.
, p. 240 - 248 (2016/07/21)
Visible light-mediated photoredox catalysis enables the chemoselective reduction of activated carbon–heteroatom bonds as a function of reduction potential. The expansion of the scope of C–X bond reductions towards less activated motifs, such as ethers, amines and sulfides, is important to both organic synthesis and macromolecular degradation method development. In the present report, exploration of photoredox catalysis in alcoholic solvents mediated a decrease in the super-stoichiometric use of iPr2NEt and HCO2H in the reduction of α-keto ethers, amines and sulfides. Additionally, in the absence of fragmentation, [Formula presented] bond formation was afforded, suggesting an intermediate ketyl radicals are present in these transformations.
Isolation of functionalized phenolic monomers through selective oxidation and CO bond cleavage of the β-O-4 linkages in Lignin
Lancefield, Christopher S.,Ojo, O. Stephen,Tran, Fanny,Westwood, Nicholas J.
supporting information, p. 258 - 262 (2015/02/19)
Functionalized phenolic monomers have been generated and isolated from an organosolv lignin through a two-step depolymerization process. Chemoselective catalytic oxidation of β-O-4 linkages promoted by the DDQ/tBuONO/ O2 system was achieved in model compounds, including polymeric models and in real lignin. The oxidized β-O-4 linkages were then cleaved on reaction with zinc. Compared to many existing methods, this protocol, which can be achieved in one pot, is highly selective, giving rise to a simple mixture of products that can be readily purified to give pure compounds. The functionality present in these products makes them potentially valuable building blocks.
A photochemical strategy for lignin degradation at room temperature
Nguyen, John D.,Matsuura, Bryan S.,Stephenson, Corey R. J.
supporting information, p. 1218 - 1221 (2014/02/14)
The development of a room-temperature lignin degradation strategy consisting of a chemoselective benzylic oxidation with a recyclable oxidant ([4-AcNH-TEMPO]BF4) and a catalytic reductive C-O bond cleavage utilizing the photocatalyst [Ir(ppy)2(dtbbpy)]PF6 is described. This system was tested on relevant lignin model substrates containing β-O-4 linkages to generate fragmentation products in good to excellent yields.
