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Designer Outer Membrane Protein Facilitates Uptake of Decoy Molecules into a Cytochrome P450BM3-Based Whole-Cell Biocatalyst
We report an OmpF loop deletion mutant, which improves the cellular uptake of external additives into an Escherichia coli whole-cell biocatalyst. Through co-expression of the OmpF mutant with wild-type P450BM3 in the presence of decoy molecules, the yield
Karasawa, Masayuki,Shoji, Osami,Stanfield, Joshua Kyle,Suzuki, Kazuto,Yonemura, Kai
supporting information

(2021/12/16)

Increasing the steric hindrance around the catalytic core of a self-assembled imine-based non-heme iron catalyst for C-H oxidation
Sterically hindered imine-based non-heme complexes4and5rapidly self-assemble in acetonitrile at 25 °C, when the corresponding building blocks are added in solution in the proper ratios. Such complexes are investigated as catalysts for the H2O2oxidation of a series of substrates in order to ascertain the role and the importance of the ligand steric hindrance on the action of the catalytic core1, previously shown to be an efficient catalyst for aliphatic and aromatic C-H bond oxidation. The study reveals a modest dependence of the output of the oxidation reactions on the presence of bulky substituents in the backbone of the catalyst, both in terms of activity and selectivity. This result supports a previously hypothesized catalytic mechanism, which is based on the hemi-lability of the metal complex. In the active form of the catalyst, one of the pyridine arms temporarily leaves the iron centre, freeing up a lot of room for the access of the substrate.
Frateloreto, Federico,Capocasa, Giorgio,Olivo, Giorgio,Abdel Hady, Karim,Sappino, Carla,Di Berto Mancini, Marika,Levi Mortera, Stefano,Lanzalunga, Osvaldo,Di Stefano, Stefano
p. 537 - 542
(2021/02/09)

Insight into the chemoselective aromatic: Vs. side-chain hydroxylation of alkylaromatics with H2O2catalyzed by a non-heme imine-based iron complex
The oxidation of a series of alkylaromatic compounds with H2O2 catalyzed by an imine-based non-heme iron complex prepared in situ by reaction of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2?:?2?:?1 ratio leads to a marked chemoselectivity for aromatic ring hydroxylation over side-chain oxidation. This selectivity is herein investigated in detail. Side-chain/ring oxygenated product ratio was found to increase upon decreasing the bond dissociation energy (BDE) of the benzylic C-H bond in line with expectation. Evidence for competitive reactions leading either to aromatic hydroxylation via electrophilic aromatic substitution or side-chain oxidation via benzylic hydrogen atom abstraction, promoted by a metal-based oxidant, has been provided by kinetic isotope effect analysis. This journal is
Ticconi, Barbara,Capocasa, Giorgio,Cerrato, Andrea,Di Stefano, Stefano,Lapi, Andrea,Marincioni, Beatrice,Olivo, Giorgio,Lanzalunga, Osvaldo
p. 171 - 178
(2021/01/28)

Preparation of NiCu Alloy Catalyst for the Hydrodeoxygenation of Benzofuran
A series of bimetallic NixCu(10-x)/SiO2 (where x is the mass fraction of Ni and the total metal loading was fixed at 10 wt%.) catalysts with different Ni/Cu mass ratio are prepared and characterized by X-Ray diffraction (XRD), N2 adsorption-desorption, inductively coupled plasma mass spectrometry (ICP-MS), H2 temperature-programmed reduction (H2-TPR) and transmission electron microscope (TEM). The benzofuran (BF) hydrodeoxygenation (HDO) performance of as-prepared catalysts are evaluated in a fixed flow reactor. The results showed that the incorporation of Cu to Ni/SiO2 catalyst can increase surface area of catalyst and improve the reducibility of nickel oxide species, which contributed to higher catalytic activity and total deoxygenated compounds yield. Moreover, the strong synergistic effect between Ni and Cu led to the formation of NiCu alloy at the Ni mass fraction of 5 wt% and thus induced smaller crystallite size and exposure of more active particles, which inevitably contributed to the improved HDO performance for Ni5Cu5/SiO2 catalyst. At 300 °C, 3.0 MPa, MHSV=3.0 h?1 and H2/oil = 500(v/v), the total yield of deoxygenated products over Ni5Cu5/SiO2 catalyst reached 86.0%, which is increased by 10.8% and 77.4% as compared to those of monometallic Ni/SiO2 (75.2%) and Cu/SiO2 catalysts (8.8%), respectively. Finally, a possible reaction network for HDO of BF on Ni5Cu5/SiO2 catalyst was proposed. Graphic Abstract: [Figure not available: see fulltext.]
Zhu, Tianhan,Song, Hua,Li, Feng,Chen, Yanguang
p. 1670 - 1682
(2020/10/21)

Aromatic C?H Hydroxylation Reactions with Hydrogen Peroxide Catalyzed by Bulky Manganese Complexes
The oxidation of aromatic substrates to phenols with H2O2 as a benign oxidant remains an ongoing challenge in synthetic chemistry. Herein, we successfully achieved to catalyze aromatic C?H bond oxidations using a series of biologically inspired manganese catalysts in fluorinated alcohol solvents. While introduction of bulky substituents into the ligand structure of the catalyst favors aromatic C?H oxidations in alkylbenzenes, oxidation occurs at the benzylic position with ligands bearing electron-rich substituents. Therefore, the nature of the ligand is key in controlling the chemoselectivity of these Mn-catalyzed C?H oxidations. We show that introduction of bulky groups into the ligand prevents catalyst inhibition through phenolate-binding, consequently providing higher catalytic turnover numbers for phenol formation. Furthermore, employing halogenated carboxylic acids in the presence of bulky catalysts provides enhanced catalytic activities, which can be attributed to their low pKa values that reduces catalyst inhibition by phenolate protonation as well as to their electron-withdrawing character that makes the manganese oxo species a more electrophilic oxidant. Moreover, to the best of our knowledge, the new system can accomplish the oxidation of alkylbenzenes with the highest yields so far reported for homogeneous arene hydroxylation catalysts. Overall our data provide a proof-of-concept of how Mn(II)/H2O2/RCO2H oxidation systems are easily tunable by means of the solvent, carboxylic acid additive, and steric demand of the ligand. The chemo- and site-selectivity patterns of the current system, a negligible KIE, the observation of an NIH-shift, and the effectiveness of using tBuOOH as oxidant overall suggest that hydroxylation of aromatic C?H bonds proceeds through a metal-based mechanism, with no significant involvement of hydroxyl radicals, and via an arene oxide intermediate. (Figure presented.).
Masferrer-Rius, Eduard,Borrell, Margarida,Lutz, Martin,Costas, Miquel,Klein Gebbink, Robertus J. M.
p. 3783 - 3795
(2021/03/09)

A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh2andtBuOK
A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2andtBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.
Pan, Wenjing,Li, Chenchen,Zhu, Haoyin,Li, Fangfang,Li, Tao,Zhao, Wanxiang
p. 7633 - 7640
(2021/09/22)

CATALYTIC FUNNELING OF PHENOLICS
In general, present invention concerns an integrated wood-to-xylochemicals biorefinery, enabling production of renewable phenol, phenolic oligomers, propylene, and carbohydrate pulp from lignocellulosic biomass.
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Paragraph 0035; 0089-0090; 0169

(2021/04/30)

Preparation method of alkyl aromatic compound based on alkenyl ether Friedel-Crafts reaction
The invention discloses a preparation method of an alkyl aromatic compound based on an alkenyl ether Friedel-Crafts reaction, and belongs to the technical field of pharmaceutical and chemical intermediates and related chemistry. According to the method, alkenyl ether and an aromatic compound are used as raw materials, and green and efficient synthesis of the alkyl-substituted aromatic compound isrealized under the catalytic action of Lewis acid or protonic acid. The method has the advantages of high selectivity, mild reaction conditions, good functional group compatibility, the wide substraterange, environmental friendliness and the like. The alkyl-substituted aromatic compound is an important organic synthesis intermediate and has very wide application in the fields of organic synthesisand pharmacy, so that the alkyl-substituted aromatic compound has relatively high application value and social and economic benefits.
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Paragraph 0055-0057

(2020/07/24)

Synthesis of Highly Substituted Phenols and Benzenes with Complete Regiochemical Control
Substituted phenols are requisite molecules for human health, agriculture, and diverse synthetic materials. We report a chemical synthesis of phenols, including penta-substituted phenols, that accommodates programmable substitution at any position. This method uses a one-step conversion of readily available hydroxypyrone and nitroalkene starting materials to give phenols with complete regiochemical control and in high chemical yield. Additionally, the phenols can be converted into highly and even fully substituted benzenes.
Zhang, Xiaojie,Beaudry, Christopher M.
supporting information
p. 6086 - 6090
(2020/08/12)

Synthesis of Ni2P/Al2O3 utilizing triphenylphosphine (TPP) as the phosphorus source for hydrodeoxygenation of benzofuran
A novel route to synthesize highly active Ni2P/Al2O3 (TPP) utilizing triphenylphosphine (TPP) as the phosphorus source at a low temperature of 573 K is described. The as-prepared catalysts were characterized by X-ray diffraction (XRD), CO uptake, Brunner-Emmett-Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the Ni2P/Al2O3 (TPP) catalyst and the role of the TPP phosphorus source were studied using hydrodeoxygenation (HDO) of benzofuran (BF) as a probe reaction. The results show that the use of TPP as the phosphorus source could suppress the strong interaction between phosphate and Al2O3, thereby the formation of AlPO4 was avoided. As compared to the Ni2P/Al2O3 prepared by using (NH4)2HPO4 as the phosphorus source, Ni2P/Al2O3 (TPP) possessed significantly higher surface area and smaller Ni2P particle size. The HDO activity and yield of O-free products over the Ni2P/Al2O3 (TPP) catalyst were increased by 17.2% and 36.0%, respectively, when compared with those found for Ni2P/Al2O3 prepared using (NH4)2HPO4. The use of TPP as the phosphorus source could effectively promote the dehydration of 2-ethylphenol (2-EtPh) to form ethylbenzene (EB), and the demethylation of ethylcyclohexane (ECH) to methylcyclohexane (MCH).
Jiang, Bolong,Jiang, Nan,Han, Chunbao
p. 7577 - 7582
(2020/06/19)

Palladium-catalyzed aerobic synthesis of: Ortho -substituted phenols from cyclohexanones and primary alcohols
Due to the importance of phenols as structural cores and precursors of chemical products, synthesis of site-specific substituted phenols is highly desirable and a significant challenge. An aerobic palladium-catalyzed site-specific synthesis of ortho-substituted phenols from cyclohexanones and primary alcohols via an oxidation/aldol/dehydration/aromatization process has been developed. Various substituted cyclohexanones and primary alcohols are successfully transformed into ortho-substituted phenols. In addition, this catalytic reaction uses air as the terminal oxidant and generates water as the sole by-product. Furthermore, the method can also be extended to polyhydroxyl substituted substrates with high chemoselectivity between primary and secondary alcohols. This method provides a greener tool for synthesizing primary alkyl ortho-substituted phenols.
Zeng, Huiying,Yu, Jianjin,Li, Chao-Jun
supporting information
p. 1239 - 1242
(2020/02/04)

Guaiacol demethoxylation catalyzed by Re2O7 in ethanol
Re2O7 is used to convert guaiacol in alcohols at 280–320 °C. In ethanol, guaiacol is deoxygenated and alkylated, and the major products are phenol and alkylphenols (including ethylphenol, diethylphenol, diisopropylphenol, di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol), accounting for 97 mol% of all products after 6 hour reaction at 320 °C. Both catechol and phenol are the intermediates of guaiacol demethoxylation. Among the substituents, ethyl is directly provided by ethanol while isopropyl and tert-butyl are formed by the addition of methyl to ethyl step by step. In addition, Re2O7 has negligible activity for the saturation of benzene ring so it does not cause considerable over-consumption of reductant. The actual catalyst for guaiacol demethoxylation is likely a ReIV?VI species.
Yan, Fei,Sang, Yushuai,Bai, Yunfei,Wu, Kai,Cui, Kai,Wen, Zhe,Mai, Fuhang,Ma, Zewei,Yu, Linhao,Chen, Hong,Li, Yongdan
p. 231 - 237
(2019/08/12)

Recyclable Pd/C catalyzed one-step reduction of carbonyls to hydrocarbons under simple conditions without extra base
The reductions of carbonyls for the synthesis of hydrocarbons were developed with hydrazine hydrate, hydrogen gas and ammonium formate respectively. The simple, mild and efficient conditions were provided by employing recyclable Pd/C as catalyst in normal solvents at 100 °C and the reactions proceeded smoothly to produce the corresponding products with good to excellent yields. And gram-scale reactions and recycling of the catalyst were also demonstrated. Furtherly, the mechanism has been proposed.
Zhou, Xiao-Yu,Chen, Xia
supporting information

(2019/12/06)

Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu?SILP catalyst
The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75?SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts. This journal is
Bordet, Alexis,Goclik, Lisa,Leitner, Walter,Offner-Marko, Lisa
supporting information
p. 9509 - 9512
(2020/09/02)

Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach
A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96percent. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.
Bartolomeu, Aloisio De A.,Brocksom, Timothy J.,De Oliveira, Kleber T.,No?l, Timothy,Silva, Rodrigo C.
(2019/08/26)

Polymer-supported eosin Y as a reusable photocatalyst for visible light mediated organic transformations
A novel polymer-supported recyclable photocatalyst has been developed for visible light mediated oxidation reactions. The organic dye eosin Y was loaded on macroporous commercially available Amberlite IRA 900 chloride resin and exploited as a photocatalyst for visible light mediated oxidation of thioethers to sulfoxides and phenylboronic acids to phenols under open atmospheric air. Varieties of functional groups were well tolerated during oxidation. The catalyst is recyclable for six cycles without significant loss in its efficiency. Furthermore, gram-scale oxidation of sulfides to sulfoxides has been demonstrated to prove the commercial viability of the method.
Sridhar, Arunasalam,Rangasamy, Rajmohan,Selvaraj, Mari
p. 17974 - 17979
(2019/12/02)

Ru/hydroxyapatite as a dual-functional catalyst for efficient transfer hydrogenolytic cleavage of aromatic ether bonds without additional bases
Cleavage of aromatic ether bonds is a key step for lignin valorization, and the development of novel heterogeneous catalysts with high activity is crucial. Herein, bifunctional Ru/hydroxyapatite has been prepared via ion exchange and subsequent reduction. The obtained Ru/hydroxyapatite could efficiently catalyze the cleavage of various compounds containing aromatic ether bonds via transfer hydrogenolysis without additional bases. Systematic studies indicated that the basic nature of hydroxyapatite and electron-enriched Ru sites resulted in the high activity of the catalyst. A mechanism study revealed that the direct cleavage of aromatic ether bonds was the main reaction pathway.
Hua, Manli,Song, Jinliang,Xie, Chao,Wu, Haoran,Hu, Yue,Huang, Xin,Han, Buxing
supporting information
p. 5073 - 5079
(2019/09/30)

Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
Matt, Christof,K?lblin, Frederic,Streuff, Jan
supporting information
p. 6983 - 6988
(2019/09/09)

Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
p. 220 - 226
(2019/01/05)

Effect of preparation temperature on the structures and hydrodeoxygenation performance of Ni2P/C catalysts prepared by decomposition of hypophosphites
A novel method for preparing Ni2P/C-x (x = preparation temperature, °C) catalysts in a flowing N2 atmosphere by decomposition of hypophosphites was proposed, and the effect of preparation temperature on the hydrodeoxygenation performance of the catalysts was further investigated. X-ray diffraction (XRD), N2-adsorption specific surface area measurements, CO uptake, and X-ray photoelectron spectroscopy (XPS) were applied. The performances of the Ni2P/C-x catalysts prepared at different preparation temperatures were tested in the benzofuran hydrodeoxygenation (BF HDO) reaction. The diffraction peaks related to Ni2P can be seen when x ≧ 400 °C. With increasing x, the Ni2P crystallite size and CO uptake amount of the Ni2P/C-x catalysts increased, and the amount of phosphorous decreased. The BF conversion and yield of total O-free products over the Ni2P/C-x catalysts increased with increasing preparation temperature. The Ni2P/C-550 catalyst showed a BF HDO conversion of 91.6% and a yield of total O-free products of 70.2% under the reaction conditions of 300 °C, 3.0 MPa, a H2/oil ratio of 500 (V/V), and a weight hourly space velocity (WHSV) of 4.0 h?1.
Dai, Xueya,Song, Hua,Yan, Zijin,Li, Feng,Chen, Yanguang,Wang, Xueqin,Yuan, Dandan,Zhang, Jiaojing,Wang, Yuanyuan
p. 19917 - 19923
(2018/12/13)

Method for preparing hydrocarbyl phenol by catalytic conversion of phenolic compound in presence of molybdenum-based catalyst
The invention discloses a method for preparing hydrocarbyl phenol by catalytic conversion of a phenolic compound in the presence of a molybdenum-based catalyst. The method comprises mixing a phenoliccompound, a molybdenum-based catalyst and a reaction solvent, adding the mixture into a sealed reactor, feeding gas into the reactor, heating the mixture to 150-350 DEG C, carrying out stirring for areaction for 0.5-2h, then filtering to remove a solid catalyst and carrying out rotary evaporateion to obtain a liquid product. The phenolic compound has a wide source, a cost is low, product alkyl phenol selectivity is high, an added value is high, alcohol or an alcohol-water mixture is used as a reaction solvent, environmental friendliness is realized, pollution is avoided, any inorganic acids and alkalis are avoided in the reaction process, the common environmental pollution problems in the biomass processing technology are solved, the reaction conditions are mild, the process can be carried out at a low temperature, high-efficiency conversion of the reactants can be realized without consuming hydrogen gas and the method is suitable for large-scale industrial trial production.
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Paragraph 0046; 0070

(2018/04/02)

Production of monocyclic phenols by the liquid-phase hydrogenolysis of benzofuran and dibenzyl ether using in situ hydrogen production from methanol
We herein report our study into the hydrogenolysis of benzofuran, a model compound for the poorly decomposable compounds derived from lignin, over Pt supported catalysts in methanol in the absence of gaseous hydrogen. In this in situ hydrogenolysis reaction system, it was elucidated that both hydrogen production from methanol and selective hydrogenolysis of the furan moiety proceeded simultaneously to yield monophenolic compounds and gaseous hydrogen. This in situ hydrogenolysis reaction was investigated at temperatures between 180 and 220 °C and with reaction times ranging from 1 to 48 h. We found that the hydrogenolysis reaction was accelerated with increased hydrogen concentrations in the solvent. The molar ratio of consumed hydrogen to net hydrogen production increased gradually upon increasing the reaction temperature and time. In addition, the in situ hydrogenolysis of benzofuran under a hydrogen gas atmosphere revealed that the hydrogen produced in situ was more effective in the reaction than gaseous hydrogen, likely due to the dissolution and diffusion resistances of the solvent. Furthermore, dibenzyl ether was hydrogenolyzed to give monocyclic aromatic compounds under the same reaction conditions, suggesting that this in situ hydrogenolysis process could be effective in converting the by-products obtained during lignin depolymerization into valuable aromatic compounds.
Fujitsuka, Hiroyasu,Tamura, Masaki,Tago, Teruoki
p. 213 - 218
(2017/09/06)

Hydrogenolysis of lignin model compounds into aromatics with bimetallic Ru-Ni supported onto nitrogen-doped activated carbon catalyst
Lignin is the most abundant and renewable resources for production of natural aromatics. In this paper, new bimetallic catalytic system of Ru and Ni supported onto nitrogen-doped activated carbon (Ru-Ni-AC/N) was developed and its performances on hydrogenolysis of lignin model compounds under mild reaction conditions (1.0 MPa, 230 °C, in aqueous) were investigated. The results indicate that Ru-Ni-AC/N was a highly active, selective and stable catalyst for the conversion of lignin model compounds into aromatics, e.g. phenol, benzene and their derivatives. As verified by BET, XRD, HRTEM, XPS, H2-TPR and ICP-MS, the strong synergistic effects between i) Ru and Ni and ii) metals and N-groups were contributed to its excellent aromatics selectivity. What's more, the introduction of electron rich N atoms on AC was beneficial to the stabilization of metal particles, which greatly enhanced the durability of the catalyst.
Hu, Yinghui,Jiang, Guangce,Xu, Guoqiang,Mu, Xindong
p. 316 - 326
(2018/01/05)

A Practical and Chemoselective Ammonia-Free Birch Reduction
A novel protocol for a significantly improved, practical, and chemoselective ammonia-free Birch reduction mediated by bench-stable sodium dispersions and recoverable 15-crown-5 ether is reported. A broad range of aromatic and heteroaromatic compounds is reduced with excellent yields.
Lei, Peng,Ding, Yuxuan,Zhang, Xiaohe,Adijiang, Adila,Li, Hengzhao,Ling, Yun,An, Jie
supporting information
p. 3439 - 3442
(2018/06/26)

Novel electronic salt system and method for reducing unsaturated hydrocarbon compound
The invention discloses an electronic salt system and a method for reducing unsaturated hydrocarbon compounds by using the electronic salt system, belongs to the field of organic synthesis, and solvesthe problems such as complicated operation, harsh conditions, easy generation of complex over-reduction products of methods for reducing the unsaturated hydrocarbon compounds in the prior art. An electron salt may be synthesized by an alkali metal reagent, an ether and an alcohol, the ether can be a crown ether or a cryptand; and the method adopts the electronic salt system, the unsaturated hydrocarbon compounds is reduced by the electronic salt system in an organic solvent. The method for reducing the unsaturated hydrocarbon compounds is used for reducing the unsaturated hydrocarbon compounds.
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Paragraph 0159-0163

(2018/09/08)

Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
The OsVI nitrido complex, OsVI(N)(quin)2(OTs) (1, quin=2-quinaldinate, OTs=tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 at room temperature. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93 % to 98 %. Moreover, turnover numbers up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.
Kwong, Hoi-Ki,Lo, Po-Kam,Yiu, Shek-Man,Hirao, Hajime,Lau, Kai-Chung,Lau, Tai-Chu
supporting information
p. 12260 - 12263
(2017/09/06)

METHOD FOR PREPARING P-HYDROXYMANDELIC COMPOUNDS IN STIRRED REACTORS
The process allows the preparation of a p-hydroxymandelic compound, comprising at least one step of condensation of at least one aromatic compound bearing at least one hydroxyl group and whose para position is free, with glyoxylic acid, the condensation reaction being performed in at least one reactor equipped with at least one mixing means, the specific mixing power being between 0.1 kW/m3 and 15 kW/m3. In addition, the invention also relates to a process for preparing a 4-hydroxyaromatic aldehyde by oxidation of this p-hydroxymandelic compound.
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(2017/07/14)

Reductive Cleavage of C—O Bond in Model Compounds of Lignin
A simple protocol for reductive cleavage of C—O bond in diaryl and aryl methyl ethers was reported, in which NaH served as a reducing agent and KOtBu as a base and a radical initiator. The combination of NaH and KOtBu displayed high efficiency for reductive cleavage of C—O bond in diaryl and aryl ethers (e.g., dibenzofuran, diphenyl ether, anisole) without the hydrogenation of the aryl rings, in the absence of any other catalysts or ligands at 140 °C, producing corresponding arenes and phenols. It was indicated that the reaction was under a radical mechanism.
Xu, Huanjun,Liu, Xinwei,Zhao, Yanfei,Wu, Cailing,Chen, Yu,Gao, Xiang,Liu, Zhimin
p. 938 - 942
(2017/06/28)

Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
Novel Mg-bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid-phase selective methylation of phenol with methanol to produce o- and p-cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo- and regioselectivity (>95 % for p-product) was attained on the alkylation of phenol with bulky tert-butyl alcohol, rendering the first acid–base cooperative shape-selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape-selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.
Xie, Jingyan,Zhuang, Wenxia,Zhang, Wei,Yan, Ning,Zhou, Yu,Wang, Jun
p. 1076 - 1083
(2017/03/27)

Direct hydroxylation of benzene and aromatics with H2O2 catalyzed by a self-assembled iron complex: Evidence for a metal-based mechanism
An iminopyridine Fe(ii) complex, easily prepared in situ by self-assembly of cheap and commercially available starting materials (2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2 : 2 : 1 ratio), is shown to be an effective catalyst for the direct hydroxylation of aromatic rings with H2O2 under mild conditions. This catalyst shows a marked preference for aromatic ring hydroxylation over lateral chain oxidation, both in intramolecular and intermolecular competitions, as long as the arene is not too electron poor. The selectivity pattern of the reaction closely matches that of electrophilic aromatic substitutions, with phenol yields and positions dictated by the nature of the ring substituent (electron-donating or electron-withdrawing, ortho-para or meta-orienting). The oxidation mechanism has been investigated in detail, and the sum of the accumulated pieces of evidence, ranging from KIE to the use of radical scavengers, from substituent effects on intermolecular and intramolecular selectivity to rearrangement experiments, points to the predominance of a metal-based SEAr pathway, without a significant involvement of free diffusing radical pathways.
Capocasa, Giorgio,Olivo, Giorgio,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
p. 5677 - 5686
(2017/12/07)

Aromatic hydroxylation using an oxo-bridged diiron(III) complex: A bio-inspired functional model of toluene monooxygenases
In biology, aromatic hydroxylation is carried out using a family of heme and nonheme oxygenases, such as cytochrome P450, toluene monooxygenases (TMOs), and methane monooxygenase (MMO). In contrast, a vast majority of synthetic iron based catalysts employed so far in aromatic hydroxylation are monomeric in nature. Herein, we have employed a diferric complex of an aminopyridine ligand ([(bpmen)2Fe2O(μ-O)(μ-OH)](ClO4)3 (2), bpmen = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) towards aromatic hydroxylation with H2O2 and acetic acid. The diiron(iii) complex shows promising reactivity in the hydroxylation of benzene and alkylbenzenes with a higher selectivity towards aromatic ring hydroxylation over alkyl chain oxidation. The μ-oxo diiron(iii) core has been shown to be regenerated at the end of catalytic turnover. However, mechanistic studies indicate that the diiron(iii) complex undergoes dissociation into its monomeric congener and the resulting iron(iii) complex mitigates aromatic hydroxylation.
Kejriwal, Ambica,Bandyopadhyay, Pinaki,Biswas, Achintesh N.
p. 17261 - 17267
(2015/10/12)

Catalytic Oxidation of Alkanes and Alkenes by H2O2 with a μ-Oxido Diiron(III) Complex as Catalyst/Catalyst Precursor
A new μ-oxo diiron(III) complex of the lithium salt of the pyridine-based unsymmetrical ligand 3-[(3-{[bis(pyridin-2-ylmethyl)amino]methyl}-2-hydroxy-5-methylbenzyl)(pyridin-2-ylmethyl)amino]propanoate (LiDPCPMPP), [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, has been synthesized and characterized. The ability of the complex to catalyze oxidation of several alkanes and alkenes has been investigated by using CH3COOH/H2O2 (1:1) as an oxidative system. Moderate activity in cyclohexane oxidation (TOF = 33 h-1) and good activity in cyclohexene oxidation (TOF = 72 h-1) were detected. Partial retention of configuration (RC = 53%) in cis- and trans-1,2-dimethylcyclohexane oxidation, moderate 3/2 selectivity (4.1) in adamantane oxidation, and the observation of a relatively high kinetic isotope effect for cyclohexane oxidation (KIE = 3.27) suggest partial metal-based oxidation, probably in tandem with free-radical oxidation. Low-temperature UV/Vis spectroscopy and mass spectrometric studies in the rapid positive detection mode indicate the formation of a transient peroxido species, [Fe2(O)(O2)(LiDPCPMPP)2]2+, which might be an intermediate in the metal-based component of the oxidation process. A μ-oxido diiron(III) complex, [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, was synthesized and characterized. This complex was used as catalyst in C-H bond oxidation with CH3COOH-H2O2 as chemical oxidant. Reactivity studies indicate that the oxidation process goes through a metal-based mechanism concomitant with a radical process.
Das, Biswanath,Al-Hunaiti, Afnan,Haukka, Matti,Demeshko, Serhiy,Meyer, Steffen,Shteinman, Albert A.,Meyer, Franc,Repo, Timo,Nordlander, Ebbe
p. 3590 - 3601
(2015/08/06)

Selective catalytic conversion of guaiacol to phenols over a molybdenum carbide catalyst
An activated carbon supported α-molybdenum carbide catalyst (α-MoC1-x/AC) showed remarkable activity in the selective deoxygenation of guaiacol to substituted mono-phenols in low carbon number alcohol solvents. Combined selectivities of up to 85% for phenol and alkylphenols were obtained at 340°C for α-MoC1-x/AC at 87% conversion in supercritical ethanol. The reaction occurs via consecutive demethylation followed by a dehydroxylation route instead of a direct demethoxygenation pathway.
Ma, Rui,Cui, Kai,Yang, Le,Ma, Xiaolei,Li, Yongdan
supporting information
p. 10299 - 10301
(2015/06/25)

Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by Pyridylalkylamine Ligands
Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence of a catalytic amount of the nickel complex [NiII(tepa)]2+ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60°C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H218O2 was utilized as the oxidant, 18O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.
Morimoto, Yuma,Bunno, Shuji,Fujieda, Nobutaka,Sugimoto, Hideki,Itoh, Shinobu
supporting information
p. 5867 - 5870
(2015/05/27)

Activity investigation of imidazolium-based ionic liquid as catalyst for friedel-crafts alkylation of aromatic compounds
N-Methylimidazolium ionic liquids were synthesised from N-methylimidazole and 1-bromobutane by two-step method. The alkylation of benzene and other aromatic compounds through improved Friedel-Crafts reaction was investigated in these ionic liquids. The imidazolium-based ionic liquids showed both high activity and high selectivity for this reaction. In particular, remarkable enhancement of the catalytic effect of the imidazolium-based ionic liquids was observed for the ionic liquids containing the PF6- anion. The effects of various types of anions, ionic liquid dosage, reaction temperature and molar ratio of aromatic compound to 1-bromobutane/tertbutyl alcohol were explored using [Bmim]PF6 or its mixture with AlCl3 as catalyst. The synthesis yielded improved results over those obtained using either neat AlCl3 or other imidazolium-based ionic liquids as catalyst. The ionic liquids can also be recycled and reused in contrast to traditional solvent-catalyst systems.
Cai, Mingjian,Wang, Xiuge
p. 649 - 653
(2015/01/30)

Catalytic decomposition of 2,3-dihydrobenzofuran to monocyclic compounds over palladium catalysts supported on sulfonated ordered mesoporous carbon
Ordered mesoporous carbon (OMC) was sulfonated at different temperature (OMC-SO3H-X, X =125, 150, 175, 200, and 225 °C) in order to provide acid sites to OMC. Palladium catalysts were then supported on OMC-SO3H-X by an incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monocyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. In the catalytic decomposition of 2,3-dihydrobenzofuran over Pd/OMC-SO3H-X, ethylcyclohexane and 2-ethlyphenol were mainly produced. Conversion of 2,3-dihydrobenzofuran and total yield for main products (ethylcyclohexane and 2-ethylphenol) were closely related to the acidity of the catalysts. Conversion of 2,3-dihydrobenzofuran and total yield for main products increased with increasing acidity of Pd/OMC-SO3H-X catalysts. Among the catalysts tested, Pd/OMC-SO3H-150 with the largest acidity showed the highest conversion of 2,3-dihydrobenzofuran and the highest total yield for main products.
Kim, Jeong Kwon,Park, Hai Woong,Hong, Ung Gi,Lee, Yoon Jae,Song, In Kyu
p. 9139 - 9144
(2015/11/03)

Scope and Mechanistic Analysis for Chemoselective Hydrogenolysis of Carbonyl Compounds Catalyzed by a Cationic Ruthenium Hydride Complex with a Tunable Phenol Ligand
A cationic ruthenium hydride complex, [(C6H6)(PCy3)(CO)RuH]+BF4- (1), with a phenol ligand was found to exhibit high catalytic activity for the hydrogenolysis of carbonyl compounds to yield the corresponding aliphatic products. The catalytic method showed exceptionally high chemoselectivity toward the carbonyl reduction over alkene hydrogenation. Kinetic and spectroscopic studies revealed a strong electronic influence of the phenol ligand on the catalyst activity. The Hammett plot of the hydrogenolysis of 4-methoxyacetophenone displayed two opposite linear slopes for the catalytic system 1/p-X-C6H4OH (ρ = -3.3 for X = OMe, t-Bu, Et, and Me; ρ = +1.5 for X = F, Cl, and CF3). A normal deuterium isotope effect was observed for the hydrogenolysis reaction catalyzed by 1/p-X-C6H4OH with an electron-releasing group (kH/kD = 1.7-2.5; X = OMe, Et), whereas an inverse isotope effect was measured for 1/p-X-C6H4OH with an electron-withdrawing group (kH/kD = 0.6-0.7; X = Cl, CF3). The empirical rate law was determined from the hydrogenolysis of 4-methoxyacetophenone: rate = kobsd[Ru][ketone][H2]-1 for the reaction catalyzed by 1/p-OMe-C6H4OH, and rate = kobsd[Ru][ketone][H2]0 for the reaction catalyzed by 1/p-CF3-C6H4OH. Catalytically relevant dinuclear ruthenium hydride and hydroxo complexes were synthesized, and their structures were established by X-ray crystallography. Two distinct mechanistic pathways are presented for the hydrogenolysis reaction on the basis of these kinetic and spectroscopic data. (Chemical Equation Presented).
Kalutharage, Nishantha,Yi, Chae S.
supporting information
p. 11105 - 11114
(2015/09/15)

One step C-N bond formation from alkylbenzene and ammonia over Cu-modified TS-1 zeolite catalyst
A Cu doped TS-1 zeolite sample was applied to catalyze the formation of C-N bonds on both the ring and the side chain of toluene, as well as other alkylbenzenes. A yield of 3.4% of toluidine was obtained for the amination of toluene, with a 1.0% yield of nitrobenzene. Cyanobenzene was also obtained as the C-N bond product on the side chain with a yield of 1.0%. The selectivity for C-N bond formation was 52.4%. The catalyst promoted the formation of a hydroxylamine intermediate from ammonia and hydrogen peroxide, and then the instantaneously generated amino cation reacted with the substrate to form C-N bonds on both the ring and side chain. Cyanobenzene was produced from the dehydration of benzylamine, formed via the reaction of ammonia and toluene. The formation of C-N bonds on the ring had an ortho-orientation advantage for mono-substituted-benzenes. With the increase in the number of methyl substituents, the yield of the ring products decreased, which might be caused by steric hindrance. the Partner Organisations 2014.
Xia, Sheng,Yu, Tianhua,Liu, Huihui,Li, Guiying,Hu, Changwei
p. 3108 - 3119
(2014/08/18)

Catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds over Pd/XCs2.5H0.5PW12O 40/OMC (ordered mesoporous carbon) (X = 10-30 wt.%) catalysts
A series of Pd/XCs2.5H0.5PW12O 40/OMC (ordered mesoporous carbon) (X = 10, 15, 20, 25, and 30 wt.%) catalysts with different Cs2.5H0.5PW12O 40 contents (X, wt%) were prepared by a sequential incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. Acidity of Pd/XCs2.5H0.5PW12O40/OMC catalysts served as an important factor determining the catalytic performance in the reaction. Conversion of 2,3-dihydrobenzofuran and total yield for main products (2-ethylphenol and ethylcyclohexane) increased with increasing acidity of Pd/XCs2.5H0.5PW12O40/OMC catalysts.
Kim, Jeong Kwon,Park, Hai Woong,Hong, Ung Gi,Lee, Yoon Jae,Song, Ji Hwan,Song, In Kyu
p. 68 - 72
(2014/03/21)

CsxH3-0-xPW12O40 (X = 2.0-3.0) heteropolyacid nano-catalysts for catalytic decomposition of 2,3-dihydrobenzofuran to aromatics
Cesium-exchanged CsxH3-0-xPW12O40 (X = 2.0, 2.3, 2.5, 2.8, and 3.0) heteropolyacid nanocatalysts were prepared, and they were applied to the catalytic decomposition of lignin model compound to aromatics. Success
Kim, Jeong Kwon,Park, Hai Woong,Hong, Ung Gi,Choi, Jung Ho,Song, In Kyu
p. 8884 - 8890
(2015/02/19)

Selective synthesis of p-ethylphenol by gas-phase alkylation of phenol with ethanol
The selective synthesis of p-ethylphenol from gas-phase alkylation of phenol with ethanol was studied on zeolites HZSM5 and HMCM22 at 523 K. Phenol reacted directly with ethanol to form ethylphenylether by O-alkylation, and p- and o-ethylphenol isomers by C-alkylation; secondary products were m-ethylphenol and dialkylated compounds. Both zeolites presented similar activity and formed low amounts of ethylphenylether and dialkylated products, but exhibited different ethylphenol isomers distribution. In fact, for a contact time of 99.3gh/mol the selectivity to p-ethylphenol was 51.4% on HMCM22 and only 14.2% on HZSM5. The superior performance of zeolite HMCM22 for selectively producing p-ethylphenol was due to its narrower pore channels that suppressed the formation of dialkylated products and hampered by diffusional constraints the formation of o-ethylphenol. The maximum p-ethylphenol yield obtained on HMCM22 was 41% at a contact time of 250gh/mol; for higher contact times, p-ethylphenol was increasingly converted to m-ethylphenol. All the samples deactivated on stream because of coke formation. The carbon amount built on HMCM22 diminished when contact time was increased thereby indicating that coke was mainly formed from the reactants. Additional catalytic runs showed that phenol was the main responsible of catalyst deactivation, probably because of its strong adsorption on surface active sites.
Sad,Duarte,Padró,Apesteguía
p. 77 - 84
(2015/09/28)

Highly selective reductive cleavage of aromatic carbon-oxygen bonds catalyzed by a cobalt compound
A cobalt catalyst has been demonstrated, for the first time, to be effective for the reductive cleavage of inert aromatic CO bonds with high selectivity. Compared with previous Ni catalysts, the cobalt catalyst reported here is more commercially available and air-stable.
Ren, Yun-Lai,Tian, Ming,Tian, Xin-Zhe,Wang, Qian,Shang, Huantao,Wang, Jianji,Zhang, Z. Conrad
p. 36 - 39
(2014/05/20)

Deoxygenation of α,β-unsaturated acylphenols through ethyl o-acylphenylcarbonates with Luche reduction
An efficient protocol for deoxygenation of α,β-unsaturated acylphenols through ethyl o-acylphenylcarbonates with Luche reduction is described. The reaction shows very good selectivity and tolerates a wide range of functionalities on α,β-unsaturated acylphenols, giving corresponding 2-allylphenols in good to excellent yields.
Yuan, Hu,Chen, Hao,Jin, Huizi,Li, Bo,Yue, Rongcai,Ye, Ji,Shen, Yunheng,Shan, Lei,Sun, Qingyan,Zhang, Weidong
supporting information
p. 2776 - 2780
(2013/06/05)

Selective reductive cleavage of inert aryl C-O bonds by an iron catalyst
Breaking point: An effective reductive cleavage of inert aryl C-O bonds with an inexpensive iron catalyst has been developed. During this process, the reduction of the arene rings was not observed. This catalytic system also enabled the selective cleavage of the β-O-4 linkage of lignin model compounds under an atmosphere of hydrogen, thus offering an opportunity for the depolymerization of lignin. Copyright
Ren, Yunlai,Yan, Mengjie,Wang, Jianji,Zhang, Z. Conrad,Yao, Kaisheng
supporting information
p. 12674 - 12678
(2013/12/04)

Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
Peroxide in, phenol out: The catalyst [-PW10O38V 2(μ-OH)2]3- showed high activity in the hydroxylation of various aromatic compounds with aqueous H2O 2. The system was regioselective, producing para-phenols from monosubstituted benzene derivatives. Furthermore, alkylarenes with reactive side-chain Ca spa 3-H bonds could be chemoselectively hydroxylated without significant formation of side-chain oxygenated products. Copyright
Kamata, Keigo,Yamaura, Taiyo,Mizuno, Noritaka
supporting information; scheme or table
p. 7275 - 7278
(2012/08/28)

CoMo sulfide-catalyzed hydrodeoxygenation of lignin model compounds: An extended reaction network for the conversion of monomeric and dimeric substrates
In the present work, extensive hydrodeoxygenation (HDO) studies with a commercial sulfided CoMo/Al2O3 catalyst were performed on a library of lignin model compounds at 50 bar hydrogen pressure and 300 °C in dodecane, using a batch autoclave system. The catalyst was activated under hydrogen atmosphere prior to the reaction, and the spent catalyst was analyzed using thermogravimetric analysis. An extended reaction network is proposed, showing that HDO, demethylation, and hydrogenation reactions take place simultaneously. HDO of mono-oxygenated substrates proved to be difficult at the applied conditions. Starting from most positions in the network, phenol, and cresols are therefore the main final products, suggesting the possibility of convergence on a limited number of products from a mixture of substrates. HDO of dimeric model compounds mimicking typical lignin linkages revealed that coumaran alkyl ethers and β-O-4 bonds can be broken, but 5-5′ linkages not.
Jongerius, Anna L.,Jastrzebski, Robin,Bruijnincx, Pieter C.A.,Weckhuysen, Bert M.
scheme or table
p. 315 - 323
(2012/03/10)

PROCESS FOR PREPARING ALKYLATED HYDROXYAROMATICS IN MICROREACTORS
A process is proposed for preparing hydroxyaromatics by heterogeneous catalytic reaction of hydroxyaromatics with C1-C4-alkanols in a microreactor (10), comprising the steps of: a) introducing the hydroxyaromatic and at least one compound selected from the group consisting of C1-C4-alkanols as reactants into at least one inlet orifice (22) of the microreactor (10) comprising at least one microreactor unit (18),b) passing the reactants through at least one microreactor unit (18) of the microreactor (10), said unit comprising a multitude of microchannels (28), said microchannels (28) having a lateral extent of less than 1 mm, and a heterogeneous catalyst being incorporated in the microchannels (28) for conversion of the reactants,c) passing the hydroxyaromatics prepared out through at least one outlet orifice (24) of the microreactor (10).
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(2012/09/25)

Reductive dealkylation of anisole and phenetole: Towards practical lignin conversion
We present and develop alternative catalysts for biomass conversion and specifically lignin conversion into aromatics. Unlike the conventional CoMo and NiMo formulations, our catalysts can convert low-sulfur feedstocks. A set of five magnesia-alumina mixed oxides were screened in the hydrodealkylation of alkyl phenyl ethers as lignin model compounds. The typical selectivity to phenol is 30-75 %. Interestingly, we saw that the more basic the catalyst, the higher the selectivity for phenol. The results concur with the formation of phenoxide (PhO-) and RH3+ fragments on the catalyst surface. These can then react with H+ and H- species formed by the hydrogen dissociation on the MgO surface, giving phenol and hydrocarbons. We conclude that magnesia-alumina mixed oxides are attractive candidates for catalyzing lignin breakdown. These catalysts are highly stable, inexpensive, and readily available .
Strassberger, Zea,Tanase, Stefania,Rothenberg, Gadi
experimental part
p. 5246 - 5249
(2011/11/12)

Iron-catalyzed reductive dehydroxylation of benzylic alcohols using polymethylhydrosiloxane (PMHS)
The combination of FeCl3 and PMHS is an efficient reducing system for the selective dehydroxylation of secondary benzylic alcohols, even in the presence of carbonyls, under very mild conditions. Georg Thieme Verlag Stuttgart · New York.
Chan, Li Yan,Lim, Jazreel Seh Kai,Kim, Sunggak
experimental part
p. 2862 - 2866
(2012/01/11)

Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
Makhlynets, Olga V.,Rybak-Akimova, Elena V.
supporting information; experimental part
p. 13995 - 14006
(2011/04/12)