cas 40515-89-7, 2-PHENYLETHYL PHENYL ETHER

Articles about 40515-89-7Total 38 be found

Article title
Article abstract
Author
Journal number and time
Download

Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
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.
Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
p. 3090 - 3103
(2021/05/07)

Environmentally-friendly and sustainable synthesis of bimetallic NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers
This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were synthesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The structures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH3-TPD. The synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions. In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor catalyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a catalytic transfer hydrogenation process and led to very high product yields.
Chen, Changzhou,Jiang, Jianchun,Liu, Peng,Ren, Jurong,Wu, Dichao,Xia, Haihong,Zhou, Minghao
(2021/08/05)

Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
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.
Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
supporting information
p. 4037 - 4050
(2020/03/10)

Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
p. 3802 - 3808
(2020/07/09)

Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
supporting information
p. 5556 - 5564
(2019/10/28)

Catalytic cleavage of the Β-O-4 aryl ether bonds of lignin model compounds by Ru/C catalyst
Lignin is a potential renewable feedstock for aromatic compounds. Lignin glues cellulose and hemicellulose together in a rigid structure that protects plants from weather, insects, and disease. This rigidity also poses a barrier to cleavage of lignin into
Hossain, Md Anwar,Phung, Thanh Khoa,Rahaman, Mohammad Shahinur,Tulaphol, Sarttrawut,Jasinski, Jacek B.,Sathitsuksanoh, Noppadon
(2019/06/27)

Selective Cleavage of C?O Bonds in Lignin Catalyzed by Rhenium(VII) Oxide (Re2O7)
The selective cleavage of C?O bonds in typical model lignin β-O-4 compounds and deconstruction of a realistic lignin feedstock catalyzed by Re2O7 is described. High yields of C?O cleavage products (up to 97.8 %) from model compounds and oils (76.3 %) from organosolv pinewood lignin were obtained under mild conditions. Evidence for the pathway of this catalytic process is also provided.
Qi, Zaojuan,Zhang, Bo,Ji, Jianwei,Li, Xinxin,Dai, Tao,Guo, Haiwei,Wang, Aiqin,Lu, Lican,Li, Changzhi
p. 500 - 505
(2018/03/27)

Selective reductive cleavage of C–O bond in lignin model compounds over nitrogen-doped carbon-supported iron catalysts
Lignin has recently attracted much attention as a promising resource to produce fuels and aromatic chemicals. The selective cleavage of C–O bond while preserving the aromatic nature has become one of the major challenges in the catalytic valorization of lignin to aromatic chemicals. In this work, we report that the selective reductive cleavage of C–O bond in lignin model compounds can be successfully achieved through heterogeneous iron catalysis. The hydrogenolysis of α-O-4 model linkage shows that the iron catalyst prepared by the simultaneous pyrolysis of iron acetate and 1,10-phenanthroline on activated carbon at 800 °C is the most active iron catalyst, affording phenol and toluene with yields of 95% and 90%, respectively. This aromatics selectivity is found to be much higher than that obtained over noble metal catalysts. The presence of N?Fe species as the active center of heterogeneous iron catalyst was confirmed by various technologies especially XPS and H2-TPR. For the β-O-4 model linkage, the vicinal –OH group was essential for the iron-catalyzed hydrogenolysis of ether linkage. The oxidation of the α-carbon in the β-O-4 model compounds can significantly decrease the bond dissociation energy of ether linkage, giving depolymerization products in moderate to excellent yields.
Li, Jiang,Sun, Hui,Liu, Jia-xing,Zhang, Jun-jie,Li, Zhen-xing,Fu, Yao
p. 36 - 45
(2018/04/10)

Ni/HZSM-5 catalyst preparation by deposition-precipitation. Part 2. Catalytic hydrodeoxygenation reactions of lignin model compounds in organic and aqueous systems
Nickel metal supported on HZSM-5 (zeolite) is a promising catalyst for lignin depolymerization. In this work, the ability of catalysts prepared via deposition-precipitation (DP) to perform hydrodeoxygenation (HDO) on two lignin model compounds in organic and aqueous solvents was evaluated; guaiacol in dodecane and 2-phenoxy-1-phenylethanol (PPE) in aqueous solutions. All Ni/HZSM-5 catalysts were capable of guaiacol HDO into cyclohexane at 523 K. The role of the HZSM-5 acid sites was confirmed by comparison with Ni/SiO2 (inert support) which exhibited incomplete deoxygenation of guaiacol due to the inability to perform the cyclohexanol dehydration step. The catalyst prepared with 15 wt% Ni, a DP time of 16 h, and a calcination temperature of 673 K (Ni(15)/HZSM-5 DP16_Cal673), performed the guaiacol conversion with the greatest selectivity towards HDO products, with an intrinsic rate ratio (HDO rate to conversion rate) of 0.31, and 90% selectivity to cyclohexane. Catalytic activity and selectivity of Ni/HZSM-5 (15 wt%) in aqueous environments (water and 0.1 M NaOH solution) was confirmed using PPE reactions at 523 K. After 30 min reaction time in water, Ni/HZSM-5 exhibited ～100% conversion of PPE, and good yield of the desired products; ethylbenzene and phenol (～35% and 23% of initial carbon, respectively). Ni/HZSM-5 in NaOH solution resulted in significantly higher ring saturation compared to the Ni/HZSM-5 in water or the NaOH solution control.
Barton,Carrier,Segura,Fierro,Park,Lamb,Escalona,Peretti
p. 294 - 309
(2018/06/26)

Metal-Free I2-Catalyzed Highly Selective Dehydrogenative Coupling of Alcohols and Cyclohexenones
The I2 catalyzed highly selective oxidative condensation of cyclohexenones and alcohols for the synthesis of aryl alkyl ethers has been described. DMSO is employed as the mild terminal oxidant. This novel methodology offers a metal-free reaction condition, operational simplicity and broad substrate scope to afford valuable products from inexpensive reagents. Various meta-substituted aromatic ethers which are hardly synthesized from the reported methods requiring meta-substituted phenols, are efficiently prepared by the present protocol.
Liang, Yu-Feng,Yuan, Yizhi,Shen, Tao,Song, Song,Jiao, Ning
p. 233 - 240
(2018/02/19)

Buchwald-Hartwig amination reaction of aryl halides using heterogeneous catalyst based on Pd nanoparticles decorated on chitosan functionalized graphene oxide
In this work, graphene oxide was functionalized with chitosan (GO-Chit) followed by a simple approach for immobilization of palladium nanoparticles onto a chitosan grafted graphene oxide surface. The Pd-nanocomposite (GO-Chit-Pd) was characterized using Transmission Electron Microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) measurements. The catalytic activity of the prepared heterogeneous graphene oxide functionalized chitosan-palladium (GO-Chit-Pd) was investigated in term of C-N coupling reaction (Buchwald-Hartwig amination reaction of aryl halides) yielding products of N-arylamines. The easy purification, convenient operation, and environmental friendliness, combined with a high yield, render this method viable for use in both laboratory research and larger industrial scales. Studying the reusability of the catalyst in this work showed that it could be reused for five times without obvious loss in catalytic activity.
Sarvestani, Mosayeb,Azadi, Roya
(2017/10/05)

Cleavage of ethers in an ionic liquid. Enhancement, selectivity and potential application
The cleavage of a series of ethers was examined in an ionic liquid containing hydrogen bromide. Reactions that did not proceed in either water or DMSO were found to proceed readily in this system, with notable selectivity between the cleavage of the different ether types examined herein. Increasing the proportion of water in the reaction mixture dramatically decreased the rate constant of ether cleavage; this could, in part, be attributed to a decrease in the solvent stabilisation of the transition state. Through analysis of the electronic requirements of the reaction (using substrates containing substituents with different Hammett parameters) and observation of rate enhancements for an ortho substituted system, the importance of the extent of protonation of the ether prior to nucleophilic attack was demonstrated.
Hart, William E. S.,Aldous, Leigh,Harper, Jason B.
supporting information
p. 5556 - 5563
(2017/07/12)

Highly Stable and Recyclable Graphene Layers Protected Nickel–Cobalt Bimetallic Nanoparticles as Tunable Hydrotreating Catalysts for Phenylpropane Linkages in Lignin
Abstract: Nickel–cobalt bimetallic nanoparticles coated with several layers of graphene were developed through direct heating treatment of bimetallic oxide precursor prepared by the modified Pechini-type sol–gel method. These nanomaterials were demonstrated to be versatile catalysts for lignin depolymerization. The catalysts showed unexpectedly tunable selectivity that directly depends on the composition of bimetallic nanoparticles. Dimeric lignin model compounds can be converted totally and the hydrogenolysis selectivities above 85% over Ni–Co@C (Ni:Co = 1:3). During the recycling test, the nanocatalyst showed excellent recyclability in the ten-batch investigation. The deposition of graphene layers over bimetal nanoparticles fosters a subtle balance between protecting effects and surface accessibility to catalytic reactions and significantly improves their stability to air and moisture. Ni–Co@C catalysts were readily separated from the liquid mixtures with high recycling ratio due to their magnetic properties. Graphical Abstract: [Figure not available: see fulltext.] Ni–Co bimetallic nanoparticles are coated with graphene layers. Graphene layers over the nanoparticles protect them from deactivation. Ni–Co@C shows tunable selectivity in the hydrogenolysis of dimeric lignin linkage. The non-precious metal catalyst showed excellent recyclability and can be reused ten times without significant loss of activity.
Chen, Bingfeng,Li, Fengbo,Yuan, Guoqing
p. 2877 - 2885
(2017/09/18)

Investigation on the cleavage of Β-O-4 linkage in dimeric lignin model compound over nickel catalysts supported on ZnO-Al2O3 composite oxides with varying Zn/Al ratios
Catalytic depolymerization of lignin is still a challenge due to its low conversion and repolymerization of the reactive intermediates. Reductive depolymerization over supported nickel catalysts with probable surface acidic and basic properties is a very promising process. It is therefore very important to investigate the effect of acidity and basicity of the supports on catalytic reactivity. In this paper, we synthesized a series of nickel based catalysts supported on ZnO-Al2O3 composites with varying Zn/Al atom ratios (Zn/Al = 2, 3, 5, ∞) and tested their catalytic performances over a model compound 2-phenoxy-1-phenylethanone containing β-O-4 bond. All these catalysts showed 100% conversion by reacting at 250 °C for 2 h under 2 MPa of H2. Higher selectivity towards ethylcyclohexane could be obtained over the catalyst Ni/ZnO-Al2O3-5. The possible cleavage pathways of selective oxidized β-O-4 ether linkage have been proposed.
Xu, Chen,Tang, Si-Fu,Sun, Xianyong,Sun, Yuanyuan,Li, Guangci,Qi, Jingbo,Li, Xiaoyu,Li, Xuebing
p. 89 - 98
(2017/09/30)

Reductive fractionation of woody biomass into lignin monomers and cellulose by tandem metal triflate and Pd/C catalysis
A catalytic process for the upgrading of woody biomass into mono-aromatics, hemi-cellulose sugars and a solid cellulose-rich carbohydrate residue is presented. Lignin fragments are extracted from the lignocellulosic matrix by cleavage of ester and ether linkages between lignin and carbohydrates by the catalytic action of homogeneous Lewis acid metal triflates in methanol. The released lignin fragments are converted into lignin monomers by the combined catalytic action of Pd/C and metal triflates in hydrogen. The mechanism of ether bond cleavage is investigated by lignin dimer models (benzyl phenyl ether, guaiacylglycerol-β-guaiacyl ether, 2-phenylethyl phenyl ether and 2-phenoxy-1-phenylethanol). Metal triflates are involved in cleaving not only ester and ether linkages between lignin and the carbohydrates but also β-O-4 ether linkages within the aromatic lignin structure. Metal triflates are more active for β-O-4 ether bond cleavage than Pd/C. On the other hand, Pd/C is required for cleaving α-O-4, 4-O-5 and β-β linkages. Insight into the synergy between Pd/C and metal triflates allowed optimizing the reductive fractionation process. Under optimized conditions, 55 wt% mono-aromatics-mainly alkylmethoxyphenols-can be obtained from the lignin fraction (23.8 wt%) of birch wood in a reaction system comprising birch wood, methanol and small amounts of Pd/C and Al(III)-triflate as catalysts. The promise of scale-up of this process is demonstrated.
Huang, Xiaoming,Morales Gonzalez, Olivia M.,Zhu, Jiadong,Korányi, Tamás I.,Boot, Michael D.,Hensen, Emiel J. M.
p. 175 - 187
(2017/01/24)

Investigate cleavage of β-O-4 linkage in lignin model compounds by aerobic oxidation of Cα and Cγ hydroxyl groups
The selective cleavage of common linkages in lignin polymers is a promising approach to generate valuable aromatic hydrocarbons. Herein, we found that on oxidation of Cα and Cγ hydroxyl groups in β-O-4 lignin model compounds with TEMPO catalyst resulted in the formation of 1,3-dicarbonyl TEMPO adduct. These oxidized products readily underwent fragmentation at Cα-Cβ bond in the presence of a catalytic amount of acid to generate corresponding carboxylic acid and phenol monomers.
Patil, Nikhil D.,Yan, Ning
supporting information
p. 3024 - 3028
(2016/07/06)

Precise oxygen scission of lignin derived aryl ethers to quantitatively produce aromatic hydrocarbons in water
To produce aromatic hydrocarbons from biomass, a novel route is reported for one-pot selective hydrodeoxygenation of a lignin derived aryl ether mixture to C6-C9 aromatic hydrocarbons over Ru/sulfate zirconia in the aqueous phase. The cascade steps undergo the initial precise cleavage of the Caliphatic-O bond of phenolic dimers or Caromatic-OCH3 of phenolic monomers, as well as the full blockage of benzene-ring and cyclic-alkene hydrogenation to realize nearly quantitative aromatic hydrocarbon formation at 240 °C in the presence of low pressurized H2 (2-8 bar). With a Ru catalyst, the primary and competitive steps in hydrogenolysis of the C-O bond and hydrogenation of the benzene ring are shown to be sensitive to temperature and hydrogen pressure, which can subtly modify the concentration and spatial distribution of the surface adsorbed H. A high temperature and a low hydrogen pressure are found to be essential for hydrogenolysis, since the H species nearby the oxygen atom are more strongly adsorbed under such conditions and thus preferred to be retained on the Ru surface. Herein it is defined as the "atom-induced H sorption effect", probably resulting from the analogous hydrogen-bond force between the adsorbed H and the adjacent oxygen atom on the metal surface. Besides the initial step, another key point for aromatic hydrocarbon formation is to optimize the target route of cycloalkene dehydrogenation, but suppress the parallel hydrogenation pathway to saturated cycloalkanes. It is found that the produced phenol intermediate serves as a suitable H-acceptor for the selected catalytic system during the whole conversion, via fast consumption of the in situ produced H from cyclohexene dehydrogenation. Such an interesting phenomenon of internal hydrogen transfer not only promotes the dehydrogenation and hydrogenation equilibrium of cyclohexene but also lowers the in situ H concentration on the Ru surface, both of which would be beneficial for reaching a high benzene yield. This hypothesis for internal hydrogen transfer is further confirmed by separate experiments and density functional theory modelling results.
Luo, Zhicheng,Wang, Yimeng,He, Mingyuan,Zhao, Chen
supporting information
p. 433 - 441
(2016/01/30)

Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
supporting information
p. 6545 - 6555
(2018/06/06)

Facile and selective hydrogenolysis of β-O-4 linkages in lignin catalyzed by Pd-Ni bimetallic nanoparticles supported on ZrO2
The β-O-4 linkage in lignin can be selectively cleaved by Pd-Ni bimetallic nanoparticles supported on ZrO2 using hydrogen gas as the hydrogen donor under ambient pressure and neutral conditions. Conspicuous enhancement in activity is observed compared with single nickel and palladium catalysts based on the results of experiments and characterization. Moreover, hydrogenation of the produced phenols is tuned by adjusting the amount of NaBH4. The catalyst can be reused over ten times in the model reaction and over five times in the hydrogenolysis of lignin without an obvious change in activity and selectivity.
Zhang, Jia-Wei,Cai, Yao,Lu, Guo-Ping,Cai, Chun
p. 6229 - 6235
(2016/12/03)

From insertion to multicomponent coupling: Temperature dependent reactions of arynes with aliphatic alcohols
The temperature dependent selectivity switch in the reaction of arynes with aliphatic alcohols in THF has been reported. At -20°C, arynes smoothly insert into the O-H bond of alcohols to form alkyl aryl ethers. Interestingly, at 60°C, a highly selective multicomponent coupling occurs with the solvent THF acting as the nucleophilic trigger affording (4-(alkoxy)butoxy)arenes.
Thangaraj, Manikandan,Bhojgude, Sachin Suresh,Mane, Manoj V.,Biju, Akkattu T.
supporting information
p. 1665 - 1668
(2016/01/30)

Selective hydrogenolysis of phenols and phenyl ethers to arenes through direct C-O cleavage over ruthenium-tungsten bifunctional catalysts
Direct hydrogenolysis of the aromatic Csp2-O bonds in both phenols and phenyl ethers to form arenes selectively is a core enabling technology that can expand greatly the scope of chemical manufacture from biomass. However, conventional hydrogenolysis of phenols typically led to aromatic ring saturation instead of the cleavage of the Csp2-O bonds. Herein, we report a recyclable Ru-WOx bifunctional catalyst that showed high catalytic activities for the hydrogenolysis of a wide range of phenols and phenyl ethers, including dimeric lignin model compounds and the primitive phenols separated from pyrolysis lignin, to form arenes selectively in water. Preliminary mechanistic studies supported that the reactions occurred via a direct cleavage of the Csp2-O bonds and the concerted effects of the hydrogenating Ru sites and the Lewis acidic W sites are the key to such an unusual reactivity.
Huang, Yao-Bing,Yan, Long,Chen, Meng-Yuan,Guo, Qing-Xiang,Fu, Yao
p. 3010 - 3017
(2015/05/27)

Direct production of naphthenes and paraffins from lignin
The utilization of lignin as a fuel precursor has attracted attention, and a novel and facile process has been developed for one-pot conversion of lignin into cycloalkanes and alkanes with Ni catalysts under moderate conditions. This cascade hydrodeoxygenation approach may open the route to a new promising technique for direct liquefaction of lignin to hydrocarbons.
Kong, Jiechen,He, Mingyuan,Lercher, Johannes A.,Zhao, Chen
supporting information
p. 17580 - 17583
(2015/12/08)

Copper-catalyzed O-arylation of N-protected 1,2-aminoalcohols using functionalized trivalent organobismuth reagents
The O-arylation of 1,2-aminoalcohols using functionalized triarylbismuth reagents is reported. The reaction can be performed using substoichiometric amounts of copper acetate and operates under mild conditions. Good functional group tolerance is observed, giving access to a range of β-aryloxyamines. The effect provided by the amino group in the arylation reaction is investigated.
Petiot, Pauline,Dansereau, Julien,Hbert, Martin,Khene, Imene,Ahmad, Tabinda,Samaali, Samira,Leroy, Maxime,Pinsonneault, Francis,Legault, Claude Y.,Gagnon, Alexandre
supporting information
p. 1322 - 1327
(2015/01/30)

Mild and Robust Redox-Neutral Pd/C-Catalyzed Lignol β-O-4′ Bond Cleavage Through a Low-Energy-Barrier Pathway
A Pd/C catalyzed redox neutral C - O bond cleavage of 2-aryloxy-1-arylethanols has been developed. The reactions are carried out at 80 °C, in air, using a green solvent system to yield the aryl ketones in near quantitative yields. Addition of catalytic amounts of a hydrogen source to the reaction mixture activates the catalyst to proceed through a low energy barrier pathway. Initial studies support a transfer hydrogenolysis reaction mechanism that proceeds through an initial dehydrogenation followed by an enol adsorption to Pd/C and a reductive C - O bond cleavage.
Galkin, Maxim V.,Dahlstrand, Christian,Samec, Joseph S. M.
p. 2187 - 2192
(2015/07/15)

A clean and selective radical homocoupling employing carboxylic acids with titania photoredox catalysis
A titania photoredox catalysis protocol was developed for the homocoupling of C-centered radicals derived from carboxylic acids. Intermolecular reactions were generally efficient and selective, furnishing the desired dimers in good yields under mild neutral conditions. Selective cross-coupling with two acids proved unsuccessful. An intra-molecular adaptation enabled macrocycles to be prepared, albeit in modest yields. (Chemical Equation Presented).
Manley, David W.,Walton, John C.
supporting information
p. 5394 - 5397
(2015/02/19)

A series of NiM (M = Ru, Rh, and Pd) bimetallic catalysts for effective lignin hydrogenolysis in water
In this paper, NiRu, NiRh, and NiPd catalysts were synthesized and evaluated in the hydrogenolysis of lignin C-O bonds, which is proved to be superior over single-component catalysts. The optimized NiRu catalyst contains 85% Ni and 15% Ru, composed of Ni surface-enriched, Ru-Ni atomically mixed, ultrasmall nanoparticles. The Ni85Ru15 catalyst showed high activity under low temperature (100°C), low H2 pressure (1 bar) in β-O-4 type C-O bond hydrogenolysis. It also exhibited significantly higher activity over Ni and Ru catalysts in the direct conversion of lignin into monomeric aromatic chemicals. Mechanistic investigation indicates that the synergistic effect of NiRu can be attributed to three factors: (1) increased fraction of surface atoms (compared with Ni), (2) enhanced H2 and substrate activation (compared with Ni), and (3) inhibited benzene ring hydrogenation (compared with Ru). Similarly, NiRh and NiPd catalysts were more active and selective than their single-component counterparts in the hydrogenolysis of lignin model compounds and real lignin.
Zhang, Jiaguang,Teo, Jason,Chen, Xi,Asakura, Hiroyuki,Tanaka, Tsunehiro,Teramura, Kentaro,Yan, Ning
p. 1574 - 1583
(2014/05/20)

Highly efficient, NiAu-catalyzed hydrogenolysis of lignin into phenolic chemicals
A highly efficient, stable NiAu catalyst that exhibits unprecedented low temperature activity in lignin hydrogenolysis was for the first time developed, leading to the formation of 14 wt% aromatic monomers from organosolv lignin at 170 °C in pure water. the Partner Organisations 2014.
Zhang, Jiaguang,Asakura, Hiroyuki,Van Rijn, Jeaphianne,Yang, Jun,Duchesne, Paul,Zhang, Bin,Chen, Xi,Zhang, Peng,Saeys, Mark,Yan, Ning
supporting information
p. 2432 - 2437
(2014/05/06)

Room temperature, metal-free arylation of aliphatic alcohols
Diaryliodonium salts are demonstrated as efficient arylating agents of aliphatic alcohols under metal-free conditions. The reaction proceeds at room temperature within 90 min to give alkyl aryl ethers in good to excellent yields. Aryl groups with electron
Ghosh, Raju,Lindstedt, Erik,Jalalian, Nazli,Olofsson, Berit
p. 54 - 57
(2014/05/06)

Mild heterogeneous palladium-catalyzed cleavage of β-o-4'-ether linkages of lignin model compounds and native lignin in air
A mild and robust heterogeneous palladium-catalyzed C - O bond cleavage of 2-aryloxy-1-arylethanols using formic acid as reducing agent in air was developed. The cleaved products were isolated in 92-98 % yield; and by slightly varying the reaction conditions, a ketone, an alcohol, or an alkane can be generated in near-quantitative yield. This reaction is applicable to cleaving the β-O-4'-ether bond found in lignin polymers of different origin. The reaction was performed on a lignin polymer model to generate either the monomeric aryl ketone or alkane in a quantitative yield. Moderate depolymerization was achieved with native lignin at similar reaction conditions. Mechanistic studies under kinetic control indicate that an initial palladium-catalyzed dehydrogenation of the alcohol is followed by insertion of palladium to an enol equivalent. A palladium-formato complex reductively cleaves the palladium-enolate complex to generate the ketone. Copyright
Galkin, Maxim V.,Sawadjoon, Supaporn,Rohde, Volker,Dawange, Monali,Samec, Joseph S. M.
p. 179 - 184
(2014/01/23)

Hydrogenation and cleavage of the C-O bonds in the lignin model compound phenethyl phenyl ether over a nickel-based catalyst
Phenethyl phenyl ether (PPE) was selected as a typical lignin model compound and hydrogenated and cleaved over two readily accessible nickel-based catalysts, which could be easily separated from the product mixture. The results revealed that the reduction of the nickel catalyst with gaseous hydrogen produced a species capable of achieving higher activity towards C-O-C bond cleavage compared to the Ru/C and Pd/C catalysts. The selectivity of the C-O-C bond cleavage over the Ni/C catalyst was 85%, and higher than the corresponding values in the Ru/C (40%) and Pd/C (69%) systems. Using the carbothermal reduction method for the production of the Ni/C-C catalyst, the conversion and selectivity levels reached 99%, with 40% of the benzene rings in PPE being reserved. In comparison, no benzene ring containing products wer observed over the noble metal catalysts. This difference was attributed to the interaction between the carbon support and the nickel nanoparticles.
Song, Qi,Cai, Jiaying,Zhang, Junjie,Yu, Weiqiang,Wang, Feng,Xu, Jie
p. 651 - 658
(2013/07/11)

Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(ii) complexes containing functionalized tripodal amine-pyrazolyl ligands
Structurally distinctive dinuclear Ni(ii) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'- tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(ii) TMEDA and Mg(ii) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(ii) and Mg(ii) bimetallic species have also been identified in the ESI-MS spectra.
Xue, Fei,Zhao, Jin,Hor, T. S. Andy
p. 5150 - 5158
(2013/04/10)

Process for Production of Carboxylic Acid Ester or Ether Compound
Disclosed is a process for production of a carboxylic acid ester from a carboxylic acid and an olefin or production of an ether compound from an alcohol and an olefin at low cost and with high yield in an industrially advantageous manner. The process comprises the step of reacting a carboxylic acid with an olefin to yield a corresponding carboxylic acid ester or reacting an alcohol with an olefin to yield a corresponding ether compound. In the process, a catalyst comprising a combination of (i) at least one metal compound selected from an iron compound, a cobalt compound and a nickel compound and (ii) an acidic compound is used.
-
Page/Page column 7

(2009/01/24)

Intramolecular assistance of electron transfer from heteroatom compounds. Electrochemical oxidation of 2-(2-pyridyl)ethyl-substituted ethers, sulfides, and selenides
Organoheteroatom compounds having a 2-(2-pyridyl)ethyl group were synthesized and their oxidation potentials were determined by rotating disk electrode voltammetry. The oxidation potentials were found to be less positive than those of the corresponding compounds having a phenyl group in place of the pyridyl group. The dynamic coordination of the pyridyl group to the heteroatom, which stabilizes the cation radical intermediate, seems to be responsible for facilitating the electron transfer. The magnitude of the intramolecular assistance increases along with an increase in the oxidation potential of the parent compounds. This tendency can be explained in terms of the energy match between the nonbonding p orbital of the pyridyl nitrogen and the HOMO of the parent heteroatom compound.
Watanabe, Mitsuru,Suga, Seiji,Yoshida, Jun-Ichi
p. 243 - 247
(2007/10/03)

Thermolysis of Phenethyl Phenyl Ether: A Model Ether Linkages in Lignin and Low Rank Coal
The thermolysis of phenethyl phenyl ether (PPE) was studied at 330-425 deg C to resolve the discrepancies in the reported mechanisms of this important model of the β-ether linkage found in lignin and low rank coal.Cracking of PPE proceeded by two competit
Britt, Phillip F.,Buchanan, A. C.,Malcolm, Elizabeth A.
p. 6523 - 6536
(2007/10/03)

ONE ELECTRON OXIDATION OF BENZYL AND 2-PHENYLETHYL PHENYL ETHERS. THE FATE OF THE INTERMEDIATE RADICAL CATIONS
The one electron oxidations of benzyl phenyl ether (1), 2-phenylethyl phenyl ether (2) and 2-(4-methoxyphenyl)ethyl phenyl ether (3) promoted (a) by cerium(IV) ammonium nitrate (CAN) in AcOH, (b) electrochemically in AcOH-MeCN/AcOK and (c) photochemically in MeCN, in the presence of 9,10-dicyanoanthracene (DCA), have been investigated.With 1 benzaldehyde forms, under all the reaction conditions, accompanied by products of acetoxylation at the phenoxy ring (conditions a and b) or by phenyl benzoate (condition c).The CAN-promoted and the electochemical oxidation of 2 exclusively lead to substitution at the phenoxy ring, whereas only side-chain attack at the benzylic carbon occurs in all of the reactions of 3, with formation of 4-methoxybenzaldehyde and products of side-chain oxidation.Phenyl 4-methoxybenzoate is also formed (conditions b and c).However, when the electrochemical oxidation is carried out in the absence of AcOK, only a product of intermolecular ring closure forms.These results allow one to draw some interesting conclusion on the competition between the various reaction pathways available to the cation radicals which are the first formed reaction intermediates in these one electron processes.
Baciocchi, Enrico,Piermattei, Alessandro,Rol, Cesare,Ruzziconi, Renzo,Sebastiani, Giovanni Vittorio
p. 7049 - 7062
(2007/10/02)

SYNTHETIC APPLICATION OF MICELLAR CATALYSIS. WILLIAMSON'S SYNTHESIS OF ETHERS
A simple, rapid and efficient procedure for the preparation of di-alkyl, simple phenyl-alkyl and hindered phenyl-alkyl ethers has been developed.Based on the principle of micellar catalysis the method involves alkylation of the alkoxide or the phenoxide ion with an alkyl chloride at 80 deg C in the presence of cationic micelles.For the preparation of phenyl-alkyl ethers normal micelles were used, while for the di-alkyl ethers reverse micelles were more effective.By increasing the ionic strength of the solution the rate of formation of phenyl-alkyl ethers could be increased.
Jursic, Branko
p. 6677 - 6680
(2007/10/02)

The Chemistry of Pentavalent Organobismuth Reagents. Part 8. Phenylation and Oxidation of Alcohols by Tetraphenylbismuth Esters
Tetraphenylbismuth trifluoroacetate under neutral or slightly acidic conditions O-phenylates primary alcohols in reasonable (65-75percent) yield, but gives only moderate yields with secondary alcohols and no O-phenylation with tertiary alcohols.An SN2 type mechanism is proposed with attack of oxygen on aryl carbon.In contrast, the reaction of Bi(V) reagents with alcohols under basic conditions gives, exclusively, oxidation, often with benzene as a leaving group.The presence of a Bi(V) intermediate with a bismuth-oxygen bond has been proved in several different ways using n.m.r. spectroscopy.Thus the reactions of alcohols with Bi(V) reagents parallel the corresponding reactions with phenols.
Barton, Derek H. R.,Finet, Jean-Pierre,Motherwell, William B.,Pichon, Clotilde
p. 251 - 260
(2007/10/02)

Ion-Molecule Complexes in Unimolecular Fragmentations of Gaseous Cations. Alkyl Phenyl Ether Molecular Ions
A decomposition pathway that bears a formal resemblance to first-order elimination in solution is demonstrated for parent ion fragmentations of alkyl phenyl ethers under electron impact (EI) and chemical ionization (CI).The sequence of steps in the gas phase, parent ion -> ion-molecule complex -> fragments, is analogous to first-order elimination in solution (which goes through ion pairs).Such a mechanism for expulsion of PhOH+. from molecular ions has been tested by examing neutral products from 70-eV electron bombardment of neopentyl phenyl ether in a specially constructed electron bombardment flow (EBFlow) reactor.The C5H10 isomers 2-methyl-1-butene (2) and 2-methyl-2-butene (3) are recovered in the same ratio (2/3=1.14) as is produced by gas-phase deprotonation of tert-amyl cation.This result is validated by a mass spectrometric study of deuterated analogues, for which the ratio of γ-transfer (corresponding to product 2) to α-transfer (corresponding to product 3) is calculated to be 1.46.Intermediacy of an ion-molecule complex, PhOCH2C(CH3)3+. -> .CH3CH2(CH3)2C+> -> PhOH+. + 2 or 3, predicts this outcome, where the species in brackets represents an electrostatically bound comlex of the neutral phenoxyl radical and an alkyl cation.This mechanism explains the published mass spectrometric (EI an CI) and EBFlow results for n-propyl and n-butyl phenyl ethers.Several confirmatory experiments support the intermediacy of an ion-molecule complex and rule out other interpretations of the experiment data.
Morton, Thomas Hellman
p. 1596 - 1602
(2007/10/02)