- Fabricating Bifunctional Co?Al2O3@USY Catalyst via In-Situ Growth Method for Mild Hydrodeoxygenation of Lignin to Naphthenes
-
To enhance the catalytic activity and stability of metal catalysts in the hydrodeoxygenation of lignin derivatives into naphthenes, a bifunctional Co?Al2O3@USY catalyst was fabricated by the reduction of CoAl layered double hydroxide in-situ grown on the USY zeolite. In the hydrodeoxygenation of guaiacol, a 100.0 % conversion with cyclohexane yield up to 93.6 % was achieved at 180 °C, 3 MPa for 4 h, which should be the hitherto lowest reaction temperature that has been reported over Co-based metal catalysts. This catalyst was also relatively stable with 5 runs and exhibited excellent catalytic performance in the hydrodeoxygenation of other lignin model compounds and even real lignin feedstock into naphthenes. The high-efficiency of Co?Al2O3@USY was attributed to the synergistic effect between well-dispersed small Co nanoparticles and abundant acidic sites on the USY surface, while the outstanding stability was attributed to the anchoring effect of Al2O3 matrix to Co nanoparticles which avoided the leaching of Co species and particle agglomeration. This work provides a potential strategy for the design of an efficient and stable catalyst for lignin utilization.
- Cheng, Shuai,Diao, Xinyong,Ji, Na,Jia, Zhichao,Li, Hanyang,Ri, Poknam,Wang, Shurong
-
-
- Role of Catalyst Support's Physicochemical Properties on Catalytic Transfer Hydrogenation over Palladium Catalysts
-
Catalytic transfer hydrogenation (CTH) is a promising reaction for valorisation of bio-based feedstocks via hydrogenation without needing to use H2. Unlike standard hydrogenation, CTH occurs via dehydrogenation (DHD) of a hydrogen donor (H-donor) and hydrogenation (HYD) of a substrate. Therefore, the “ideal” CTH catalyst must balance the catalysis of both reactions to maximize the hydrogen transfer between H-donor and substrate with minimal H2 loss to gas (high atom efficiency). Additionally, the H-donor must be highly stable to prevent secondary reactions with the substrate. Herein we study the impact of the catalyst's properties on CTH of guaiacol using bicyclohexyl, a liquid organic hydrogen carrier, as a H-donor. The reaction was promoted by palladium dispersed on three typical support materials (γ-Al2O3, MgO, and SiO2). The performance of these catalysts in the conversion of bicyclohexyl and guaiacol was evaluated, allowing to estimate the H-transfer efficiency, as well as the potential for recycling the spent H-donor (bicyclohexyl). The apparent activation energies for DHD of bicyclohexyl and HYD of guaiacol revealed that slow DHD combined with fast HYD, as is the case with Pd/MgO, favours hydrogen transfer efficiency and selectivity towards hydrogenated products. In addition, an investigation of the DHD of bicyclohexyl and HYD of guaiacol independently showed that the affinity between the organic molecules and the support significantly impacts CTH. Indeed, Pd/SiO2 was highly active for both reactions individually and almost inactive for CTH. Consequently, these findings highlight the importance of the interaction between solvent-substrate-support in designing catalysts for transfer hydrogenation.
- Batalha, Nuno,Fraga, Gabriel,Hasan, M. D.,Konarova, Muxina,Laycock, Bronwyn,Pratt, Steven,Santos, Mirella S.
-
p. 5191 - 5202
(2021/10/29)
-
- Hollow, mesoporous, eutectic Zn1?xMgxO nano-spheres as solid acid-base catalysts for the highly regio-selectiveO-methylation of 1,2-diphenols
-
The highly regio-selectiveO-methylation of catechol with dimethyl carbonate (DMC), catalyzed by a solid acid-base catalyst, is an environmentally friendly chemical process for industrial production of guaiacol. However, a guaiacol yield below 84% and high reaction temperature above 280 °C limit its industrial application. Here, hollow, mesoporous Zn1?xMgxO nano-spheres with a eutectic structure, denoted as Zn1?xMgxO HMNSs (x= 0.012-0.089), are facilely fabricatedviathe calcination of Mg2+/Zn2+ion-adsorbing carbon spheres at 500 °C in air. In theO-methylation of catechol with DMC at 180 °C, Zn1?xMgxO HMNSs (x= 0.052) afford guaiacol in 95.5% yield with a complete catechol conversion. Furthermore, 89.0-95.3% mono-ether yields with high 1,2-diphenol conversions (94.5-100%) are also obtained for the other 1,2-diphenols bearing -CH3and -Br groups. Moreover, a plausible mechanism for highly selectiveO-methylation of catechol with DMC is proposed, in which the single-site activation and double-site activation of phenolic hydroxyls by the basic oxygen of Mg-O afford guaiacol and veratrole, respectively.
- Liu, Jie,Ma, Xuebing,Wang, Xuri,Xie, Guangxin,Yin, Zuyong,Zhang, Jianing
-
p. 7454 - 7466
(2021/11/23)
-
- Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
-
Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
- Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
-
supporting information
p. 20391 - 20399
(2021/08/13)
-
- Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant
-
A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine (1) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.
- Toriumi, Naoyuki,Yamashita, Kazuya,Iwasawa, Nobuharu
-
supporting information
p. 12635 - 12641
(2021/08/03)
-
- Nickel-Catalyzed Photodehalogenation of Aryl Bromides
-
Herein, we describe a Ni-catalyzed photodehalogenation of aryl bromides under visible-light irradiation that utilizes tetrahydrofuran as hydrogen source. The protocol obviates the need for exogeneous amine reductants or photocatalysts and is characterized by its simplicity and broad scope, including challenging substrate combinations.
- Higginson, Bradley,Sanjosé-Orduna, Jesus,Gu, Yiting,Martin, Ruben
-
supporting information
p. 1633 - 1636
(2021/04/23)
-
- Ceramic boron carbonitrides for unlocking organic halides with visible light
-
Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable. This journal is
- Yuan, Tao,Zheng, Meifang,Antonietti, Markus,Wang, Xinchen
-
p. 6323 - 6332
(2021/05/19)
-
- Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts
-
Dimethyl sulfide, a major byproduct of the Kraft pulping process, was used as an inexpensive and sustainable catalyst/co-reagent (methyl donor) for various methylations with dimethyl carbonate (as both reagent and solvent), which afforded excellent yields of O-methylated phenols and benzoic acids, and mono-C-methylated arylacetonitriles. Furthermore, these products could be isolated using a remarkably straightforward workup and purification procedure, realized by dimethyl sulfide‘s neutral and distillable nature and the absence of residual salts. The likely mechanisms of these methylations were elucidated using experimental and theoretical methods, which revealed that the key step involves the generation of a highly reactive trimethylsulfonium methylcarbonate intermediate. The phenol methylation process represents a rare example of a Williamson-type reaction that occurs without the addition of a Br?nsted base.
- Chan, Bun,Lui, Matthew Y.,Lui, Yuen Wai
-
-
- Dimethoxybenzene and preparation method thereof
-
The invention relates to the field of etherification of organic compounds, and discloses dimethoxybenzene and a preparation method thereof. The method comprises the following steps that 1, in the presence of a catalyst, catechol serves as a raw material, dimethyl carbonate serves as a methylation reagent, a methylation reaction is conducted, and imethoxybenzene is obtained, wherein the catalyst is 1, 8-diazabicyclo [5.4. 0] undec-7-ene; and 2) the reaction product obtained in the step 1) is distilled to recover the dimethyl carbonate, and then reduced pressure distillation is performed to obtain the dimethoxybenzene. According to the method, the green and environment-friendly methylation reagent dimethyl carbonate is adopted, no waste water or solid is generated, the yield is high, and the method is very suitable for industrial production and meets the green and environment-friendly process requirements.
- -
-
Paragraph 0043-0065
(2021/05/29)
-
- One-Pot Synthesis of Papaverine Hydrochloride and Identification of Impurities
-
Abstract: A one-pot synthesis of papaverine hydrochloride with 99.6% purity was performed using xylene as solvent for the entire process. The critical parameters of each step, as well as the impurities generated, were identified. The overall yield was improved to 63%. The proposed synthetic procedure is suitable for industrial production.
- Qiu, Zeng-Feng,Wu, Ze-Nong,Yang, Zhe-Zhou,Yu, Wen-Shuai,Zhang, Fu-Li,Zhao, Chun-Jie
-
p. 1295 - 1299
(2020/09/16)
-
- Cleavage of CC and Co bonds in β-O-4 linkage of lignin model compound by cyclopentadienone group 8 and 9 metal complexes
-
Degradation of 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphe-noxy)propane-1,3-diol (1), a model compound for lignin β-O-4 linkage was examined with iron, ruthenium, rhodium and iridium complexes bearing cyclopentadienone ligand. Cyclopentadienone iron complex gave only a small amount of degraded product with reduced molecular weight. Cyclopentadienone ruthenium complex, so called Shvo's catalyst, afforded 3,4-dimethoxybenzaldehyde (a3) in 14.3% yield after CαCβ bond cleavage. On the other hand, cyclopentadienone group-9 metal complexes catalyzed CβO bond cleavage to afford guaiacol (b1) as a main product in up to 74.9% yield.
- Kishino, Masamichi,Kusumoto, Shuhei,Nozaki, Kyoko
-
supporting information
p. 477 - 480
(2020/05/19)
-
- Soft template-based bismuth doped zinc oxide nanocomposites for photocatalytic depolymerization of lignin
-
Lignin depolymerization is a growing research area for the synthesis of aromatic molecules. In current studies, photocatalytic lignin depolymerization has been investigated by designing a series of soft template-based Zn0.95Bi0.05O nano-materials (SK1-SK5). Synthesized nano-materials were characterized by PXRD, SEM/EDX, BET, FTIR and utilized for photocatalytic lignin depolymerization in the presence of direct sunlight. Lignin depolymerization was monitored by UV–Visible Spectroscopy and catalytic pathway analyzed by different kinetic models. Percent depolymerization was studied for the effect of catalyst dose, starting lignin concentration and different temperatures. Pseudo second order was found the best fitted kinetic model indicating chemically rate controlled mechanism. Activation energy (Ea) for the reaction was found to be 11 kJ/mol that is remarkably lower than conventional lignin depolymerization i.e. 59.75 kJ/mol depicting better catalytic efficiencies of tested materials. Lignin depolymerization products were characterized by HPLC and FTIR Spectroscopy and their analysis indicated the conversion of lignin into smaller subunits like syringaldehyde, sinapyl alcohol, phthalates, and 4-hydroxy-benzoic acid. Specifically, phenol (21%) and 2-methoxy-4-methylphenol (16%) were detected by GCMS analysis in the products of lignin depolymerization by SK2.
- Kausar, Samia,Ali Altaf, Ataf,Hamayun, Muhammad,Danish, Muhammad,Zubair, Muhammad,Naz, Sumbal,Muhammad, Shabbir,Zaheer, Muhammad,Ullah, Shafiq,Badshah, Amin
-
-
- Discovery and characterization of an acridine radical photoreductant
-
Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction1–4. This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper5,6. Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts7–11. Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of ?3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported12. Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants.
- MacKenzie, Ian A.,Wang, Leifeng,Onuska, Nicholas P. R.,Williams, Olivia F.,Begam, Khadiza,Moran, Andrew M.,Dunietz, Barry D.,Nicewicz, David A.
-
-
- Synthesis of Flavanones via Palladium(II)-Catalyzed One-Pot β-Arylation of Chromanones with Arylboronic Acids
-
A total of 47 flavanones were expediently synthesized via one-pot β-arylation of chromanones, a class of simple ketones possessing chemically unactivated β sites, with arylboronic acids via tandem palladium(II) catalysis. This reaction provides a novel route to various flavanones, including natural products such as naringenin trimethyl ether, in yields up to 92percent.
- Cho, Yang Yil,Jang, Hyu Jeong,Kim, Dong Hwan,Kim, Nam Yong,Kim, Nam-Jung,Kim, Young Min,Lee, Soo Jin,Lee, Yong Sup,Park, Boyoung Y.,Son, Seung Hwan,Yoo, Hyung-Seok
-
supporting information
p. 10012 - 10023
(2019/08/30)
-
- Hydrodehalogenation of Aryl Halides through Direct Electrolysis
-
A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu3N/Et3N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale.
- Ke, Jie,Wang, Hongling,Zhou, Liejin,Mou, Chengli,Zhang, Jingjie,Pan, Lutai,Chi, Yonggui Robin
-
supporting information
p. 6911 - 6914
(2019/05/10)
-
- Role of copper- or cerium-promoters on NiMo/Γ-Al2O3 catalysts in hydrodeoxygenation of guaiacol and bio-oil
-
Effect of copper (Cu) or cerium (Ce) as promoters for nickel-molybdenum/γ-alumina (NiMo/γ-Al2O3) catalyst on the hydrodeoxygenation (HDO) of guaiacol (GUA), a model oxygenated compound found in a bio-oil derived from woody biomass, was comparatively investigated. The addition of Cu- or Ce-promoters affected the physicochemical properties of the NiMo catalyst. The NiMo catalyst promoted by Cu showed the higher reducibility, whilst the Ce-promoter (2–8 wt% based on γ-Al2O3 content) provided the NiMo catalyst with a higher distribution of active metals and induced a greater difficulty in the reduction under hydrogen (H2) atmosphere. For the HDO of GUA at a mild reaction condition (10 bar initial H2 pressure and 300 °C) in the absence of solvent, the Cu-promoter enhanced the hydrogenation activity of the NiMo catalyst to convert GUA to phenol and methylphenols, one-atomic oxygen species. Whereas, the addition of Ce obviously inhibited the formation of coke on the catalyst surface after a long reaction period (6 h) and gave a higher GUA conversion level with increasing yield of phenols. For the HDO of real bio-oil obtained from the fast pyrolysis of cassava rhizome, the NiMo catalysts promoted by Cu or Ce at 4 wt% based on the γ-Al2O3 content showed a higher performance at eliminating the oxygenated compounds in the bio-oil, reducing the oxygen/carbon (O/C) molar ratio by over seven-fold from 1.75 to 0.24–0.25. Moreover, the gross heating value of the bio-oil was improved from 21.5 to ca. 29.0 MJ/kg after the HDO process. However, the addition of the Cu or Ce promoter did not inhibit coke deposition, possibly due to the acidic properties of the bio-oil that deteriorated the catalyst performance by metal leaching.
- Sangnikul, Patiphat,Phanpa, Chanisara,Xiao, Rui,Zhang, Huiyan,Reubroycharoen, Prasert,Kuchonthara, Prapan,Vitidsant, Tharapong,Pattiya, Adisak,Hinchiranan, Napida
-
p. 151 - 160
(2019/02/17)
-
- Catalytic Hydrogenolysis of Substituted Diaryl Ethers by Using Ruthenium Nanoparticles on an Acidic Supported Ionic Liquid Phase (Ru@SILP-SO3H)
-
Catalytic hydrogenolysis of diaryl ethers is achieved by using ruthenium nanoparticles immobilized on an acidic supported ionic liquid phase (Ru@SILP-SO 3 H) as a multifunctional catalyst. The catalyst components are assembled through a molecular approach ensuring synergistic action of the metal and acid functions. The resulting catalyst is highly active for the hydrogenolysis of various diaryl ethers. For symmetric substrates such as diphenyl ether, hydrogenolysis is followed by full hydrodeoxygenation producing the corresponding cycloalkanes as the main products. For unsymmetric substrates, the cleavage of the C-O bond is regioselective and occurs adjacent to the unsubstituted phenyl ring. As hydrogenation of benzene is faster than hydrodeoxygenation over the Ru@SILP-SO 3 H catalyst, controlled mixtures of cyclohexane and substituted phenols are accessible with good selectivity. Application of Ru@SILP-SO 3 H catalyst in continuous-flow hydrogenolysis of 2-methoxy-4-methylphenoxybenzene is demonstrated with use of commercial equipment.
- Rengshausen, Simon,Etscheidt, Fabian,Gro?kurth, Johannes,Luska, Kylie L.,Bordet, Alexis,Leitner, Walter
-
p. 405 - 412
(2019/02/26)
-
- Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
-
We herein report a simple and clean photo-induced metal-free reduction of C-X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C-I, C-Br and C-Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C-X H-O hydrogen bonding to decrease the activation energy.
- Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
-
supporting information
p. 767 - 770
(2019/01/21)
-
- Palladium(II) octaalkoxy- and octaphenoxyphthalocyanines: Synthesis and evaluation as catalysts in the Sonogashira reaction
-
Octaalkoxy- and octaphenoxysubstituted palladium phthalocyanines were used as a new family members of cross-coupling catalysts in the Sonogashira reaction. For the first time it was shown that terminal alkynes reacted mildly with p-substituted aryl bromides in gently conditions at room temperature under Pd and Cu-cocatalysis to give the corresponding phenylacetylenes. This protocol represents the use of palladium phthalocyanines as homogeneous catalysts in the Pd/Cu-promoted Sonogashira reaction.
- Platonova, Yana B.,Volov, Alexander N.,Tomilova, Larisa G.
-
p. 222 - 227
(2019/04/17)
-
- Base-promoted nucleophilic fluoroarenes substitution of C–F bonds
-
With the use of KOH/DMSO as the superbase medium, the nucleophilic fluoroarene substitution for C–F bonds is presented. The transformation proceeds smoothly with the use of fluoroarenes bearing not only electron-withdrawing group, but also electron-donating group and a variety of nucleophiles such as alcohols, phenols, amines, amides and nitrogen-heterocyclic compounds. The double nucleophilic substitution using ortho-difluoroarenes and nucleophiles bearing ortho-dinucleophilic groups results in the formation of 2,3-dihydro-1,4-benzodioxins, dibenzo[b,e][1,4]dioxins and 10H-phenoxazines in moderate to good yields.
- Su, Ji,Chen, Qian,Lu, Le,Ma, Yuan,Auyoung, George Hong Lok,Hua, Ruimao
-
supporting information
p. 303 - 307
(2017/12/11)
-
- Three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide for lignin model compound oxidation
-
A three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide (3D Co3O4/N-rGO) with a unique 3D porous structure was prepared, and its catalytic activity in lignin model compound oxidation was explored. The 3D Co3O4/N-rGO composite exhibits improved catalytic performance as compared to Co3O4 nanoparticles or 3D N-rGO in the oxidation of lignin model compounds. The higher catalytic activity of the 3D Co3O4/N-rGO composite is attributed to the combination of its porous structural features, large surface area that is provided by the 3D N-rGO matrix, and active Co3O4 nanoparticles doped on the N-rGO surface. The structural features of the 3D Co3O4/N-rGO are beneficial to reactant and product diffusion and transportation, and also are helpful in preventing aggregation of Co3O4 nanoparticles. In addition, the introduction of N atoms in rGO is also favorable for the formation of active oxygen species for the oxidation of model compounds. Given the high activity and the easy recovery from the reaction system, the 3D Co3O4/N-rGO composite should be applicable to non-noble metal catalytic systems for lignin model compounds.
- Zhang, Jiali,Zhang, Fangwei,Guo, Shouwu,Zhang, Jingyan
-
p. 11117 - 11123
(2018/07/05)
-
- Mechanistic studies of base-catalysed lignin depolymerisation in dimethyl carbonate
-
The depleting fossil reservoirs have stimulated global research initiatives on renewable lignin feedstocks as sustainable alternatives to petroleum-derived aromatics. Base-catalysed depolymerisation (BCD) is regarded as an economical and efficient approach for the valorisation of technical lignins. The major limiting factor encountered during this process is the re-condensation of the formed phenolic products, which results in lower monomer yields. To diminish these side reactions, we selected alkali earth metal catalysts in dimethyl carbonate (DMC) to produce methylated phenol derivatives as the final products. Herein, we demonstrate for the first time a base-promoted depolymerisation process affording low-molecular weight oils in high yields (52-67 wt%) wherein the employed bases are used in truly catalytic quantities (with catalyst loadings of around 5 mol%). The general applicability of this methodology was proved on four different lignin samples (1 Kraft, 3 organosolv) using caesium carbonate and lithium tert-butoxide as catalysts. The 2D NMR studies on the post-reaction lignin samples showed a similar degradation of the major lignin linkages for both bases. A difference in the reduction of phenolic moieties was revealed by quantitative 31P NMR analysis. Furthermore, GPC analysis demonstrated a significant shift towards lower mass fragments for the Cs2CO3-catalysed lignin degradation. A detailed GC-MS analysis for these samples identified a range of methoxy capped-monomeric degradation products. The scope of this reaction system was further expanded to lignocellulosic biomass such as milled beechwood chips, which notably showed similar product distributions. Based on the correlation of the experimental observations for extracted lignin samples and model compound studies, a mechanistic pathway for the Cs2CO3-catalysed system was suggested. DFT calculations provided reaction pathways for the observed cleavage products.
- Dabral, Saumya,Engel, Julien,Mottweiler, Jakob,Spoehrle, Stephanie S. M.,Lahive, Ciaran W.,Bolm, Carsten
-
p. 170 - 182
(2018/03/21)
-
- Rapid Iododeboronation with and without Gold Catalysis: Application to Radiolabelling of Arenes
-
Radiopharmaceuticals that incorporate radioactive iodine in combination with single-photon emission computed tomography imaging play a key role in nuclear medicine, with applications in drug development and disease diagnosis. Despite this importance, there are relatively few general methods for the incorporation of radioiodine into small molecules. This work reports a rapid air- and moisture-stable ipso-iododeboronation procedure that uses NIS in the non-toxic, green solvent dimethyl carbonate. The fast reaction and mild conditions of the gold-catalysed method led to the development of a highly efficient process for the radiolabelling of arenes, which constitutes the first example of an application of homogenous gold catalysis to selective radiosynthesis. This was exemplified by the efficient synthesis of radiolabelled meta-[125I]iodobenzylguanidine, a radiopharmaceutical that is used for the imaging and therapy of human norepinephrine transporter-expressing tumours.
- Webster, Stacey,O'Rourke, Kerry M.,Fletcher, Conor,Pimlott, Sally L.,Sutherland, Andrew,Lee, Ai-Lan
-
supporting information
p. 937 - 943
(2017/12/26)
-
- Efficient synthesis of α-substituted-α-arylmethyl phosphonates using trichloroacetimidate C–C coupling method
-
A simple convenient protocol for the synthesis of diethyl α,α-diaryl methylphosphonate derivatives 5a-f, 6b-f, 7a-f and 8a-f, diethyl α-alkenyl α-aryl methylphosphonates 9a-d and 10a-d and α-(oxoalkyl) α-aryl methylphosphonate 11a-d and 12a-d is described. Trichloroacetimidates 3a-d were treated with activated arenes, styrene, allyltrimethylsilane or silylenol ethers C-nucleophiles in the presence TMSOTf to afford the desired products in good yields and short reaction time.
- Fathalla, Walid,Pazdera, Pavel,El-Rayes, Samir,Ali, Ibrahim.A.I.
-
p. 1681 - 1691
(2018/03/01)
-
- Dimethomorph production method
-
The invention discloses a dimethomorph production method in the technical field of pesticide production. The production method comprises: 1) synthesizing veratrole; 2) synthesizing 3,4-dimethoxy-4-chloro-benzophenone; 3) synthesizing acetylmorpholine; and 4) synthesizing dimethomorph. Sodium tert-butoxide is taken as a basic catalyst for synthesizing dimethomorph from 3,4-dimethoxy-4-chloro-benzophenone and acetylmorpholine, and a sodium hydroxide solution is used to perform alkali washing on a reactant in a reaction vessel. Sodium hydroxide has a catalytic effect on synthesis of dimethomorphfrom 3,4-dimethoxy-4-chloro-benzophenone and acetylmorpholine. The defect that the catalytic effect of sodium tert-butoxide is gradually reduced due to unstable chemical property of sodium tert-butoxide and degradation of sodium tert-butoxide when sodium tert-butoxide comes into water is overcome. The dimethomorph product is improved in conversion rate and purity.
- -
-
Paragraph 0011; 0012; 0013
(2018/06/15)
-
- Green synthesis technology of rotundine sulfate
-
The invention provides a green synthesis technology of rotundine sulfate. The green synthesis technology comprises the following steps: firstly, taking pyrocatechol as a starting reactant, and carrying out esterification, acylation and nitration; then carrying out deoxygenation reduction to obtain 3,4-dimethoxyphenethylamine; then carrying out condensation on the obtained 3,4-dimethoxyphenethylamine and 2,3-dimethoxy benzaldehyde and reducing to obtain (3,4-dimethoxy)phenethyl(2,3-dimethoxy)benzylamine; finally, carrying out cyclization, reduction and sulfation on the obtained (3,4-dimethoxy)phenethyl(2,3-dimethoxy)benzylamine, so as to obtain finished-product rotundine sulfate. The invention develops a full-synthesis technology taking the pyrocatechol as a raw material, and provides an environment-friendly, low-cost and high-yield green synthesis technology for synthesizing the rotundine sulfate.
- -
-
Paragraph 0049; 0051; 0052; 0053; 0054
(2018/09/08)
-
- Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane
-
A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.
- Hokamp, Tobias,Dewanji, Abhishek,Lübbesmeyer, Maximilian,Mück-Lichtenfeld, Christian,Würthwein, Ernst-Ulrich,Studer, Armido
-
supporting information
p. 13275 - 13278
(2017/10/09)
-
- Preparing method for veratrole
-
The invention discloses a preparing method for veratrole. In the method, catechol and dimethyl carbonate are taken as raw materials and are subjected to reaction under a catalyst condition to produce veratrole. The method comprises the following specific progress: under the temperature condition of 0-5 DEG C, adding catechol and diethyl carbonate into a water solution, starting stirring and adding a catalyst, gradually heating to 100 DEG C, controlling the reaction system at a pH of 8-9 during reaction and then continuing to heat to reflux; after reflux is finished, performing standing and layering, adding liquid caustic soda into the oil phase, and performing washing, so as to obtain crude oil; and at last performing reduced-pressure distilling on the crude oil, so as to obtain a pure product veratrole. The catalyst is benzyltrimethylammonium chloride. The yield of veratrole prepared by the method is as high as 99% or more and the purity is as high as 99.5% or more. Furthermore, the whole manufacturing technique has the characteristics of low cost, environment friendliness and cleanness and safety.
- -
-
Paragraph 0015
(2017/05/18)
-
- Microwave-assisted methylation of dihydroxybenzene derivatives with dimethyl carbonate
-
Using a focused microwave reactor, methylation with dimethyl carbonate (DMC) of 1,2- and 1,4-dihydroxybenzene derivatives, found in the product spectrum of lignin depolymerisation, leads to the respective aromatic bis-methyl ethers with excellent isolated yields. Stoichiometric as well as catalytic amounts of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) are effective for the bis-methylation of these dihydroxybenzenes at relatively mild temperatures (160-190 °C). Conversion of resorcinol (1,3-dihydroxybenzene) under similar conditions leads to a mixture of 1,3-dimethoxybenzene and methyl 2,4-dimethoxybenzoate. The unusual reactivity of resorcinol's phenyl ring towards DMC can be explained by the synergic effect of its two strongly activating ortho/para directing groups.
- Lui, Matthew Y.,Lokare, Kapil S.,Hemming, Ellen,Stanley, Jessica N.G.,Perosa, Alvise,Selva, Maurizio,Masters, Anthony F.,Maschmeyer, Thomas
-
p. 58443 - 58451
(2016/07/06)
-
- Dual gold photoredox C(sp2)-C(sp2) cross couplings-development and mechanistic studies
-
A dual visible light photoredox and gold-catalysed C(sp2)-C(sp2) cross coupling is described. The success of this mild, oxidant- and base-free cross coupling is highly dependent on the amount of water added. Mechanistic studies show two distinct pathways depending on the gold catalyst employed: transmetallation of the arylboronic acid with gold(i) occurs prior to oxidation of gold(i) to gold(iii) using cationic gold(i) catalysts, whereas oxidation of gold(i) to gold(iii) precedes transmetallation using neutral gold(i) catalysts.
- Gauchot, Vincent,Lee, Ai-Lan
-
supporting information
p. 10163 - 10166
(2016/08/18)
-
- Radical Hydrodeiodination of Aryl, Alkenyl, Alkynyl, and Alkyl Iodides with an Alcoholate as Organic Chain Reductant through Electron Catalysis
-
A simple and efficient method for radical hydrodeiodination is reported. The novel approach uses electron catalysis. In situ generated Na-alcoholates are introduced as radical chain reducing reagents and reactions work with O2as cheap initiator. Hydrodeiodination works on aryl, alkenyl, alkynyl iodides and a tert-alkyl iodide also gets reduced applying the method. Albeit less general, the method is also applicable to the reduction of aryl bromides. The novel reagent is successfully used to conduct typical reductive radical cyclization reactions and mechanistic studies are reported.
- Dewanji, Abhishek,Mück-Lichtenfeld, Christian,Studer, Armido
-
supporting information
p. 6749 - 6752
(2016/06/09)
-
- Mapping reactivities of aromatic models with a lignin disassembly catalyst. Steps toward controlling product selectivity
-
Copper-doped porous metal oxides catalyze the one-pot disassembly of biomass-derived lignin via C-O bond hydrogenolysis and hydrodeoxygenation in supercritical methanol. This catalytic system cleanly converts lignin as well as lignocellulose composites, such as sawdust, to organic liquids with little or no formation of intractable tars or chars. However, this catalyst based on Earth-abundant components also catalyzes less desirable aromatic ring hydrogenations and various methylations that contribute to the diversity of products. In this context, we undertook a quantitative experimental and computational evaluation of model reactions relevant to the reductive disassembly of lignin by this catalyst system in order to determine quantitatively the rates of desirable and less desirable chemical steps that define the overall product selectivities. Global fitting analysis methods were used to map the temporal evolution of key intermediates and products and to elucidate networks that provide guidelines regarding the eventual fates of reactive intermediates in this catalysis system. Phenolic compounds display multiple reaction pathways, but substrates such as benzene, toluene, and alkyl- and alkoxy-substituted aromatics are considerably more stable under these conditions. These results indicate that modifying this catalytic system in a way that controls and channels the reactivity of phenolic intermediates should improve selectivity toward producing valuable aromatic chemicals from biomass-derived lignin. To this end we demonstrate that the O-methylating agent dimethyl carbonate can intercept the phenol intermediate formed from hydrogenolysis of the model compound benzyl phenyl ether. Trapping the phenol as anisole thus gave much higher selectivity towards aromatic products.
- Bernt, Christopher M.,Bottari, Giovanni,Barrett, Jacob A.,Scott, Susannah L.,Barta, Katalin,Ford, Peter C.
-
p. 2984 - 2994
(2016/05/24)
-
- Masked N-Heterocyclic Carbene-Catalyzed Alkylation of Phenols with Organic Carbonates
-
An easily prepared masked N-heterocyclic carbene, 1,3-dimethylimidazolium-2-carboxylate (DMI-CO2), was investigated as a “green” and inexpensive organocatalyst for the alkylation of phenols. The process made use of various low-toxicity and renewable alkylating agents, such as dimethyl- and diethyl carbonate, in a focused microwave reactor. DMI-CO2 was found to be a very active catalyst and excellent yields of a range of aryl alkyl ethers were obtained under relatively benign conditions. The observed difference in the conversion behavior of phenol methylation, in the presence of either the carbene or 1,8-diazabicycloundec-7-ene (DBU) catalyst, was rationalized on the basis of mechanistic investigations. The primary mode of action for the N-heterocyclic carbene is nucleophilic catalysis. Activation of the dialkyl carbonate electrophile results in concomitant evolution of an organo-soluble alkoxide, which deprotonates the phenolic starting material. In contrast, DBU is initially protonated by the phenol and thus consumed. Subsequent regeneration and participation in nucleophilic catalysis only becomes significant after some phenolate alkylation occurs.
- Lui, Matthew Y.,Yuen, Alexander K. L.,Masters, Anthony F.,Maschmeyer, Thomas
-
p. 2312 - 2316
(2016/10/24)
-
- Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy to Assemble Them into Solid State Materials with a π-π Stacked Lamellar Structure
-
Formation of π-π stacked lamellar structure is important for high performance organic semiconductor materials. We previously demonstrated that perfluoroalkylation of aromatics and heteroaromatics was one of the strategies to design organic crystalline materials with π-π stacked lamellar structures while improving air stability as a result of the strong electron withdrawing ability of perfluoroalkyl substituents. Square-planar transition metal complexes with large π-conjugated ligands are also an important category of semiconductor materials. We have perfluoroalkylated square-planar transition metal complexes, leading to the formation of a π-π stacked lamellar crystal packing motif in the solid state. Here we report six crystal structures of Pd and Pt complexes with bis-perfluorobutylated catechol ligand as one of the two ligands that bonds to the metal centers. This structural design possesses similar molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we have reported previously, again, demonstrating the steering power of the perfluoroalkyl substituents in engineering organic and organometallic solid state materials.
- Banikhaled, Mohammad O.,Becker, John D.,Koppang, Miles,Sun, Haoran
-
p. 1869 - 1878
(2016/05/09)
-
- Palladium Nanoparticles Supported on Fibrous Silica (KCC-1-PEI/Pd): A Sustainable Nanocatalyst for Decarbonylation Reactions
-
A practical and convenient decarbonylation of a variety of aromatic, heteroaromatic, and alkenyl aldehydes by using palladium nanoparticles supported on novel, fibrous nanosilica, named KCC-1-PEI/Pd, has been developed. Complete conversion of aldehyde functionalities into deformylated products was achieved in all cases and in nearly all cycles tested by reusing the catalyst systems. This method eliminates further purification of products after their isolation. Syntheses of at least three different deformylated products have been shown in sequence with the same catalyst system, which neither requires use of any additives, such as oxidants and bases, nor CO scavengers.
- Kundu, Pintu K.,Dhiman, Mahak,Modak, Atanu,Chowdhury, Arindam,Polshettiwar, Vivek,Maiti, Debabrata
-
p. 1142 - 1146
(2016/11/23)
-
- Shifting Chemical Equilibria in Flow - Efficient Decarbonylation Driven by Annular Flow Regimes
-
To efficiently drive chemical reactions, it is often necessary to influence an equilibrium by removing one or more components from the reaction space. Such manipulation is straightforward in open systems, for example, by distillation of a volatile product from the reaction mixture. Herein we describe a unique high-temperature/high-pressure gas/liquid continuous-flow process for the rhodium-catalyzed decarbonylation of aldehydes. The carbon monoxide released during the reaction is carried with a stream of an inert gas through the center of the tubing, whereas the liquid feed travels as an annular film along the wall of the channel. As a consequence, carbon monoxide is effectively vaporized from the liquid phase into the gas phase and stripped from the reaction mixture, thus driving the equilibrium to the product and preventing poisoning of the catalyst. This approach enables the catalytic decarbonylation of a variety of aldehydes with unprecedented efficiency with a standard coil-based flow device.
- Gutmann, Bernhard,Elsner, Petteri,Glasnov, Toma,Roberge, Dominique M.,Kappe, C. Oliver
-
supporting information
p. 11557 - 11561
(2016/02/19)
-
- Base-catalysed cleavage of lignin β-O-4 model compounds in dimethyl carbonate
-
A base-catalysed transformation and cleavage of lignin β-O-4 model compounds in dimethyl carbonate is reported. The reaction system consists of readily available bases and inexpensive dimethyl carbonate as a solvent and reagent, affording methoxy benzene or 2-aryloxyvinyl benzene derivatives in good to very good yields. The applicability of the system for the bond cleavage in an organosolv lignin sample was demonstrated.
- Dabral, Saumya,Mottweiler, Jakob,Rinesch, Torsten,Bolm, CarstenU
-
p. 4908 - 4912
(2015/11/11)
-
- Method for producing alkoxy-hydroxybenzaldehyde that is substantially free of alkyl-alkoxy-hydroxybenzaldehyde
-
The invention relates to a method for producing at least one alkoxy-hydroxybenzaldehyde (AHBA) from at least one hydroxyphenol (HP), said method being characterised in that it comprises the formation of at least one alkoxyphenol (AP) and alkyl-alkoxyphenol (AAP) and the separation (S) of AP from AAP, said separation (S) being carried out prior to obtaining AHBA.
- -
-
Paragraph 0265-0313
(2015/07/27)
-
- ALKYLATION OF PHENOLIC COMPOUNDS
-
The invention relates to a process for O-alkyiation of a phenolic compound comprising at least two hydroxyl groups bonded to an aromatic hydrocarbon, the process comprising reacting the phenolic compound with an alkylating agent in the presence of a base, at a suitable reaction temperature and for a suitable time period, thereby alkylating the at least two hydroxy] groups. The invention also relates to O-alkylaled phenolic compounds produced by this process.
- -
-
Page/Page column 39
(2015/04/28)
-
- Gold-Catalyzed Proto- and Deuterodeboronation
-
A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.
- Barker, Graeme,Webster, Stacey,Johnson, David G.,Curley, Rachel,Andrews, Matthew,Young, Paul C.,MacGregor, Stuart A.,Lee, Ai-Lan
-
p. 9807 - 9816
(2015/11/03)
-
- Ruthenium-Catalyzed C-C bond cleavage in lignin model substrates
-
Ruthenium-triphos complexes exhibited unprecedented catalytic activity and selectivity in the redox-neutral C-C bond cleavage of the β-O-4 lignin linkage of 1,3-dilignol model compounds. A mechanistic pathway involving a dehydrogenation-initiated retro-aldol reaction for the C-C bond cleavage was proposed in line with experimental data and DFT calculations.
- Vom Stein, Thorsten,Den Hartog, Tim,Buendia, Julien,Stoychev, Spas,Mottweiler, Jakob,Bolm, Carsten,Klankermayer, Jürgen,Leitner, Walter
-
supporting information
p. 5859 - 5863
(2015/05/13)
-
- Influences of Various Supports, γ-Al2O3, CeO2, and SBA-15 on HDO Performance of NiMo Catalyst
-
Hydrodeoxygenation (HDO) of guaiacol (GUA), has been carried out over γ-Al2O3, CeO2, SBA-15 supported NiMo catalysts in an autoclave at 250°C and a hydrogen pressure of 5 MPa. In comparison with NiMo/γ-Al2O3, both NiMo/CeO2 and NiMo/SBA-15 catalysts showed their higher activities. NiMo/SBA-15 has been found to be the most potential one for HDO of GUA with GUA conversion and HDO degree of 90 and 67.5 %, respectively. The main product was cyclohexane with its yield of 56 mol%. The outstanding activity of this catalyst results from a high dispersion of its active sites on SBA-15 as catalyst support. For CeO2 supported catalyst, some interactions of Ce-Mo can be occurred, leading to an enhancement of its HDO performance. Graphical Abstract: [Figure not available: see fulltext.]
- Phan, Binh M. Q.,Ha, Quan L. M.,Le, Nguyen P.,Ngo, Phuong T.,Nguyen, Thu H.,Dang, Tung T.,Nguyen, Luong H.,Nguyen, Duc A.,Luu, Loc C.
-
p. 662 - 669
(2015/08/04)
-
- Selective O-methylation of phenols and benzyl alcohols in simple pyridinium based ionic liquids
-
Synthesis of pyridinium based ionic liquids were reported and applied as catalyst for the selective O-methylation of phenols and benzyl alcohols. The reactions were carried out by using dimethylcarbonate (DMC) as the methylating agent. High selectivity, high yield and recyclability of the ionic liquids are important features of the reactions.
- Das, Pranab Jyoti,Das, Jupitara
-
-
- Metal-free protodeboronation of electron-rich arene boronic acids and its application to ortho -functionalization of electron-rich arenes using a boronic acid as a blocking group
-
The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided. On the basis of this protodeboronation, a new protocol for the synthesis of ortho-functionalized electron-rich arenes from these boronic acids was developed using the boronic acid moiety as a blocking group in the electrophilic aromatic substitution reaction, followed by the removal of the boronic acid moiety via thermal protodeboronation. Mechanistic studies suggested that this protodeboronation might proceed via the complex formation of a boronic acid with a proton source, followed by the carbon-boron bond fission through σ-bond metathesis, to afford the corresponding arene compound and boric acid.
- Ahn, Su-Jin,Lee, Chun-Young,Kim, Nak-Kyoon,Cheon, Cheol-Hong
-
p. 7277 - 7285
(2014/11/27)
-
- New synthesis of (±)-cherylline and mono- and dimethyl ethers
-
The synthesis of 4-aryl-1,2,3,4-tetrahydroisoquinolines is achieved via the ether rearrangement methodology. Subsequent reactions yielded cherylline and ether derivatives of amaryllidaceac alkaloids. Copyright
- Pailla, Uma Reddy,Arava, Veera Reddy,Ravindhranath
-
p. 2232 - 2238
(2014/07/07)
-
- Effect of support modifications for CoMo/γ-Al2O 3 and CoMo/ASA catalysts in the hydrodeoxygenation of guaiacol
-
CoMo catalysts supported on a commercial alumina (γ-Al 2O3) modified with Na (1, 2 and 3 wt.%) and supported on amorphous aluminosilicates (ASA) with different Si/(Si + Al) ratios (0.15, 0.25 and 0.75) were prepared. Additionally, a CoMo catalyst supported on ASA modified with 3 wt.% Na was synthetized. These catalysts were evaluated in the hydrodeoxygenation (HDO) of guaiacol (2-methoxyphenol) as bio-oil model compound. The results show a decrease of catalytic activity with increasing amounts of Na added compared to an unmodified catalyst. This modification in the acid-base properties of the catalyst generates changes in selectivity such as the inhibition of methylated compounds formation, e.g., cresol and the increase of phenol production. For ASA-supported catalysts, a decrease in catalytic activity with the increase in the Si content took place, whereas the HDO degree was not significantly affected. Moreover, the ASA-supported catalysts led to a lower activity of the HDO of guaiacol compared to γ-Al2O 3-supported catalysts.
- Mora, Iván D.,Méndez, Edna,Duarte, Liseth J.,Giraldo, Sonia A.
-
-
- Hydrodeoxygenation of guaiacol over carbon-supported metal catalysts
-
Catalytic bio-oil upgrading to produce renewable fuels has attracted increasing attention in response to the decreasing oil reserves and the increased fuel demand worldwide. Herein, the catalytic hydrodeoxygenation (HDO) of guaiacol with carbon-supported non-sulfided metal catalysts was investigated. Catalytic tests were performed at 4.0MPa and temperatures ranging from 623 to 673K. Both Ru/C and Mo/C catalysts showed promising catalytic performance in HDO. The selectivity to benzene was 69.5 and 83.5% at 653K over Ru/C and 10Mo/C catalysts, respectively. Phenol, with a selectivity as high as 76.5%, was observed mainly on 1Mo/C. However, the reaction pathway over both catalysts is different. Over the Ru/C catalyst, the O-CH3 bond was cleaved to form the primary intermediate catechol, whereas only traces of catechol were detected over Mo/C catalysts. In addition, two types of active sites were detected over Mo samples after reduction in H2 at 973K. Catalytic studies showed that the demethoxylation of guaiacol is performed over residual MoOx sites with high selectivity to phenol whereas the consecutive HDO of phenol is performed over molybdenum carbide species, which is widely available only on the 10Mo/C sample. Different deactivation patterns were also observed over Ru/C and Mo/C catalysts.
- Chang, Jie,Danuthai, Tanate,Dewiyanti, Silvia,Wang, Chuan,Borgna, Armando
-
p. 3041 - 3049
(2013/10/21)
-
- Synthesis of aryl ethers from aromatic carboxylic acids
-
A silver/copper bimetallic catalyst system promotes the decarboxylative Chan-Evans-Lam alkoxylation of ortho-substituted aromatic carboxylate salts with tetraalkyl orthosilicates or triaryl borates. Non-ortho-substituted carboxylates are alkoxylated via an ortho-C-H-alkoxylation with concomitant cleavage of the carboxylate directing group via protodecarboxylation. This way, meta-substituted carboxylates are converted into para-substituted alkoxyarenes and vice versa. The combined processes provide a convenient synthetic entry to the important class of aromatic ethers from widely available carboxylic acids.
- Bhadra, Sukalyan,Dzik, Wojciech I.,Goossen, Lukas J.
-
supporting information
p. 2387 - 2390
(2013/09/23)
-
- Heterogeneous palladium catalysts for decarbonylation of biomass-derived molecules under mild conditions
-
Workin′ 6 to 5: A highly active heterogeneous catalyst, Pd/SBA-15(DP), promotes the selective decarbonylation of biomass-derived HMF to furfural alcohol with a high yield, up to 96 %, in mild conditions. The route offers a simple and effective method of linking C6 and C5 molecules in the biomass conversion value chain. In addition to HMF the catalyst is effective towards the decarbonylation of other biomass-derived aldehydes, also. Copyright
- Huang, Yao-Bing,Yang, Zhen,Chen, Meng-Yuan,Dai, Jian-Jun,Guo, Qing-Xiang,Fu, Yao
-
p. 1348 - 1351
(2013/09/12)
-
- Liquid crystalline bis(N-salicylideneaniline)s: Synthesis and thermal behavior of constitutional isomers
-
The first examples of mesogenic bis(N-salicylideneaniline)s (BSANs), wherein two lipophilic (half-disk shaped) entities are interlinked through the dihydroxydiformylbenzene core, were synthesized and characterized. In particular, three constitutional (positional) isomeric BSANs were prepared by the facile twofold condensation of 3,4,5-tris(alkoxy)anilines with 2,3-dihydroxyterephthalaldehyde, 4,6-dihydroxyisophthalaldehyde, and 2,5-dihydroxyterephthalaldehyde and their structures were established by elemental analyses, FT-IR, 1H NMR, and 13C NMR. Proton NMR experiments demonstrated their existence in enol-imine (OH) form solely. Polarizing optical microscopic, differential scanning calorimetric, and powder X-ray diffraction studies evidenced the occurrence of columnar mesomorphism in two sets of isomers.
- Hiremath, Uma S.
-
p. 3419 - 3423
(2013/07/04)
-