10548-77-3Relevant articles and documents
Role of laccase as an enzymatic pretreatment method to improve lignocellulosic saccharification
Heap, Lucy,Green, Anthony,Brown, David,Van Dongen, Bart,Turner, Nicholas
, p. 2251 - 2259 (2014)
The recalcitrant nature of lignocellulose, in particular due to the presence of lignin, is found to decrease the efficiency of cellulases during the saccharification of biomass. The efficient and cost effective removal of lignin is currently a critical bi
Cleavage of CC and Co bonds in β-O-4 linkage of lignin model compound by cyclopentadienone group 8 and 9 metal complexes
Kishino, Masamichi,Kusumoto, Shuhei,Nozaki, Kyoko
, p. 477 - 480 (2020)
Degradation of 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphe-noxy)propane-1,3-diol (1), a model compound for lignin β-O-4 linkage was examined with iron, ruthenium, rhodium and iridium complexes bearing cyclopentadienone ligand. Cyclopentadienone iron complex gave only a small amount of degraded product with reduced molecular weight. Cyclopentadienone ruthenium complex, so called Shvo's catalyst, afforded 3,4-dimethoxybenzaldehyde (a3) in 14.3% yield after CαCβ bond cleavage. On the other hand, cyclopentadienone group-9 metal complexes catalyzed CβO bond cleavage to afford guaiacol (b1) as a main product in up to 74.9% yield.
Hydrogenolysis of a γ-Acetylated Lignin Model Compound with a Ruthenium-Xantphos Catalyst
Wu, Adam,Lauzon, Jean Michel,James, Brian R.
, p. 511 - 518 (2015)
Catalytic hydrogenolysis of a γ-acetylated dimer lignin model compound is effected using a Ru-xantphos catalyst. Mechanistic investigations show mono-aryl degradation products are generated from the β-O-4 substrate as well as a terminal alkene ketone dimer (bis-aryl) that further dimerizes to a tetra-aryl product. Preliminary results using an acetylated kraft lignin as a substrate are also discussed. Graphical Abstract: [Figure not available: see fulltext.]
A mechanistic survey of the oxidation of alcohols and ethers with the enzyme laccase and its mediation by TEMPO
D'Acunzo, Francesca,Baiocco, Paola,Fabbrini, Maura,Galli, Carlo,Gentili, Patrizia
, p. 4195 - 4201 (2002)
The oxidation of alcohols and ethers by O2 with the enzyme laccase, mediated by the stable N-oxyl radical TEMPO, affords carbonylic products. An ionic mechanism is proposed, where a nucleophilic attack of the oxygen lone-pair of the alcohol (or ether) onto the oxoammonium form of TEMPO (generated by laccase on oxidation) takes place leading to a transient adduct. Subsequent deprotonation of this adduct a to the C-O bond leads to the carbonylic product. Additional mechanistic considerations for the laccase-mediated oxidation of ethers and thioethers are offered. The proposed mechanism is supported by: (i) investigating the inter- and intramolecular selectivity of oxidation with appropriate substrates, (ii) thermochemical considerations, and (iii) attempting a Hammett correlation for the oxidation of a series of 4-X-substituted benzyl alcohols, wherein a shift of the rate-determining step as a function of the 4-X-substituent results. Based on the above points, the lack of mediation efficiency of another stable N-oxyl radical (viz., IND-O) can be explained. Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2002.
Iron-catalysed oxidative cleavage of lignin and β-O-4 lignin model compounds with peroxides in DMSO
Mottweiler, Jakob,Rinesch, Torsten,Besson, Claire,Buendia, Julien,Bolm, Carsten
, p. 5001 - 5008 (2015)
Simple FeCl3-derived iron catalysts are used for the cleavage of β-O-4 linkages in lignin and lignin model compounds. The degradation of the β-O-4 linkages and the resinol structures in both organosolv and kraft lignin was proven by 2D-NMR (HSQC) experiments, and the oxidative depolymerisation of these lignin sources was confirmed by GPC. Key reactive species facilitating this cleavage are methyl radicals generated from H2O2 and DMSO.
Oxidation of non-phenolic substrates with the laccase/N-hydroxyacetanilide system: Structure of the key intermediate from the mediator and mechanistic insight
Cantarella, Gaetano,Galli, Carlo,Gentili, Patrizia
, p. 366 - 372 (2004)
We have investigated the reactivity and mechanistic features in the oxidation of non-phenolic substrates by the enzyme laccase under mediation by N-hydroxyacetanilide, NHA. A radical route of hydrogen-abstraction by the 2 bonds on the righthand side signN
One-Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles
Guo, Tao,He, Jianghua,Liu, Tianwei,Zhang, Yuetao
, (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.
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.
