- Copper(II)-catalyzed O-phenylation of alcohols with organobismuth(V) reagents: A convenient method for the synthesis of simple tert-alkyl phenyl ethers
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A convenient method for copper(II)-catalyzed O-phenylation of simple alcohols with organobismuth(V) compounds under mild conditions is described. Treatment of tetraphenylbismuth fluoride (Ph4BiF) with various simple alcohols in the presence of
- Mukaiyama, Teruaki,Sakurai, Naoto,Ikegai, Kazuhiro
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- Synthesis of orderly nanoporous aluminophosphate and zirconium phosphate materials and their catalytic applications
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Amorphous alumino phosphate (AP) and zirconium phosphate (ZP) materials possessing an ordered nanoporosity have been successfully synthesized by a hydrothermal method using a P123 block co-polymer as the structure directing agent. The materials exhibited excellent catalytic activity towards selective alkylation of phenol with cyclohexanol, where AP showed as high as 100% selectivity to produce the industrially important O-alkylation product, while the corresponding ZP selectively produced a C-alkylation product (93% selectivity). This journal is the Partner Organisations 2014.
- Sreenivasulu, Peta,Viswanadham, Nagabhatla,Sharma, Trymbkesh,Sreedhar
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- Rational synthesis of palladium nanoparticles modified by phosphorous for the conversion of diphenyl ether to KA oil
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Conversion of lignin-derived molecules into value-added chemicals is critical for sustainable chemistry but still challenging. Herein, phosphorus-modified palladium catalyzed the degradation of lignin-derived 4-O-5 linkage to produce KA oil (cyclohexanone-cyclohexanol oil) was reported. The reaction proceeds via a restricted partial hydrogenation-hydrolysis pathway. Phosphorus-modified palladium catalyst suppressed the full hydrogenation of diary ether, which was the key point to produce KA oil selectively. Under the optimized conditions, the 4.5 nm Pd-P NPs could catalyze the conversion of 4-O-5 linkage into KA oil in 83% selectivity with a high production rate of 32.5 mmol·g?1Pd·min?1. This study represented an original method for KA oil production.
- Bai, Hong-Cun,Cao, Jing-Pei,Jiang, Wei,Wei, Yu-Lei,Xie, Jin-Xuan,Zhang, Chuang,Zhao, Liang,Zhao, Ming,Zhao, Xiao-Yan
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- Rh-PVP Catalyzed Reductive Amination of Phenols by Ammonia or Amines to Cyclohexylamines under Solvent-free Conditions
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Colloidal metal nanoparticles were examined for reductive amination of phenol by ammonia under mild reaction conditions. The results showed that Rh-PVP was the most active catalyst for reductive amination reaction. Linear, cyclic, and amino alcohols were used as nucleophiles and converted to primary/secondary/tertiary amines. Using this strategy, the synthesis of an industrially important chemical, N-cyclohexyl- 2-pyrrolidone was explored.
- Chaudhari, Chandan,Nagaoka, Katsutoshi,Nishida, Yoshihide,Rumi, Saeki,Sato, Katsutoshi,Shiraishi, Masaya
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supporting information
p. 81 - 84
(2022/01/12)
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- Hydrodeoxygenation of Lignin-Derived Aromatic Oxygenates Over Pd-Fe Bimetallic Catalyst: A Mechanistic Study of Direct C–O Bond Cleavage and Direct Ring Hydrogenation
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Hydrodeoxygenation of lignin-derived phenols could be achieved generally with three reaction pathways: tautomerization, direct ring hydrogenation and direct C–O bond cleavage. The former pathway has been extensively studied over Pd/Fe catalyst in liquid-phase reaction, however, the contribution of the latter two is yet subject to further investigations. In this report, a comparative study of direct C–O bond cleavage and direct ring hydrogenation reaction pathways is presented on Pd/Fe, Fe and Pd/C catalysts using diphenyl ether as modelling compound. Despite its much higher activation energy than direct ring hydrogenation, direct C–O bond cleavage is dominant over Pd/Fe with much higher rates than the monometallic analogues due to the synergic catalysis of Pd–Fe. Based on this study and our previous results, the detailed reaction network for HDO of diphenyl ether is proposed. Graphic Abstract: [Figure not available: see fulltext.]
- Zhang, Jianghao,Sudduth, Berlin,Sun, Junming,Wang, Yong
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p. 932 - 939
(2020/09/02)
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- Radical Anion Promoted Chemoselective Cleavage of Csp2-S Bond Enables Formal Cross-Coupling of Aryl Methyl Sulfones with Alcohols
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A novel formal cross-coupling of aryl methyl sulfones and alcohols affording alkyl aryl ethers via an SRN1 pathway is developed. Two marketed antitubercular drugs were efficiently prepared employing this approach as the key step. A dimsyl-anion initiated radical chain process was revealed as the major pathway. DFT calculations indicate that the formation of a radical anion via nucleophilic addition of alkoxide to the aryl radical is the key step in determining the observed chemoselectivity.
- Bai, Jixiang,Wang, Tianxin,Dai, Botao,Liu, Qingchao,Yu, Peiyuan,Jia, Tiezheng
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supporting information
p. 5761 - 5765
(2021/08/16)
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- Hydrogenolysis of aromatic ethers under lignin-first conditions
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The cleavage of the etheric C–O bond in diphenyl ether (DPE), phenethyl phenyl ether (PPE) and benzyl-phenyl ether (BPE) has been investigated by using Ru/C (5% wt) and Pd/C (5% wt), as heterogeneous catalysts, under reaction conditions generally adopted for the reductive catalytic fractionalization of lignocellulosic biomasses (lignin-first approach). Catalytic tests were carried out in the presence of simple C1-C3 alcoholic H-donor solvents (methanol, ethanol and 2-propanol) used as such or in mixture with water in the temperature range of 120–240 °C both in the presence or in the absence of molecular hydrogen as reducing agent. Under transfer hydrogenolysis conditions, the Ru/C catalyst was found to be the best performing system in the cleavage of the 4–O–5 etheric C–O bond (95 % DPE conversion in 2-propanol at 210 °C after 3 h of reaction) with a less pronounced tendency in hydrogenating the aromatic ring. Upon increasing the water content in the reaction medium, a decrease in the cleavage of the C–O bond of DPE together with a higher production of phenolics is observed as a consequence of the reductive hydrolysis reaction occurrence. The best yield in aromatic compounds (52 %) was obtained by using as solvent a water/2-propanol (75:25, v/v) mixture in absence of added molecular hydrogen, with the alcoholic fraction being the in-situ H-source. A lower tendency to undergo to hydrolysis reaction together with a higher production of aromatics is registered in the case of phenethyl phenyl ether and benzyl-phenyl ether. Results are explained in terms of the higher steric hindrance of PPE and BPE with respect to DPE and of the competitive adsorption of arenes arising from hydrogenolysis of etheric β–O–4 and α–O–4 bonds (phenol + ethyl benzene or phenol + toluene) on the Ru/C catalyst surface.
- Beneduci, A.,Corrente, G. A.,Malara, A.,Mauriello, F.,Paone, E.
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- CoII Immobilized on Aminated Magnetic-Based Metal–Organic Framework: An Efficient Heterogeneous Nanostructured Catalyst for the C–O Cross-Coupling Reaction in Solvent-Free Conditions
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Abstract: In this paper, we report the synthesis of Fe3O4?AMCA-MIL53(Al)-NH2-CoII NPs based on the metal–organic framework structures as a magnetically separable and environmentally friendly heterogeneous nanocatalyst. The prepared nanostructured catalyst efficiently promotes the C–O cross-coupling reaction in solvent-free conditions without the need for using toxic solvents and/or expensive palladium catalyst. Graphic Abstract: [Figure not available: see fulltext.].
- Mohammadinezhad, Arezou,Akhlaghinia, Batool
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p. 332 - 352
(2020/01/11)
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- Liquid-phase hydrodeoxygenation of lignin-derived phenolics on Pd/Fe: A mechanistic study
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Although Pd/Fe bimetallic catalysts have been extensively studied in vapor-phase hydrodeoxygenation of phenolics (i.e., guaiacol, cresol), little is yet known about their performance in liquid-phase reactions. In this work, we present a mechanistic study on the Pd/Fe bimetallic catalysts in liquid-phase hydrodeoxygenation of phenolics. The role of tautomerization in hydrodeoxygenation of the lignin-derived phenolics, particularly for ring saturation, is systematically studied by employing two representative modeling compounds: phenol (a molecule that is keto-enol tautomeric) and diphenyl ether (a molecule that does not allow ketol-enol tautomerization). It was found that although the addition of oxyphilic Fe inhibits the direct aromatic ring saturation reaction typically occurring on Pd, tautomerization opens another reaction pathway toward ring saturation products (i.e. cyclohexanone, cyclohexanol, cyclohexane et al.), where both tautomerization and the hydrogenation of keto isomers are significantly enhanced to produce cyclohexanol followed by direct hydrogenolysis of the cyclohexanol to cyclohexane.
- Zhang, Jianghao,Sun, Junming,Sudduth, Berlin,Pereira Hernandez, Xavier,Wang, Yong
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p. 305 - 311
(2019/01/04)
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- Base-Mediated O-Arylation of Alcohols and Phenols by Triarylsulfonium Triflates
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A mild and efficient protocol for O-arylation of alcohols and phenols (ROH) by triarylsulfonium triflates was developed under transition-metal-free conditions. Various alcohols, including primary, secondary and tertiary, and phenols bearing either electron-donating or electron-withdrawing groups on the aryl rings were smoothly converted to form the corresponding aromatic ethers in moderate to excellent yields. The reactions were conducted at 50 or 80 °C for 24 h in the presence of a certain base and showed good functional group tolerance. The base-mediated arylation with asymmetric triarylsulfonium salts could selectively transfer the aryl groups of sulfoniums to ROH, depending on their inherent electronic nature. The mechanistic studies revealed that the reaction might proceed through the nucleophilic attack of the in situ formed alkoxy or phenoxy anions at the aromatic carbon atoms of the C?S bonds of triarylsulfonium cations to furnish the target products.
- Ming, Xiao-Xia,Tian, Ze-Yu,Zhang, Cheng-Pan
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supporting information
p. 3370 - 3379
(2019/11/03)
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- Selective cleavage of lignin and lignin model compounds without external hydrogen, catalyzed by heterogeneous nickel catalysts
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Selective hydrogenolysis of the Caryl-O bonds in lignin is a key strategy for the generation of fuels and chemical feedstocks from biomass. Currently, hydrogenolysis has been mainly conducted using hydrogen, which is flammable and not sustainable or economical. Herein, an external hydrogen-free process for aryl ethers hydrogenolysis in lignin models and dioxasolv lignin over nickel nanoparticles supported on Al2O3, is reported. Kinetic studies reveal that the transfer hydrogenolysis activity of the three model compounds decreased in the following order: benzyl phenyl ether (α-O-4), 2-phenylethyl phenyl ether (β-O-4) and diphenyl ether (4-O-5), which linearly corresponds to their binding energies and the activation energies. The main reaction route for the three model compounds was the cleavage of the ether bonds to produce aromatic alkanes and phenol, and the latter was further reduced to cyclohexanol. Dioxasolv lignin depolymerization results exhibit a significant Caryl-O decrease over the Ni nanoparticles supported on Al2O3 with iso-propanol as the hydrogen source through 2D-HSQC-NMR analysis, which confirmed the transfer hydrogenolysis conclusion in the model study. This work provides an economical and environmentally-friendly method for the selective cleavage of lignin and lignin model compounds into value-added chemicals.
- Jiang, Liang,Guo, Haiwei,Li, Changzhi,Zhou, Peng,Zhang, Zehui
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p. 4458 - 4468
(2019/04/29)
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- Palladium-Catalyzed Formal Cross-Coupling of Diaryl Ethers with Amines: Slicing the 4-O-5 Linkage in Lignin Models
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Lignin is the second most abundant organic matter on Earth, and is an underutilized renewable source for valuable aromatic chemicals. For future sustainable production of aromatic compounds, it is highly desirable to convert lignin into value-added platform chemicals instead of using fossil-based resources. Lignins are aromatic polymers linked by three types of ether bonds (α-O-4, β-O-4, and 4-O-5 linkages) and other C?C bonds. Among the ether bonds, the bond dissociation energy of the 4-O-5 linkage is the highest and the most challenging to cleave. To date, 4-O-5 ether linkage model compounds have been cleaved to obtain phenol, cyclohexane, cyclohexanone, and cyclohexanol. The first example of direct formal cross-coupling of diaryl ether 4-O-5 linkage models with amines is reported, in which dual C(Ar)?O bond cleavages form valuable nitrogen-containing derivatives.
- Zeng, Huiying,Cao, Dawei,Qiu, Zihang,Li, Chao-Jun
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supporting information
p. 3752 - 3757
(2018/03/13)
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- Rh(CAAC)-Catalyzed Arene Hydrogenation: Evidence for Nanocatalysis and Sterically Controlled Site-Selective Hydrogenation
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We report the arene hydrogenation of ethers, amides, and esters at room temperature and low hydrogen pressure, starting from [(CAAC)Rh(COD)Cl] (CAAC = cyclic alkyl amino carbene). Kinetic, mechanistic, and Rh K-edge XAFS studies showed formation of Rh nanoparticles from [(CAAC)Rh(COD)Cl], in contrast to a previous report of [(CAAC)Rh(COD)Cl] functioning as a homogeneous catalyst for arene hydrogenation. We determined that the site-selective arene hydrogenation catalyzed by this system is under steric control, as shown by detailed competition experiments with derivatives of ethers, amides, and esters bearing different aromatic rings of varying electronic and steric influence. This work illustrates the potential of CAAC ligands in the formation and stabilization of a colloidal dispersion of stable nanoparticle catalysts.
- Tran, Ba L.,Fulton, John L.,Linehan, John C.,Lercher, Johannes A.,Bullock, R. Morris
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p. 8441 - 8449
(2018/08/17)
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- Decarboxylative C(sp3)?O Cross-Coupling
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Alkyl aryl ethers are an important class of compounds in medicinal and agricultural chemistry. Catalytic C(sp3)?O cross-coupling of alkyl electrophiles with phenols is an unexplored disconnection strategy to the synthesis of alkyl aryl ethers, with the potential to overcome some of the major limitations of existing methods such as C(sp2)?O cross-coupling and SN2 reactions. Reported here is a tandem photoredox and copper catalysis to achieve decarboxylative C(sp3)?O coupling of alkyl N-hydroxyphthalimide (NHPI) esters with phenols under mild reaction conditions. This method was used to synthesize a diverse set of alkyl aryl ethers using readily available alkyl carboxylic acids, including many natural products and drug molecules. Complementarity in scope and functional-group tolerance to existing methods was demonstrated.
- Mao, Runze,Balon, Jonathan,Hu, Xile
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supporting information
p. 13624 - 13628
(2018/09/25)
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- Formal Cross-Coupling of Diaryl Ethers with Ammonia by Dual C(Ar)-O Bond Cleavages
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The conversion of renewable resources and inexpensive inorganic chemicals directly into higher value-added organic chemicals is becoming more and more important for our society's future sustainable development. Lignin, being the second most abundant organic carbon renewable resource on Earth, has been treated as waste in the pulp and paper industry. The 4-O-5 linkage diaryl ether bond is the strongest among the three types of ether linkages in lignins. Selective cleavage of this linkage can potentially generate smaller processable bio-based aromatic polymeric materials and compounds. Furthermore, there has been a long synthetic interest in coupling reactions with aryl ethers via C(Ar)-O bond cleavage, for example, for polyphenylene oxide (PPO) waste recycling. On the other hand, ammonia is a very inexpensive industrial inorganic chemical. Herein, we report a direct conversion of diaryl ethers and ammonia into aniline derivatives and arenes, providing a model for selective lignin 4-O-5 linkage modification and PPO recycling with inexpensive ammonia. Both symmetrical and unsymmetrical diaryl ethers were successfully cross-coupled with ammonia via dual C(Ar)-O bond cleavages, generating the corresponding cyclohexylanilines and arenes.
- Cao, Dawei,Zeng, Huiying,Li, Chao-Jun
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p. 8873 - 8878
(2018/09/12)
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- Effective Utilization of Flow Chemistry: Use of Unstable Intermediates, Inhibition of Side Reactions, and Scale-Up for Boronic Acid Synthesis
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Flow chemistry processes for boronic acid syntheses utilizing lithiation-borylation have been developed. The side reactions in the lithiation step that occur in batch were suppressed, and unstable lithium intermediates were handled safely. Flow technology was applied to several kinds of boronic acid syntheses, and scale-up was successfully conducted to allow kilogram-scale production. Some of the key benefits of flow flash chemistry were utilized, both to avoid side reactions and to enable dianion chemistry that is difficult to perform successfully in batch reactions. The examples showed further perspectives on the utility of flow technologies for process development.
- Usutani, Hirotsugu,Cork, David G.
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p. 741 - 746
(2018/06/11)
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- Efficient cleavage of aryl ether C-O linkages by Rh-Ni and Ru-Ni nanoscale catalysts operating in water
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Bimetallic Ru-Ni and Rh-Ni nanocatalysts coated with a phase transfer agent efficiently cleave aryl ether C-O linkages in water in the presence of hydrogen. For dimeric substrates with weaker C-O linkages, i.e. α-O-4 and β-O-4 bonds, low loadings of the precious metal (Rh or Ru) in the nanocatalysts quantitatively afford monomers, whereas for the stronger 4-O-5 linkage higher amounts of the precious metal are required to achieve complete conversion. Under the optimized, relatively mild operating conditions, the C-O bonds in a range of substituted ether compounds are efficiently cleaved, and mechanistic insights into the reaction pathways are provided. This work paves the way to sustainable approaches for the hydrogenolysis of C-O bonds.
- Bulut, Safak,Siankevich, Sviatlana,Van Muyden, Antoine P.,Alexander, Duncan T. L.,Savoglidis, Georgios,Zhang, Jiaguang,Hatzimanikatis, Vassily,Yan, Ning,Dyson, Paul J.
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p. 5530 - 5535
(2018/07/06)
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- Palladium-Catalyzed Reductive Insertion of Alcohols into Aryl Ether Bonds
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Palladium on carbon catalyzes C?O bond cleavage of aryl ethers (diphenyl ether and cyclohexyl phenyl ether) by alcohols (R?OH) in H2. The aromatic C?O bond is cleaved by reductive solvolysis, which is initiated by Pd-catalyzed partial hydrogenation of one phenyl ring to form an enol ether. The enol ether reacts rapidly with alcohols to form a ketal, which generates 1-cyclohexenyl?O?R by eliminating phenol or an alkanol. Subsequent hydrogenation leads to cyclohexyl?O?R.
- Wang, Meng,Gutiérrez, Oliver Y.,Camaioni, Donald M.,Lercher, Johannes A.
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p. 3747 - 3751
(2018/03/21)
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- Metal-Free I2-Catalyzed Highly Selective Dehydrogenative Coupling of Alcohols and Cyclohexenones
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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
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p. 233 - 240
(2018/02/19)
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- Nanocrystalline hierarchical ZSM-5: An efficient catalyst for the alkylation of phenol with cyclohexene
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In this paper, authors report the synthesis of nanocrystalline hierarchical zeolite ZSM-5 and its application as a heterogeneous catalyst in the alkylation of phenol with cyclohexene. The catalyst was synthesized by vacuum-concentration coupled hydrothermal technique in the presence of two templates. This synthetic route could successfully introduce pores of higher hierarchy in the zeolite ZSM-5 structure. Hierarchical ZSM-5 could catalyse effectively the industrially important reaction of cyclohexene with phenol. We ascribe the high efficiency of the catalyst to its conducive structural features such as nanoscale size, high surface area, presence of hierarchy of pores and existence of Lewis sites along with Br?nsted acid sites. The effect of various reaction parameters like duration, catalyst amount, reactant mole ratio and temperature were assessed. Under optimum reaction conditions, the catalyst showed up to 65% selectivity towards the major product, cyclohexyl phenyl ether. There was no discernible decline in percent conversion or selectivity even when the catalyst was re-used for up to four runs. Kinetic studies were done through regression analysis and a mechanistic route based on LHHW model was suggested.
- Radhika,Selvin, Rosilda,Kakkar, Rita,Roselin, L. Selva
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p. 5404 - 5413
(2018/02/28)
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- Hydrogenolysis/hydrogenation of diphenyl ether as a model decomposition reaction of lignin from biomass in pressurized CO2/water condition
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Catalytic hydrogenolysis of the C[sbnd]O bond of diphenyl ether (a lignin model compound) was investigated as a function of hydrogen pressure in scCO2 medium in the presence of water. Using commercially available Rh/C catalyst, the C[sbnd]O bond cleavage of diphenyl ether mainly results phenolic monomer at 80 °C. Hydrogen pressure is one of the key parameters because (i) C[sbnd]O bond cleavage and the hydrogenation of aromatic rings are two competitive reactions; very sensitive to hydrogen pressure and (ii) hydrogen has complete solubility in scCO2. Therefore, a critical control of hydrogen pressure was essential to reach the targeted cleavage of the C[sbnd]O bond when the reaction was conducted in scCO2 medium under pressurized condition. Depending on the hydrogen pressure, a significant change in the ratio of monocyclic:bicyclic products from 91:9 (0.2 MPa) to 58:42 (2 MPa) was revealed in the shortest reaction time of 5 min. Thus, low hydrogen pressure was the effective choice for the scission of the C[sbnd]O bond, whereas higher hydrogen pressure hydrogenate the aromatic ring due to the higher coverage of hydrogen on the catalytic surface. Amount of the catalyst (catalyst:substrate ratio) displayed a subtle effect on the breakage of the C[sbnd]O bond. A threshold ratio of 1:5 was preferred under the present reaction condition as the increased amount hampered the substrate:water ratio and hydrogenation of the aromatic ring occurred. In addition, as the change in temperature is associated with the change in the physical properties of scCO2, hence, the effect on the transformation of DPE was complicated and difficult to explain. Furthermore, different organic solvents as neat, along with CO2 and with water also has substantial impact on the rapture of C[sbnd]O bond. The obtained results from the solvent studies again proved that scCO2 along with water was the best choice for C[sbnd]O bond breakage and water is the driving force to mediate the reaction. In addition, a combination catalyst (Ni+Rh) was also tested for the same reaction under the similar working condition. Preliminary results suggested a synergistic effect in terms of the selectivity of monocyclic compounds.
- Chatterjee, Maya,Ishizaka, Takayuki,Kawanami, Hajime
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p. 402 - 409
(2016/12/14)
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- Palladium-Catalyzed Hydrolytic Cleavage of Aromatic C?O Bonds
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Metallic palladium surfaces are highly selective in promoting the reductive hydrolysis of aromatic ethers in aqueous phase at relatively mild temperatures and pressures of H2. At quantitative conversions, the selectivity to hydrolysis products of PhOR ethers was observed to range from 50 % (R=Ph) to greater than 90 % (R=n-C4H9, cyclohexyl, and PhCH2CH2). By analysis of the evolution of products with and without incorporation of H218O, the pathway was concluded to be initiated by palladium metal catalyzed partial hydrogenation of the phenyl group to an enol ether. Water then rapidly adds to the enol ether to form a hemiacetal, which then undergoes elimination to cyclohexanone and phenol/alkanol products. A remarkable feature of the reaction is that the stronger Ph?O bond is cleaved rather than the weaker aliphatic O?R bond.
- Wang, Meng,Shi, Hui,Camaioni, Donald M.,Lercher, Johannes A.
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supporting information
p. 2110 - 2114
(2017/02/15)
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- Conversion of Cyclohexanones to Alkyl Aryl Ethers by Using a Pd/C–Ethylene System
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The conversion of cyclohexanone and substituted cyclohexanones into alkyl aryl ethers by using a Pd/C–ethylene system is discussed, with ethylene functioning as a hydrogen acceptor. The ether products are easily transformed into the corresponding phenols by treatment with BBr3. The direct conversion of cyclohexenone into phenol in the presence of a catalytic amount of Pd/C under an ethylene atmosphere is also described.
- El-Deeb, Ibrahim Yussif,Tian, Miaomiao,Funakoshi, Tatsuya,Matsubara, Ryosuke,Hayashi, Masahiko
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p. 409 - 413
(2017/01/24)
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- ZnCl2 induced catalytic conversion of softwood lignin to aromatics and hydrocarbons
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Selective cleavage of C-O-C bonds in lignin without disrupting the C-C linkages can result in releasing aromatic monomers and dimers that can be subsequently converted into chemicals and fuels. Results from this study showed that both biomass-derived lignin and lignin model compounds were depolymerized in a highly concentrated ZnCl2 solution under relatively mild conditions (120 °C-200 °C, 4-6 h). Zn2+ ions in highly concentrated ZnCl2 aqueous solutions appeared to selectively coordinate with C-O-C bonds to cause the key linkages of lignin to be much easier to cleave under mild conditions. In a 63 wt% ZnCl2 solution at 200 °C for 6 h, nearly half of the softwood technical lignin was converted to oil products, of which the majority were alkylphenols. Results indicated that most of the β-O-4 and Cmethyl-OAr bonds of the lignin model compounds were cleaved under the above reaction conditions, providing a foundation towards understanding lignin depolymerization in a concentrated ZnCl2 solution. Furthermore, by adding Ru/C as a co-catalyst, the phenolic products were further converted into more stable cyclic hydrocarbons via hydrodeoxygenation and coupling reactions.
- Wang, Hongliang,Zhang, Libing,Deng, Tiansheng,Ruan, Hao,Hou, Xianglin,Cort, John R.,Yang, Bin
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p. 2802 - 2810
(2016/05/24)
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- Bifunctional Ni catalysts for the one-pot conversion of Organosolv lignin into cycloalkanes
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In this report, Ni/ZrO2, Ni/Al2O3, Ni/Al2O3-KF, Ni/SBA-15, and Ni/Al-SBA-15 were examined as catalysts for the hydrodeoxygenation of diphenyl ether. Adopting the degree of deoxygenation and yield of monocyclic products as the criteria for the catalyst selection, Ni/Al-SBA-15 was identified as the best catalyst for HDO of diphenyl ether. In fact, in the presence of Ni/Al-SBA-15, full conversion of the model compound into cyclohexane was achieved with high selectivity (98%). Most strikingly, Ni/Al-SBA-15 is capable of hydrodeoxygenating Organosolv lignin with selectivity to cycloalkanes higher than 99%. Owing to the similarities to hydrocarbons derived from petroleum, the lignin-derived alkanes could well be refined into drop-in fuels by conventional oil refinery processes. Moreover, in a broader perspective, the current results also highlight the importance of Al-SBA-15, as an acidic support alternative to zeolites or other acidic materials, for the HDO of phenolic streams.
- Wang, Xingyu,Rinaldi, Roberto
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- Chemo- and Regioselective Hydrogenolysis of Diaryl Ether C-O Bonds by a Robust Heterogeneous Ni/C Catalyst: Applications to the Cleavage of Complex Lignin-Related Fragments
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We report the chemo- and regioselective hydrogenolysis of the C-O bonds in di-ortho-substituted diaryl ethers under the catalysis of a supported nickel catalyst. The catalyst comprises heterogeneous nickel particles supported on activated carbon and furnishes arenes and phenols in high yields without hydrogenation. The high thermal stability of the embedded metal particles allows C-O bond cleavage to occur in highly substituted diaryl ether units akin to those in lignin. Preliminary mechanistic experiments show that this catalyst undergoes sintering less readily than previously reported catalyst particles that form from a solution of [Ni(cod)2].
- Gao, Fang,Webb, Jonathan D.,Hartwig, John F.
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supporting information
p. 1474 - 1478
(2016/02/12)
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- Copper Catalyzed sp3 C-H Etherification with Acyl Protected Phenols
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A variety of acyl protected phenols AcOAr participate in sp3 C-H etherification of substrates R-H to give alkyl aryl ethers R-OAr employing tBuOOtBu as oxidant with copper(I) β-diketiminato catalysts [CuI]. Although 1°, 2°, and 3° C-H bonds may be functionalized, selectivity studies reveal a preference for the construction of hindered, 3° C-OAr bonds. Mechanistic studies indicate that β-diketiminato copper(II) phenolates [CuII]-OAr play a key role in this C-O bond forming reaction, formed via transesterification of AcOAr with [CuII]-OtBu intermediates generated upon reaction of [CuI] with tBuOOtBu.
- Salvador, Tolani K.,Arnett, Charles H.,Kundu, Subrata,Sapiezynski, Nicholas G.,Bertke, Jeffery A.,Raghibi Boroujeni, Mahdi,Warren, Timothy H.
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supporting information
p. 16580 - 16583
(2017/01/10)
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- Air-stable palladium(0) phosphine sulfide catalysts for Ullmann-type C-N and C-O coupling reactions
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This paper describes an efficient procedure for palladium(0)-catalyzed N-arylation and O-arylation of aryl halides by Ullmann-type cross coupling reaction under mild reaction conditions in a short reaction time. Two phosphine sulphide ligands and their corresponding Pd(0) complexes namely [Pd(p2S2)(dba)] and [Pd(pp3S4)(dba)], were synthesized, where p2S2 is 1,2-bis(diphenylphosphino)ethane disulfide, pp3S4 is tris[2-(diphenylphosphino)ethyl]phosphine tetrasulfide and dba is dibenzylideneacetone. Optimal reaction conditions were determined for the arylation reactions using iodobenzene and benzimidazole by varying temperature, solvent, base and catalyst loading. The cross coupling reactions were carried out taking iodobenzenes/bromobenzenes and a wide variety of substituted aryl amines/phenols/alcohols with different steric and electronic properties to afford the desired N-aryl amines/diaryl ethers/alkyl aryl ethers in good to excellent yield (70-94%).
- Majumder, Arpi,Gupta, Ragini,Mandal, Mrinmay,Babu, Madhu,Chakraborty, Debashis
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- Chemoselective O-Versus C-Alkylation of substituted phenols with cyclohexene over mesoporous ZSM-5
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Chemoselective O- versus C-alkylation of substituted phenols such as phenol, p-cresol, and guaiacol with cyclohexene were investigated over various ZSM-5 catalysts with different degree of mesoporosity and external acidity such as mesoporous ZSM-5 synthesized by microwave induced assembly via electrostatic interaction between sulfonic acid, functionalized or non-functionalized ZSM-5 nanozeolites and counter cationic surfactant, and hydrothermal synthesized microporous ZSM-5 with or without sulfonic acid functionalization and surfactant. The selectivity of O- and C-alkylated products varied with different degree of mesoporosity. The selectivity of C-alkylated products increased with increasing mesopore volume and external acid sites, whereas that of O-alkylated product decreased. The mesoporous ZSM-5 synthesized under microwave via sulfonic acid functionalization showed not only the highest mesoporosity and external acid sites but also the best catalytic activity and selectivity of C-alkylated products, whereas the other ZSM-5 catalysts mainly produced O-alkylated products due to diffusion limitation of bulky product.
- Jin, Hailian,Ansari, Mohd Bismillah,Park, Sang-Eon
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p. 184 - 190
(2014/02/14)
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- Titanium nitride-nickel nanocomposite as heterogeneous catalyst for the hydrogenolysis of aryl ethers
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Lignin from biomass can become a sustainable source of aromatic compounds. Its depolymerization can be accomplished through hydrogenolysis, although the development of catalysts based on cheap and abundant metals is lacking. Herein, a sustainable composite based on titanium nitride and nickel is synthesized and employed as catalyst for the hydrogenolysis of aryl ethers as models for lignin. The catalytic activity of the new material during hydrogenation reactions is proven to be superior to that of either component alone. In particular, different aryl ethers could be efficiently converted under relatively mild conditions into aromatic compounds and cycloalkanes within minutes.
- Molinari, Valerio,Giordano, Cristina,Antonietti, Markus,Esposito, Davide
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supporting information
p. 1758 - 1761
(2014/03/21)
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- Hydrogenation of phenols in ionic liquids on rhodium nanoparticles
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A new catalyst system based on rhodium nanoparticles stabilized by polyacrylic acid have been suggested for the hydrogenation of phenols in ionic liquids. It has been shown that high near-quantitative yields of reaction products are achieved in ionic liquids containing a tetraalkylammonium cation. By the TEM and XPS techniques it has been revealed that the use of ionic liquids substantially decreases the particle size and reduces the aggregation of nanoparticles through the inclusion of the ionic liquid cations into the surface layer along with polyacrylic acid.
- Maksimov,Kuklin,Kardasheva,Karakhanov
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p. 157 - 163
(2013/07/27)
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- CATALYTIC C-H BOND ACTIVATION FOR THE SYNTHESIS OF ETHERS AND THIOETHERS
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Disclosed is a method for the transition metal-mediated oxidation of C-H bonds to form C-0 or C-S bonds. The methods are useful for the formation of ethers (R-OR') from alcohols, R'OH, and sp3 -hybridized C-H bonds in substrates, R-H. Aryl or heteroaryl acetates may also be used for C-H to C-OAr bond formation. The methods are also useful in the preparation of C-S bonds from acetyl-protected thiols, MeC(0)SR, and disulfides, RSSR. Advantageously, the methods minimize reaction steps, the handling of oxidized intermediates, and environmental impact.
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Page/Page column 5; 46-47
(2014/01/08)
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- Heterogeneous palladium-catalyzed synthesis of aromatic ethers by solvent-free dehydrogenative aromatization: Mechanism, scope, and limitations under aerobic and non-aerobic conditions
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Starting from cyclohexanone derivatives and alcohols, both non-aromatic precursors, aryl ethers could be synthesized in good yields and with good selectivities in the presence of a catalytic amount of Pd/C, in one step, without added solvent, in a reaction vessel open to air. For less reactive substrates, the addition of 1-octene in a closed system under non-aerobic conditions improved the conversion. In addition, the catalyst could be recycled several times with no decrease in the yield of the aryl ether. The process was also used with tetralone derivatives and polyols. Several reactions were performed to propose a mechanism for this transformation. The formation of an enol ether followed by a dehydrogenation reaction seem to be the key steps of this reaction. Aryl ethers were prepared in good yields and with good selectivities in a solvent-free and heterogeneous catalytic dehydrogenative alkylation of cyclohexanones with various alcohols. Three different complementary routes were used, and for the first time, non-aerobic, safe conditions could be used. Moreover, the catalyst could be recycled several times with no decrease in the yield of the aryl ether. Copyright
- Sutter, Marc,Lafon, Romain,Raoul, Yann,Metay, Estelle,Lemaire, Marc
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supporting information
p. 5902 - 5916
(2013/09/23)
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- An efficient cleavage of the aryl ether C-O bond in supercritical carbon dioxide-water
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A simple and highly efficient Rh/C catalyzed route for the cleavage of the C-O bond of aromatic ether at 80 °C in the presence of 0.5 MPa of H 2 in the scCO2-water medium is reported; CO2 pressure and water play a key role under the tested conditions.
- Chatterjee, Maya,Ishizaka, Takayuki,Suzuki, Akira,Kawanami, Hajime
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supporting information
p. 4567 - 4569
(2013/06/04)
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- Kinetics and mechanism of acid catalyzed alkylation of phenol with cyclohexene in the presence of styrene divinylbenzene sulfonic resins
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The kinetics of phenol cyclohexylation catalyzed by sulfonic resins is studied taking into account equilibria and side reactions observed in the reaction media. The influence of different sulfonic resins has been tested and only small variation of the catalyst activity, referred to the acid amount, has been observed. Besides, the selectivity is unaffected by varying the type of the catalyst. The effect of reagent concentration on the reaction rate has been also studied, together with the reactivity of the cyclohexyl phenyl ether as intermediate. The etherification equilibrium of cyclohexyl phenyl ether has been analyzed in the presence of methanesulfonic acid, and the adsorption equilibria on a sulfonic resin of reagents and intermediates are measured, too. Starting from the evidences obtained from these studies an Eley-Rideal type kinetic model has been proposed and the fitting of the experimental data allows obtaining the kinetic constant of each stage. Good reliability of the model with the experimental data has been observed, also at high conversion, and the values of the fitting parameters are substantially constant by varying the operative variable, which is a further proof of the goodness of the model.
- Ronchin,Quartarone,Vavasori
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experimental part
p. 192 - 203
(2012/03/09)
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- Ni-catalyzed cleavage of aryl ethers in the aqueous phase
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A novel Ni/SiO2-catalyzed route for selective cleavage of ether bonds of (lignin-derived) aromatic ethers and hydrogenation of the oxygen-containing intermediates at 120 C in presence of 6 bar H2 in the aqueous phase is reported. The C-O bonds of α-O-4 and β-O-4 linkages are cleaved by hydrogenolysis on Ni, while the C-O bond of the 4-O-5 linkage is cleaved via parallel hydrogenolysis and hydrolysis. The difference is attributed to the fact that the Caliphatic-OH fragments generated from hydrolysis of α-O-4 and β-O-4 linkages can undergo further hydrogenolysis, while phenol (produced by hydrolysis of the 4-O-5 linkage) is hydrogenated to produce cyclohexanol under conditions investigated. The apparent activation energies, Ea(α-O-4) a(β-O-4) a(4-O-5), vary proportionally with the bond dissociation energies. In the conversion of β-O-4 and 4-O-5 ether bonds, C-O bond cleavage is the rate-determining step, with the reactants competing with hydrogen for active sites, leading to a maximum reaction rate as a function of the H2 pressure. For the very fast C-O bond cleavage of the α-O-4 linkage, increasing the H2 pressure increases the rate-determining product desorption under the conditions tested.
- He, Jiayue,Zhao, Chen,Lercher, Johannes A.
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p. 20768 - 20775
(2013/02/22)
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- Solvent effects on the hydrogenolysis of diphenyl ether with raney nickel and their implications for the conversion of lignin
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The conversion of lignin, the most recalcitrant of the biopolymers, is necessary for a carbon-efficient utilization of lignocellulosic materials. In this context, hydrogenolysis of lignin is a process receiving increasing attention. In this report, the solvent effects on the hydrogenolysis of diphenyl ether and lignin with Raney Ni are addressed. The Lewis basicity of the solvent very much affects the catalytic activity, so Raney Ni in nonbasic solvents is an extremely active catalyst for hydrogenolysis and hydrogenation. In basic solvents, however, Raney Ni is a less active, but much more selective catalyst for hydrogenolysis while preserving the aromatic products. With regard to the reactions with lignin, assessing the complexity of the product mixtures by two-dimensional GC×GC-MS revealed solvent effects on the product distribution. Reaction in methylcyclohexane resulted in cyclic alcohols and cyclic alkanes, whereas reaction in 2-propanol led to cyclic alcohols, cyclic ketones, and unsaturated products. The hydrogenolysis of lignin in methanol, however, produced mostly phenols. Overall, these results demonstrate that the solvent plays a key role in directing the selectivity and, thus, it must be taken into consideration in the design of catalytic systems for conversion of lignin by hydrogenolysis of C-O ether bonds. Copyright
- Wang, Xingyu,Rinaldi, Roberto
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scheme or table
p. 1455 - 1466
(2012/10/07)
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- A heterogeneous nickel catalyst for the hydrogenolysis of aryl ethers without arene hydrogenation
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A heterogeneous nickel catalyst for the selective hydrogenolysis of aryl ethers to arenes and alcohols generated without an added dative ligand is described. The catalyst is formed in situ from the well-defined soluble nickel precursor Ni(COD)2 or Ni(CH2TMS)2(TMEDA) in the presence of a base additive, such as tBuONa. The catalyst selectively cleaves CAr-O bonds in aryl ether models of lignin without hydrogenation of aromatic rings, and it operates at loadings down to 0.25 mol % at 1 bar of H2 pressure. The selectivity of this catalyst for electronically varied aryl ethers differs from that of the homogeneous catalyst reported previously, implying that the two catalysts are distinct from each other.
- Sergeev, Alexey G.,Webb, Jonathan D.,Hartwig, John F.
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supporting information
p. 20226 - 20229
(2013/02/25)
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- Catalytic aerobic synthesis of aromatic ethers from non-aromatic precursors
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Only little waste: Aryl ether formation is accomplished by oxidative condensation of alcohols and 2-cyclohexenones. The reaction complements the existing methods used by synthetic chemists to obtain aryl ethers, and allows a straightforward access to a wide range of functionalized products. In addition, the catalytic reaction with O2 as the oxidant generates water as the only by-product and provides a greener approach to aryl ethers. Copyright
- Simon, Marc-Olivier,Girard, Simon A.,Li, Chao-Jun
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supporting information; experimental part
p. 7537 - 7540
(2012/09/10)
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- Acid catalyzed alkylation of phenols with cyclohexene: Comparison between homogeneous and heterogeneous catalysis, influence of cyclohexyl phenyl ether equilibrium and of the substituent on reaction rate and selectivity
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The reactivity of several phenols toward liquid phase alkylation with cyclohexene in the presence of heterogeneous and homogeneous acid catalyst at 358 K is studied. The comparison between Amberlyst 15 and CH3SO 3H, as examples of heterogeneous and homogeneous systems, shows a higher activity of the former with different behavior of selectivity between the two systems, anyway, in both systems O-alkylation and ring alkylations occur. A remarkable difference in the selectivity of the ring alkylation between heterogeneous and homogeneous systems is observed: Amberlyst 15 shows a constant ortho/para ratio close to 2, while in the presence of CH3SO 3H ortho/para is variable from 3 to 5, suggesting an involvement of the cyclohexyl phenyl ether rearrangement. This is proved also by a direct relationship between the ortho/para ratio and the concentration of the cyclohexyl phenyl ether when CH3SO3H is used as a catalyst. The formation of cyclohexyl aryl ethers is reversible; on the contrary, ring alkylation appears irreversible. The reactivity of the dimethylphenols shows a strong influence of the steric hindrance of the substituent on the electrophilic attack of the cyclohexyl cation, which is poorly influenced by the inductive effect of the methyl group.
- Ronchin,Vavasori,Toniolo
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scheme or table
p. 134 - 141
(2012/03/09)
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- DEHYDROGENATION OF CYCLOHEXANONE TO PRODUCE PHENOL
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In a process for the dehydrogenation of cyclohexanone to produce phenol, a feed comprising cyclohexanone is contacted with a dehydrogenation catalyst under dehydrogenation conditions comprising a temperature of less than 4000C and a pressure of less than 690 kPa, gauge, such 0.1 to 50 wt% of the cyclohexanone in said feed is converted to phenol and the dehydrogenation product contains less than 100 ppm by weight of alkylbenzenes.
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Page/Page column 22; 25
(2011/09/14)
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- Starbon acids in alkylation and acetylation reactions: Effect of the Broensted-Lewis acidity
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Various Starbon supported solid acids were prepared and investigated in two test reactions, namely the acetylation of 5-acetyl-methylsalicylate and the alkylation of phenol with cyclohexene. Starbon-SO3H materials exhibited in general an optimum balance of Lewis and Bronsted acid sites, making them ideal catalysts for the investigated processes. Starbon acids were comparably active and differently selective compared to similar solid acids utilised in the proposed acid catalysed processes including commercial sulphated zirconia and beta zeolite. Materials were also highly reusable under the different reaction conditions, preserving their activities almost unchanged after 4 reuses.
- Luque, Rafael,Budarin, Vitaly,Clark, James H.,Shuttleworth, Peter,White, Robin J.
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experimental part
p. 1471 - 1476
(2012/07/03)
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- Rhodium/graphite-catalyzed hydrogenation of carbocyclic and heterocyclic aromatic compounds
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Rhodium on graphite (Rh/Gr, C24Rh) was prepared by reaction of anhydrous rhodium trichloride with potassium graphite (C8K, 3 equivalents) and used as a heterogeneous catalyst for the hydrogenation of carbocyclic and heterocyclic aromatic compounds at room temperature and 1 atm of hydrogen pressure. The effect of substitution on the benzene ring was examined in a variety of derivatives, including those with alkyl, hydroxy, alkoxy, aryloxy, carboxy, amino, nitro, acyl, chloro, or functionalized alkyl groups. Reduction of carbonyl functions of aromatic aldehydes and ketones occurred with complete or partial cleavage of the benzylic C-O bond; this cleavage also occurred in the hydrogenation of benzylic alcohols and esters. Georg Thieme Verlag Stuttgart.
- Falini, Giuseppe,Gualandi, Andrea,Savoia, Diego
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experimental part
p. 2440 - 2446
(2010/02/27)
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- An efficient Ullmann-type C-O bond formation catalyzed by an air-stable copper(I)-bipyridyl complex
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(Chemical Equation Presented) An efficient O-arylation of phenols and aliphatic alcohols with aryl halides was developed that uses an air-stable copper(I) complex as the catalyst. This arylation reaction can be performed in good yield in the absence of Cs2CO3. A variety of functional groups are compatible with these reaction conditions with low catalyst loading levels.
- Niu, Jiajia,Zhou, Hua,Li, Zhigang,Xu, Jingwei,Hu, Shaojing
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p. 7814 - 7817
(2008/12/22)
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- Hydroamination and hydroalkoxylation catalyzed by triflic acid. Parallels to reactions initiated with metal triflates
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(Chemical Equation Presented) Intermolecular additions of the O-H bonds of phenols and alcohols and the N-H bonds of sulfonamides and benzamide to olefins catalyzed by 1 mol % of triflic acid and studies to define the relationship between these reactions and those catalyzed by metal triflates are reported. Cyclization of an alcohol containing pendant monosubstituted and trisubstituted olefins catalyzed by either triflic acid or metal triflates form products from addition to the more substituted olefin, and additions of tosylamide catalyzed by triflic acid or metal triflates form indistinguishable ratios of the two N-alkyl sulfonamides.
- Rosenfeld, Devon C.,Shekhar, Shashank,Takemiya, Akihiro,Utsunomiya, Masaru,Hartwig, John F.
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p. 4179 - 4182
(2007/10/03)
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- Copper-catalyzed etherification of aryl iodides using KF/Al 2O3: An improved protocol
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A simple and efficient method for the coupling of aryl iodides with aliphatic alcohols and phenols that does not require the use of alkoxide bases is described. This C-O bond forming procedure shows that the combination of air stable CuI and 1,10-phenanthroline in the presence of KF/Al2O 3 comprises an extremely efficient and general catalyst system for the etherification of aryl iodides. Different functionalized aryl iodides were coupled with alcohols and phenols using this method.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Alikarami, Mohammad
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p. 1101 - 1104
(2007/10/03)
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- Synthesis of cyclohexylphenols
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Catalytic alkylation of phenols with cyclohexanol gives o- and p-cyclohexylphenols as the major products. The effect of temperature, catalyst nature, and reactant concentration on the reaction outcome was studied.
- Postnova,Koshel',Lebedeva,Kuznetsova,Koshel'
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p. 1415 - 1417
(2007/10/03)
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- Copper(II)-catalyzed ether synthesis from aliphatic alcohols and potassium organotrifluoroborate salts
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(Matrix presented) A protocol for the copper(II)-catalyzed etherification of aliphatic alcohols under mild and essentially neutral conditions is described. Air- and moisture-stable potassium alkenyl- and aryltrifluoroborate salts undergo cross-coupling with a variety of aliphatic primary and secondary alcohols and phenols, and are tolerant of a range of functional groups. The optimized conditions utilize catalytic copper(II) acetate with 4-(dimethylamino)pyridine as ligand in the presence of 4 A molecular sieves under an atmosphere of oxygen.
- Quach, Tan D.,Batey, Robert A.
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p. 1381 - 1384
(2007/10/03)
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- Spiro-fysed 2-alkoxy-2-amino-Δ3-1,3,4-oxadiazolines. Synthesis and thermolysis to corresponding aminooxycarbenes
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Δ3-1,3,4-Oxadiazolines spiro-fused at C2 to C2 to oxazolidines (12) or to C2 of tetrahydro-1,3-oxazines (13) were synthesized. The oxadiazolines undergo thermolysis in benzene at 90°C with first-order rate constants of (1.6-50) × 10-5 s-1. The dependence of these rate constants on the nature of the substituents present on the oxadiazoline ring is consistent with a mechanism involving a carbonyl ylide intermediate. Substituents on N of the oxazolidine or tetrahydro-1,3-oxazine moieties play a major role in determining the fragmentation pathways. Oxadiazolines with N-carbonyl groups (12c-j, 13d,e) afford essentially quantitative yields of the corresponding aminooxycarbenes, while other fragmentation reactions compete with carbene generation in the case of oxadiazolines with N-methyl (12b, 13c) or N-sulfonyl (12k) groups.
- Couture, Philippe,Warkentin, John
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p. 1264 - 1280
(2007/10/03)
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