14385-49-0Relevant academic research and scientific papers
Cleavage∕cross-coupling strategy for converting β-O-4 linkage lignin model compounds into high valued benzyl amines via dual C–O bond cleavage
Jia, Le,Li, Chao-Jun,Zeng, Huiying
, (2021/10/29)
Lignin is the most recalcitrant of the three components of lignocellulosic biomass. The strength and stability of the linkages have long been a great challenge for the degradation and valorization of lignin biomass to obtain bio-fuels and commercial chemicals. Up to now, the selective cleavage of C–O linkages of lignin to afford chemicals contains only C, H and O atoms. Our group has developed a cleavage/cross-coupling strategy for converting 4-O-5 linkage lignin model compounds into high value-added compounds. Herein, we present a palladium-catalyzed cleavage/cross-coupling of the β-O-4 lignin model compounds with amines via dual C–O bond cleavage for the preparation of benzyl amine compounds and phenols.
1,3-Dibromo-5,5-dimethylhydantoin (DBH)/DMSO mediated oxidative difunctionalization of styrenes: Microfluidic synthesis of pentafluorophenoxy ketone
Xu, Jia,Hua, Jiawei,Bian, Mixue,Li, Yuguang,He, Wei,Yang, Zhao,Liu, Chengkou,Fang, Zheng,Guo, Kai
, (2021/02/27)
A practical and mild synthesis of pentafluorophenoxy ketone in a continuous flow microfluidic reactor has been developed through 1,3-Dibromo-5,5-dimethylhydantoin (DBH)/DMSO mediated oxidative coupling of styrenes with pentafluorophenol. Moreover, a series of pentafluorophenoxy ketone products were provided in moderate to good yields under metal-free conditions. A magnifying continuous flow system was erected to verify the appliance of this method.
Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
, p. 4037 - 4050 (2020/03/10)
We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
Sulfuryl Fluoride Mediated Synthesis of Amides and Amidines from Ketoximes via Beckmann Rearrangement
Gurjar, Jitendra,Fokin, Valery V.
, p. 10402 - 10405 (2020/07/25)
A metal-free and redox-neutral method for Beckmann rearrangement employing inexpensive and readily available SO2F2 gas is described. The reported transformation proceeds at ambient temperature and is compatible with a wide range of sterically and electronically diverse aromatic, heteroaromatic, aliphatic and lignin-like oximes providing amides in good to excellent yields. The reaction proceeds through the formation of an imidoyl fluoride intermediate that can also be used for the synthesis of amidines.
Metal-Free Twofold Electrochemical C?H Amination of Activated Arenes: Application to Medicinally Relevant Precursor Synthesis
D?rr, Carolin,Diehl, Erika,Hellmich, Ute A.,Schollmeyer, Dieter,Shimizu, Akihiro,Waldvogel, Siegfried R.,Wesenberg, Lars J.,Yoshida, Jun-ichi,Z?hringer, Till J. B.
supporting information, p. 17574 - 17580 (2020/12/07)
The efficient production of many medicinally or synthetically important starting materials suffers from wasteful or toxic precursors for the synthesis. In particular, the aromatic non-protected primary amine function represents a versatile synthetic precu
Visible-light-induced C-C bond cleavage of lignin model compounds with cyanobenziodoxolone
Zheng, Ming,Huang, Yan,Zhan, Le-Wu,Hou, Jing,Li, Bin-Dong
, (2020/10/02)
The catalytic degradation of lignin to value-added chemicals has received considerable attention over the past decade. Photocatalysis provides promising approaches to enable previously inaccessible transformations. However, examples of the visible-light promoted degradation of lignin are still limited. In this work, the visible-light-induced selective C-C bond cleavage of β-O-4 lignin model compounds has been disclosed via β-scission of in situ generated alkoxy radical intermediates. With cyanobenziodoxolone as the oxidant, a variety of substrates could be transformed into aldehydes in moderate to good yields. In addition, unexpected acetal esters which could conveniently furnish formaldehyde and phenols by alcoholysis were observed.
Activating molecular oxygen with Au/CeO2 for the conversion of lignin model compounds and organosolv lignin
Song, Wu-Lin,Dong, Qingmeng,Hong, Liang,Tian, Zhou-Qi,Tang, Li-Na,Hao, Wenli,Zhang, Hongxi
, p. 31070 - 31077 (2019/10/28)
Au/CeO2 was demonstrated to be a high efficiency catalyst for the conversion of 2-phenoxyacetophenol (PP-ol) employing O2 as an oxidant and methyl alcohol as the solvent without using an erosive strong base or acid. Mechanistic investigations, including emission quenching experiments, electron spin-resonance (ESR) and intermediate verification experiments, were carried out. The results verified that the superoxide anion activated by Au/CeO2 from molecular oxygen plays a vital role in the oxidation of lignin model compounds, and the cleavage of both the β-O-4 and Cα-Cβ linkages was involved. Au/CeO2 also performed well in the oxidative conversion of organosolv lignin under mild conditions (453 K), producing vanillin (10.5 wt%), methyl vanillate (6.8 wt%), methylene syringate (3.4 wt%) and a ring-opened product. Based on the detailed characterization data and mechanistic results, Au/CeO2 was confirmed to be a promising catalytic system.
ARYLOXYMETHYL-RADICAL FORMATION ENTHALPIES
Ponomarev, D. A.,Takhistov, V. V.,Misharev, A. D.,Orlov, V. M.
, p. 1935 - 1936 (2007/10/02)
Enthalpies of formation have been determined for six substituted phenoxymethyl radicals.Donor substituents exert a stabilizing effect on the radical center in each case, and acceptor ones have a destabilizing effect.
