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Molybdenum-Catalyzed Deoxygenation Coupling of Lignin-Derived Alcohols for Functionalized Bibenzyl Chemicals
With the growing demand for sustainability and reducing CO2 footprint, lignocellulosic biomass has attracted much attention as a renewable, carbon-neutral and low-cost feedstock for the production of chemicals and fuels. To realize efficient utilization of biomass resource, it is essential to selectively alter the high degree of oxygen functionality of biomass-derivates. Herein, we introduced a novel procedure to transform renewable lignin-derived alcohols to various functionalized bibenzyl chemicals. This strategy relied on a short deoxygenation coupling pathway with economical molybdenum catalyst. A well-designed H-donor experiment was performed to investigate the mechanism of this Mo-catalyzed process. It was proven that benzyl carbon-radical was the most possible intermediate to form the bibenzyl products. It was also discovered that the para methoxy and phenolic hydroxyl groups could stabilize the corresponding radical intermediates and then facilitate to selectively obtain bibenzyl products. Our research provides a promising application to produce functionalized aromatics from biomass-derived materials.
Jiang, Huifang,Lu, Rui,Luo, Xiaolin,Si, Xiaoqin,Xu, Jie,Lu, Fang
supporting information
p. 1292 - 1296
(2020/12/09)

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
(2022/01/08)

Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
p. 13337 - 13347
(2021/11/20)

Can Heteroarenes/Arenes Be Hydrogenated Over Catalytic Pd/C Under Ambient Conditions?
Hydrogenation of over a dozen aromatic compounds, including both heteroarenes and arenes, over palladium on carbon (Pd/C, 1–100 molpercent) with H2-balloon pressure at room temperature is reported. Analyses using pyridine as a model substrate revealed that acetic acid was the best solvent, as using only 1 molpercent Pd/C provided piperidine quantitatively. Substrate scope analysis and density functional theory calculations indicated that reaction rates are highly dependent on frontier molecular orbital characteristics and the steric bulkiness of substituents. Moreover, the established method was used for the concise synthesis of the anti-Alzheimer drug donepezil (Aricept?).
Tanaka, Nao,Usuki, Toyonobu
p. 5514 - 5522
(2020/07/24)

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)

Decyanation method of nitrile organic compound
The invention provides a decyanation method of a nitrile organic compound. The nitrile organic compound shown in a general formula (1), a sodium reagent, crown ether and a proton donor are subjected to decyanation reaction in an organic solvent I to generate an organic compound shown in a general formula (2). According to the method, a Na/15-crown-5/H2O system is adopted, so that nitrile organic matters can be converted into a decyanation product, and the generation of amine byproducts is inhibited. The new method does not need to use liquid ammonia as a solvent, and is safer and more convenient to operate. The required sodium dispersoid is low in price; and the 15-crown-5 can be recycled and repeatedly used. The method has the advantages of good chemical selectivity, wide substrate application range, good functional group compatibility and the like.
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Paragraph 0067-0074

(2020/02/10)

Reductive Cleavage of Unactivated Carbon-Cyano Bonds under Ammonia-Free Birch Conditions
A general protocol for the reductive cleavage of unactivated carbon-cyano bonds in aliphatic nitriles has been achieved under single-electron-transfer conditions using Na/15-crown-5/H2O. Electron is supplied by the electride derived from bench-stable sodium dispersions and recoverable 15-crown-5. H2O provides the proton source and suppresses the reduction of aromatic moieties. Compared with the Na/NH3 electride system generated under traditional Birch conditions, this ammonia-free electride system is more practical and features better reactivity and chemoselectivity for the decyanations of a broad range of aliphatic nitriles.
An, Jie,Ding, Yuxuan,Luo, Shihui,Ma, Lifu
(2019/11/29)

Selective, Catalytic, and Metal-Free Coupling of Electron-Rich Phenols and Anilides Using Molecular Oxygen as Terminal Oxidant
Selective oxidative homo- and cross-coupling of electron-rich phenols and anilides was developed using nitrosonium tetrafluoroborate as a catalyst. Oxidative coupling of phenols revealed unusual selectivities, which translated into the unprecedented synthesis of inverse Pummerer-type ketones. Mechanistic studies suggest that oxidative coupling of phenols and anilides shares a common pathway via homolytical heteroatom-hydrogen bond cleavage. Nitrosonium salt catalysis was applied for cross-dehydrogenative coupling initiated by generation of heteroatom-centered radicals.
Bering, Luis,Vogt, Melina,Paulussen, Felix M.,Antonchick, Andrey P.
supporting information
p. 4077 - 4080
(2018/07/15)

Two Stereoinduction Events in One C?H Activation Step: A Route towards Terphenyl Ligands with Two Atropisomeric Axes
Herein we disclose the synthesis of original chiral scaffolds—ortho-orientated terphenyls presenting two atropisomeric Ar–Ar axes. These unusual structures were built up by using the C?H activation approach, and remarkably, both chiral axes were controlled with excellent stereoselectivity in a single transformation. During the reaction, not only does atroposelective functionalization of a biaryl precursor occur to establish one stereogenic axis, but an unprecedented atropo-stereoselective C?H arylation also takes place to generate the second stereogenic element. These enantiomerically pure ortho-terphenyls show an original tridimensional structure and thus constitute a unique foundation for building up a library of enantiomerically pure bidentate ligands, such as the new ligands S/N-Biax and diphosphine BiaxPhos.
Dherbassy, Quentin,Djukic, Jean-Pierre,Wencel-Delord, Joanna,Colobert, Fran?oise
supporting information
p. 4668 - 4672
(2018/03/21)

Ormetoprim synthesis method
The invention provides an ormetoprim synthesis method. The method includes steps: subjecting p-cresol and dimethyl carbonate to phenolic hydroxymethylation to obtain a compound I; subjecting the compound I and potassium bromide to bromination reaction under an acetic anhydride-nitric acid system to obtain a compound II; taking cuprous chloride as a catalyst, and subjecting the compound II and sodium methylate methanol solution to methoxylation reaction to obtain a compound III; subjecting the compound III and a VHA reagent to formylation reaction to obtain a compound IV; subjecting the compound IV to reaction with sodium methylate and acrylonitrile methanol solution to obtain a compound V; after the compound V is subjected to alkali isomerization to obtain a vinyl ether structure, subjecting to addition reaction with methyl alcohol and direct condensation and cyclization with guanidine to finally obtain a compound VI which is a final product namely ormetoprim. Defects in the prior art are overcome, and the provided ormetoprim synthesis method has advantages of technical simplicity, easiness in acquisition of starting materials, high yield and low production cost.
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Paragraph 0048; 0049

(2017/11/16)

Manganese-Catalyzed Direct Deoxygenation of Primary Alcohols
Deoxygenation of alcohols is an important tool in the repertoire of defunctionalization methods in modern synthetic chemistry. We report the base-metal-catalyzed direct deoxygenation of benzylic and aliphatic primary alcohols via oxidative dehydrogenation/Wolff-Kishner reduction. The reaction is catalyzed by a well-defined PNP pincer complex of Earth-abundant manganese, evolving H2, N2, and water as the only byproducts.
Bauer, Jonathan O.,Chakraborty, Subrata,Milstein, David
p. 4462 - 4466
(2017/07/24)

A process for preparing 5 - substituted benzyl - 2, 4 - diamino pyrimidine and its derivatives (by machine translation)
The invention discloses a process for preparing 5 - substituted benzyl - 2, 4 - diamino pyrimidine and derivatives thereof, in particular can be used for preparing omay pullin, b a oxygen animal pen amine pyrimidine, such as palestinian kuikui purin. The invention relates to 5 - hydroxymethyl uracil as raw materials, through the electrophilic substitution reaction, chlorinated, amino and hydrolysis step preparation 5 - substituted benzyl - 2, 4 - diamino pyrimidine and its derivatives. The method can be used for preparing various 5 - substituted benzyl - 2, 4 - diaminopyrimidines of the molecule, thereby avoiding the high-pressure reaction step, the safety is high, and is suitable for industrial production. (by machine translation)
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Paragraph 0049; 0052; 0056; 0060

(2018/01/11)

En Route to a Practical Primary Alcohol Deoxygenation
A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols.
Dai, Xi-Jie,Li, Chao-Jun
supporting information
p. 5433 - 5440
(2016/05/19)

Tandem catalytic depolymerization of lignin by water-tolerant Lewis acids and rhodium complexes
Lignin is an attractive renewable feedstock for aromatic bulk and fine chemicals production, provided that suitable depolymerization procedures are developed. Here, we describe a tandem catalysis strategy for ether linkage cleavage within lignin, involving ether hydrolysis by water-tolerant Lewis acids followed by aldehyde decarbonylation by a Rh complex. In situ decarbonylation of the reactive aldehydes limits loss of monomers by recondensation, a major issue in acid-catalyzed lignin depolymerization. Rate of hydrolysis and decarbonylation were matched using lignin model compounds, allowing the method to be successfully applied to softwood, hardwood, and herbaceous dioxasolv lignins, as well as poplar sawdust, to give the anticipated decarbonylation products and, rather surprisingly, 4-(1-propenyl)phenols. Promisingly, product selectivity can be tuned by variation of the Lewis-acid strength and lignin source.
Jastrzebski, Robin,Constant, Sandra,Lancefield, Christopher S.,Westwood, Nicholas J.,Weckhuysen, Bert M.,Bruijnincx, Pieter C.A.
p. 2074 - 2079
(2017/07/25)

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)

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)

A ligand-free, powerful, and practical method for methoxylation of unactivated aryl bromides by use of the CuCl/HCOOMe/MeONa/MeOH system
A ligand-free, powerful, and practical method for mono and polymethoxylation of unactivated aryl bromides has been developed; CuCl was used as catalyst, HCOOMe as cocatalyst, and methanolic MeONa as both nucleophile and solvent. This eco-friendly procedure is characterized by operational simplicity, inexpensive substrates (unactivated mono to polybromoarenes), full conversion, and direct recovery of pure MeOH.
Guo, Ying,Ji, Si-Zhe,Chen, Cheng,Liu, Hong-Wei,Zhao, Jian-Hong,Zheng, Yu-Lin,Ji, Ya-Fei
p. 8651 - 8664
(2015/03/05)

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.
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Page/Page column 36

(2015/04/28)

Erbium trifluoromethanesulfonate catalyzed Friedel-Crafts acylation using aromatic carboxylic acids as acylating agents under monomode-microwave irradiation
Erbium trifluoromethanesulfonate is found to be a good catalyst for the Friedel-Crafts acylation of arenes containing electron-donating substituents using aromatic carboxylic acids as the acylating agents under microwave irradiation. An effective, rapid and waste-free method allows the preparation of a wide range of aryl ketones in good yields and in short reaction times with minimum amounts of waste.
Tran, Phuong Hoang,Hansen, Poul Erik,Nguyen, Hai Truong,Le, Thach Ngoc
p. 612 - 618
(2015/02/19)

Rapid Wolff-Kishner reductions in a silicon carbide microreactor
Wolff-Kishner reductions are performed in a novel silicon carbide microreactor. Greatly reduced reaction times and safer operation are achieved, giving high yields without requiring a large excess of hydrazine. The corrosion resistance of silicon carbide avoids the problematic reactor compatibility issues that arise when Wolff-Kishner reductions are done in glass or stainless steel reactors. With only nitrogen gas and water as by-products, this opens the possibility of performing selective, large scale ketone reductions without the generation of hazardous waste streams.
Newman, Stephen G.,Gu, Lei,Lesniak, Christoph,Victor, Georg,Meschke, Frank,Abahmane, Lahbib,Jensen, Klavs F.
supporting information
p. 176 - 180
(2014/01/06)

On-line reaction monitoring and mechanistic studies by mass spectrometry: Negishi cross-coupling, hydrogenolysis, and reductive amination
Reaction monitoring using inductive ESI mass spectrometry allows chemical reactions to be tracked in real time, including air- and moisture-sensitive as well as heterogeneous reactions. Highly concentrated solutions can also be monitored for long periods without emitter clogging. Sheath gas assists in nebulization and a sample splitter reduces the delay time and minimizes contamination of the instrument. Short-lived intermediates (ca. 5 s) were observed in Pd/C-catalyzed hydrogenolysis, and several intermediates were seen in Negishi cross-coupling reactions. Fast and simple: A reaction monitoring system based on inductive ESI mass spectrometry provides a fast and simple way to monitor chemical reactions, including air-/moisture-sensitive reactions, continuously. It also provides information on solution-phase organic reaction mechanisms as shown by the observation of short-lived intermediates in Pd/C-catalyzed hydrogenolysis and several intermediates in Negishi cross-coupling reactions.
Yan, Xin,Sokol, Ewa,Li, Xin,Li, Guangtao,Xu, Shiqing,Cooks, R. Graham
supporting information
p. 5931 - 5935
(2014/06/10)

Catalytic depolymerization of alkali lignin in subcritical water: Influence of formic acid and Pd/C catalyst on the yields of liquid monomeric aromatic products
Alkali lignin was subjected to depolymerization in subcritical water at 265 °C, 6.5 MPa for reaction times between 1-6 h in a batch reactor and in the presence of formic acid (FA) and Pd/C catalyst. The oil products were extracted into diethyl ether and contained >90% of single-ring phenolic compounds. The reaction of lignin in subcritical water alone yielded 22.3 wt% oil containing 56% guaiacol as the main product. A maximum oil yield of 33.1 wt% was obtained when the lignin was reacted in the presence of formic acid alone. In the presence of FA, catechol became the predominant compound, with more than 80% of the ether extract after 6 h. The conversion of guaiacol to catechol in the presence of formic acid suggested the hydrolysis of O-CH3 ether bonds. In addition, the yields of alkyl guaiacols increased in the presence of FA. The use of 5 wt% Pd/C catalyst with FA slightly decreased the yields of oil products but led to compounds indicative of hydrogenolysis of aryl-O ether bonds as well as hydrogenation of CC bonds.
Onwudili, Jude A.,Williams, Paul T.
p. 4740 - 4748
(2014/12/11)

Iridium-catalyzed direct dehydroxylation of alcohols
Iridium-catalyzed direct dehydroxylation of alcohols with hydrazine was developed through a combination of the oxidation of alcohols and the Wolff-Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary, benzylic and allylic alcohols. Iridium-catalyzed direct dehydroxylation of alcohols with hydrazine is developed through a combination of the oxidation of alcohols and Wolff-Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary alcohols, especially benzylic and allylic ones. Copyright
Huang, Jian-Lin,Dai, Xi-Jie,Li, Chao-Jun
supporting information
p. 6496 - 6500
(2013/11/06)

N-Tosylhydrazine-mediated deoxygenative hydrogenation of aldehydes and ketones catalyzed by Pd/C
A mild and efficient method for the deoxygenative hydrogenation of aldehydes and ketones has been developed. The reaction is mediated by N-tosylhydrazine with H2 (1 atm) as the reductant and 10% Pd/C as the catalyst.
Zhou, Lei,Liu, Zhenxing,Liu, Yizhou,Zhang, Yan,Wang, Jianbo
p. 6083 - 6087
(2013/07/25)

Efficient anodic and direct phenol-arene C,C cross-coupling: The benign role of water or methanol
C,C cross-coupling reactions for the synthesis of nonsymmetrical biaryls represent one of the most significant transformations in contemporary organic chemistry. A variety of useful synthetic methods have been developed in recent decades, since nonsymmetrical biaryls play an evident role in natural product synthesis, as ligand systems in homogeneous catalysis and materials science. Transformation of simple arenes by direct C,H activation belongs to the cutting-edge strategies for creating biaryls; in particular the 2-fold C,H activation is of significant interest. However, in most examples very costly noble metal catalysts, ligand systems, and significant amount of waste-producing oxidants are required. Electrochemical procedures are considered as inherently "green" methods, because only electrons are required and therefore, no reagent waste is produced. Here, we report a metal-free electrochemical method for cross-coupling between phenols and arenes using boron-doped diamond (BDD) anodes in fluorinated media. Our sustainable approach requires no leaving functionalities. Employing water or methanol as mediator represents the key improvement for achieving nonsymmetrical biaryls with superb selectivity and synthetic attractive yields.
Kirste, Axel,Elsler, Bernd,Schnakenburg, Gregor,Waldvogel, Siegfried R.
supporting information; experimental part
p. 3571 - 3576
(2012/04/10)

A heterogeneous nickel catalyst for the hydrogenolysis of aryl ethers without arene hydrogenation
A heterogeneous nickel catalyst for the selective hydrogenolysis of aryl ethers to arenes and alcohols generated without an added dative ligand is described. The catalyst is formed in situ from the well-defined soluble nickel precursor Ni(COD)2 or Ni(CH2TMS)2(TMEDA) in the presence of a base additive, such as tBuONa. The catalyst selectively cleaves CAr-O bonds in aryl ether models of lignin without hydrogenation of aromatic rings, and it operates at loadings down to 0.25 mol % at 1 bar of H2 pressure. The selectivity of this catalyst for electronically varied aryl ethers differs from that of the homogeneous catalyst reported previously, implying that the two catalysts are distinct from each other.
Sergeev, Alexey G.,Webb, Jonathan D.,Hartwig, John F.
supporting information
p. 20226 - 20229
(2013/02/25)

CATALYTIC DISPROPORTIONATION AND CATALYTIC REDUCTION OF CARBON-CARBON AND CARBON-OXYGEN BONDS OF LIGNIN AND OTHER ORGANIC SUBSTRATES
The present invention provides methods and catalyst compositions for the catalytic reduction of carbon-oxygen bonds of organic substrates and the catalytic disproportionation of carbon-oxygen or carbon-carbon bonds of organic substrates. These methods and catalyst compositions may be used to depolymerize lignin. The disproportionation of carbon-oxygen or carbon-carbon bonds of organic substrates or lignin is carried out by cleaving a carbon-oxygen bond or a carbon-carbon bond in a catalytic disproportionation reaction. The catalysts may be formed from a metal precursor such as ruthenium or vanadium and a bidentate ligand The catalytic reduction of carbon-oxygen bonds of organic substrates such as lignin is carried out by cleaving a carbon-oxygen bond in the presence of a hydrogen atom source. Lignin fragments produced following depolymerization by such methods may be further processed into fuels.
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Page/Page column 124-126

(2011/02/24)

Selective, nickel-catalyzed hydrogenolysis of aryl ethers
Selective hydrogenolysis of the aromatic carbon-oxygen (C-O) bonds in aryl ethers is an unsolved synthetic problem important for the generation of fuels and chemical feedstocks from biomass and for the liquefaction of coal. Currently, the hydrogenolysis of aromatic C-O bonds requires heterogeneous catalysts that operate at high temperature and pressure and lead to a mixture of products from competing hydrogenolysis of aliphatic C-O bonds and hydrogenation of the arene. Here, we report hydrogenolyses of aromatic C-O bonds in alkyl aryl and diaryl ethers that form exclusively arenes and alcohols. This process is catalyzed by a soluble nickel carbene complex under just 1 bar of hydrogen at temperatures of 80 to 120°C; the relative reactivity of ether substrates scale as Ar-OAr?Ar-OMe>ArCH2-OMe (Ar, Aryl; Me, Methyl). Hydrogenolysis of lignin model compounds highlights the potential of this approach for the conversion of refractory aryl ether biopolymers to hydrocarbons.
Sergeev, Alexey G.,Hartwig, John F.
scheme or table
p. 439 - 443
(2011/10/31)

Couplings of benzylic halides mediated by titanocene chloride: Synthesis of bibenzyl derivatives
Titanocene monochloride catalyzes the homocoupling of benzylic halides and benzylic gem-dibromides to give the corresponding bibenzyl and stilbenyl systems. Exposure of benzylic bromides to Ti(III) in the presence of aldehydes gave rise to the Barbier-type products. Examples of the utility of the herein described processes are included.
Barrero, Alejandro F.,Herrador, M. Mar,Del Moral, Jose F. Quilez,Arteaga, Pilar,Akssira, Mohammed,El Hanbali, Fadwa,Arteaga, Jesus F.,Dieguez, Horacio R.,Sanchez, Elena M.
p. 2251 - 2254
(2007/10/03)

A solvent-controlled highly efficient Pd-C catalyzed hydrogenolysis of benzaldehydes to methylbenzenes via a novel 'acetal pathway'
Pd-C catalyzed hydrogenolysis of benzaldehydes to methylbenzenes has been described to proceed via a 'benzenemethanol pathway'. In this article, a novel 'acetal pathway' was first revealed by a systematic study when lower alcohols were used as solvents and a solvent-controlled highly efficient procedure was established.
Xing, Lixin,Wang, Xinyan,Cheng, Chuanjie,Zhu, Rui,Liu, Bo,Hu, Yuefei
p. 9382 - 9386
(2008/02/10)

Process development of the synthesis of 3,4,5-trimethoxytoluene
3,4,5-Trimethoxytoluene (TMT) was synthesized, starting from p-cresol, through bromination followed by methylation to give 3,5-dibromo-4-methoxytoluene (DBMT). The methoxylation of the latter with sodium methoxide in methanol was studied under pressure and by continuous distillation of the solvent, methanol. The O-methylation reaction preceding the methoxylation was advantageous from the point of view of separation, purification, and isolation of the desired product and also in reducing the tar formation. The residue obtained was minimized to 0.6-0.7 wt % of the DBMT. The methoxylation reaction with distillative removal of methanol gave a conversion of 98% of DBMT to the mixture of methoxylated products, and the conversion to TMT was 86.5% as compared to 93% and 70.81%, respectively, when the reaction was carried out under pressure in a sealed reactor. However, the overall conversion to TMT based on p-cresol is 64.27% for the methoxylation reaction under pressure and 78.46% for the reaction by continuous removal of methanol calculated as isolated yield. The advantages of the methoxylation of the DBMT over the published literature procedures involving direct methoxylation of 3,5-dibromo-p-cresol followed by methylation of the dimethoxy-p-cresol are the ease of separation, purification, and isolation by vacuum fractionation of the desired product TMT.
Sankaranarayanan, Ananthakrishnan,Chandalia
p. 487 - 492
(2012/12/22)

Efficient chemoselective alcohol oxidation using oxygen as oxidant. Superior performance of gold over palladium catalysts
Gold nanoparticles supported on nanocrystalline ceria (Au/CeO2) is a general, air- and moisture-stable, commercial catalyst for the atmospheric pressure, solventless oxidation of aromatic, primary and secondary alcohols to the corresponding benzaldehyde or ketone compound. Aliphatic primary alcohols are oxidized to the corresponding alkyl ester and aliphatic secondary alcohols are oxidized to ketones. Conversions and product yields are in most of the cases excellent. The oxidizing reagent and the experimental conditions are almost ideal from the environmental point of view. Comparison with analogous ceria supported and hydroxyapatite-supported palladium catalysts, Au/CeO2 clearly shows the superior performance of Au/CeO2 in terms of higher chemoselectivity. In contrast to palladium catalysts that promote C{double bond, long}C double isomerization, Au/CeO2 oxidizes selectively allylic alcohols to conjugated ketones.
Abad, Alberto,Almela, Carles,Corma, Avelino,García, Hermenegildo
p. 6666 - 6672
(2007/10/03)

Pd/C-Catalyzed Transfer-Hydrogenation of Benzaldehydes to Benzyl Alcohols Using Potassium Formate as the Selective Hydrogen Donor
Aromatic and aliphatic aldehydes are selectively reduced to primary alcohols under mild conditions with potassium formate in the presence of Pd/C catalyst. The high selectivity obtained is attributed due to the presence of the basic potassium bicarbonate generated in situ from the formate salt via the hydrogen transfer process. Molecular hydrogen shows similar activity in the presence of potassium carbonate salts. Ketones did not react under these conditions; therefore, this method is used to separate aldehydes selectively from a mixture of aldehydes and ketones.
Baidossi, Mubeen,Joshi, Ashutosh V.,Mukhopadhyay, Sudip,Sasson, Yoel
p. 643 - 650
(2007/10/03)

Should anionised benzylic sulfones be considered as carbenoids?
Na·Hg reduction of benzyl sulfones 1c-e in aprotic solvent conditions affords stilbenes 4c-e, an olefination process best explained by assuming that the corresponding sulfone carbanion, which was formed under these conditions, is decomposed into a carbene species.
Jolivet,Uguen
p. 7907 - 7911
(2007/10/03)

Laser versus lamp photolysis: A comparative account of the photolysis of papavarine by laser and UV lamp
Papavarine, when irradiated by N2 laser and UV lamp separately, gives different products. The time required is less and yields obtained are high under laser irradiation.
Chawada, Shivraj Singh,Bokadia,Jain, Shubha
p. 865 - 867
(2007/10/03)

Method for the conversion of 3- and 4-methylcatechol to benzaldehyde
The 3- and 4-methylcatechols are converted to the corresponding benzaldehyde by first alkylating the hydroxyl groups to form an alkylated methylcatechol. The methyl group is then converted to a methyl dibromide group using 1,3-dibromo-5,5-dimethylhydantoin in the presence of a non-polar, non-reactive solvent such as carbon tetrachloride and heptane and a radical initiator having a ten hour half-life temperature in the range of 47 DEG to 55 DEG C. The dibromide is then hydrolyzed to form the aldehyde.
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(2008/06/13)

Aryl radical cyclizations of 1-(2′-bromobenzyl)isoquinolines with AIBN-Bu3SnH: Formation of aporphines and indolo[2,1-a]isoquinolines
(matrix presented) Radical cyclization of alkoxy-substituted 1-(2′-bromobenzyl)-3,4-dihydroisoquinolines 1 with AIBN-Bu3SnH gave 6a,7-dehydroaporphines 2 preferentially. A steric repulsion between the respective alkoxy groups at the 7- and 3′-positions gave 5,6-dihydroindolo[2,1-a]isoquinolines 3 in a disfavored 5-endo cyclization mode. Radical cyclizations of the related substrates, such as 1-(2′-bromobenzoyl)isoquinolines or 1-(2′-bromo-α-hydroxybenzyl)isoquinolines, were also found to give the corresponding oxoaporphines or oxyaporphines.
Orito, Kazuhiko,Uchiito, Shiho,Satoh, Yoshitaka,Tatsuzawa, Takashi,Harada, Rika,Tokuda, Masao
p. 307 - 310
(2007/10/03)

Chemoselective O-methylation of phenols under non-aqueous condition
Chemoselective O-methylation of substituted phenols takes place in dry. tetrahydrofuran (THF) in the presence of LiOH.H2O and dimethylsulfate (DMS). Quantitative methyl transfer from DMS preserves the atom economy.
Basak, Anindita,Nayak, Mrinal K.,Chakraborti, Asit K.
p. 4883 - 4886
(2007/10/03)

Studies on Rubia akane (RA) derivatives. Part 8. Design, syntheses and antitumour activity of cyclic hexapeptide RA analogues possessing an alkyl substituent on the Tyr-3 aromatic ring
The effective conversion of RA-VII 1 into the naturally less-accessible RA-II 4 has been devised through boron tribromide bis-O-demethylation and successive selective partial O-methylation using diazo(trimethylsilyl)methane. The O-triflate 11 prepared from RA-II 4 was subjected to cross-coupling reaction with alkylstannanes to produce analogues 12, 13 and 15, while compounds 13 and 15 were later converted into analogues 14 and 16, respectively. Analogues 12-16 showed antitumour activity against P-388 leukaemia both in vitro and in vivo.
Hitotsuyanagi, Yukio,Lee, Suguru,Ito, Izumi,Kondo, Kazuyuki,Takeya, Koichi,Yamagishi, Takehiro,Nagate, Takatoshi,Itokawa, Hideji
p. 213 - 217
(2007/10/03)

Reactivity in cleavage of dimethoxybenzenes by sodium in liquid ammonia
The sodium/liquid ammonia cleavage of the dimethoxybenzenes and related substances, reported in large part by Birch in 1947, has been re-examined with use of improved techniques. Remarkable patterns of reactivity (e.g., ortho > meta ? para) that he described are confirmed and extended. They are agreeably rationalized by means of a simple, approximate adaptation from MO theory.
Bunnett, Joseph F.,Jenvey, Judy
p. 8069 - 8073
(2007/10/03)

The Photochemistry of Methoxy-Substituted Benzyl Acetates and Benzyl Pivalates: Homolytic vs Heterolytic Cleavage
The multiple methoxy-substituted benzyl acetates (3g-i) and benzyl pivalates (4g-i) have been photolyzed in methanol solution.The products of these reactions are derived from two critical intermediates; the benzyl radical/acyloxy radical pair and the benzyl cation/carboxylate anion pair.As predicted by the meta effect, the yield of ion-derived product, the methyl ether in this case, was enhanced by the presence of the m-methoxy groups.The yield of ether, for the acetate esters, varied from 2percent for the 4-methoxy-substituted ester to 66percent for the 3,4,5-trimethoxy-substituted ester.In contrast, the yield of ether, for the pivalate esters, varied from 1percent for the 4-methoxy-substituted ester to 20percent for the 3,4,5-trimethoxy-substituted one.The meta effect does not explain these differences; electron transfer converting the radical pair to the ion pair is still an important pathway in the mechanism for ion formation.A quantitative analysis of the yield of the ethers was done in order to obtain the electron-transfer rate constants.This analysis revealed that the yield of the ethers was higher than expected based on previous results for other substituted benzyl acetates.A possible explanation for this discrepancy is that internal return of the radical pair to starting material for the acetate esters is more efficient than for the pivalate esters.Also, the esters 3k and 3l, were prepared to study the effect of electron-withdrawing groups in the meta position.For these esters, the benzylic cleavage reactions were inefficient and an isomerization reaction, the benzvalene rearrangement, was competitive.
Pincock, J. A.,Wedge, P. J.
p. 5587 - 5595
(2007/10/02)

Rearrangement of (Polymethoxybenzyl)ammonium N-Methylides
Reaction of N,N-dimethyl-N-(polymethoxy-substituted benzyl)ammonium iodides 1a-e with cesium fluoride gave polymethoxy-substituted 5--6-methylene-1,3-cyclohexadienes 3 and 5 ( sigmatropic rearrangement products).However, these were quickly hydrolyzed to polymethoxytoluenes 8 during the aqueous workup.The pathway of the hydrolysis of 3 and 5 is discussed.
Maeda, Yasuhiro,Shirai, Naohiro,Sato, Yoshiro,Tatewaki, Hiroshi
p. 7897 - 7901
(2007/10/02)

An efficient desulfonylation method mediated by magnesium in ethanol
An extremely convenient desulfonation method of primary, secondary, tertiary alkyl and vinyl phenyl sulfones was developed by using magnesium in ethanol in the presence of catalytic amount of mercuric chloride to give the corresponding alkanes and alkene in almost quantitative yields.
Lee,Choi,Lee,Pak
p. 4541 - 4542
(2007/10/02)

Correlation of Reaction Rates with a Substituent Constant Scale Derived from Calculated Electron Densities for a Computer Control Algorithm
A new ? substituent scale based on electron density calculations by the AM1 quantum mechanical model has been established and used to correlate rates of O-methylation of substituted phenols, as part of a chemical artificial intelligence to control a fully automated apparatus for methyl iodide labeling.
Cork, David G.,Hayashi, Nobuyoshi
p. 1583 - 1585
(2007/10/02)

Syntheses of Antibacterial 2,4-Diamino-5-benzylpyrimidines. Ormetoprim and Trimethoprim
A general and mild method for the synthesis of 2,4-diamino-5-benzylpyrimidines was achieved by the Friedel-Crafts reaction between 2-(methoxymethylene)-3-methoxypropanenitrile (10) and an activated aromatic substrate followed by treatment with guanidine.The method is illustrated by a synthesis of ormetoprim (2) in 75percent overall yield from 3,4-dimethoxytoluene (12).Efficient syntheses of trimethoprim (1) and 2 were also accomplished via prior base-catalyzed 1,3-prototropic isomerization of cinnamonitriles 19 and 20, respectively, followed by condensation with guanidine. 12 was prepared from 3-bromo-4-methoxytoluene by a Cu(I)-catalyzed displacement of bromine by methoxide and 4,5-dimethoxy-2-methylbenzaldehyde was obtained from 12 in 87percent yield by a pyridine-catalyzed Vilsmeier reaction using DMF-POCl3.
Manchand, Percy S.,Rosen, Perry,Belica, Peter S.,Oliva, Gloria V.,Perrotta, Agostino V.,Wong, Harry S.
p. 3531 - 3535
(2007/10/02)

Fragmentation of Laudanosine by Single Electron Transfer Reactions
The radical cation of laudanosine, formed by a photoinduced electron transfer reaction or by oxidation with a tris(4-bromophenyl)aminium salt, undergoes cleavage of a C-C bond similar to the mass spectrometric fragmentation induced by electron ionization.
Yamada, Shuzo,Tanaka, Tsuyoshi,Akiyama, Shinichi,Ohashi, Mamoru
p. 449 - 450
(2007/10/02)

Reduction of Monobenzylic Alcohols with Sodium Borohydride/Trifluoroacetic Acid
Sodium borohydride/trifluoroacetic acid readily effects the reduction of monobenzylic alcohols to afford the corresponding hydrocarbons in moderate to high yields.
Nutaitis, Charles F.,Bernardo, Joseph E.
p. 487 - 493
(2007/10/02)

Analysis of dimethoxybenzyl chloride by gas-liquid chromatography with in situ reaction
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Marek,Kochetova,Rotter
p. 261 - 265
(2007/10/02)

Ethyl(or methyl) 4-acetoxy(or propionyloxy)-5,6,7 or 8-di(or tri-)substituted-2-naphthoates
Novel antiviral ring-substituted ethyl or methyl 4-acetoxy (or propionyloxy)-2-naphthoates are provided.
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(2008/06/13)

REDUCTION WITH METAL BOROHYDRIDE-TRANSITION METAL SALT SYSTEM. II. REDUCTION OF BENZYL ACETATES TO HYDROCARBONS WITH SODIUM BOROHYDRIDE-NICKEL(II) CHLORIDE
Reductive cleavage of benzyl acetates selectively with nickel boride yielding corresponding hydrocarbons is described.
He, Yun,Pan, Xinfu,Zhao, He,Wang, Shaofei
p. 3051 - 3054
(2007/10/02)