- Zirconium and hafnium polyhedral oligosilsesquioxane complexes-green homogeneous catalysts in the formation of bio-derived ethers: Via a MPV/etherification reaction cascade
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The polyhedral oligosilsesquioxane complexes, {[(isobutyl)7Si7O12]ZrOPri·(HOPri)}2 (I), {[(cyclohexyl)7Si7O12]ZrOPri·(HOPri)}2 (II), {[(isobutyl)7Si7O12]HfOPri·(HOPri)}2 (III) and {[(cyclohexyl)7Si7O12]HfOPri·(HOPri)}2 (IV), were synthesized in good yields from the reactions of M(OPri)4 (M = Zr, Hf) with R-POSS(OH)3 (R = isobutyl, cyclohexyl), resp. I-IV were characterized by 1H, 13C and 29Si NMR spectroscopy and their dimeric solid-state structures were confirmed by X-ray analysis. I-IV catalyze the reductive etherification of 2-hydroxy- and 4-hydroxy and 2-methoxy and 4-methoxybenzaldehyde and vanillin to their respective isopropyl ethers in isopropanol as a "green"solvent and reagent. I-IV are durable and robust homogeneous catalysts operating at temperatures of 100-160 °C for days without significant loss of catalytic activity. Likewise, I-IV selectively catalyze the conversion of 5-hydroxymethylfurfural (HMF) into 2,5-bis(isopropoxymethyl)furane (BPMF), a potentially high-performance fuel additive. Similar results were achieved by using a combination of M(OPri)4 and ligand R-POSS(OH)3 as a catalyst system demonstrating the potential of this "in situ"approach for applications in biomass transformations. A tentative reaction mechanism for the reductive etherification of aldehydes catalysed by I-IV is proposed. This journal is
- Garg, Shipra,Unruh, Daniel K.,Krempner, Clemens
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p. 211 - 218
(2021/01/28)
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- Uranyl(VI) Triflate as Catalyst for the Meerwein-Ponndorf-Verley Reaction
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Catalytic transformation of oxygenated compounds is challenging in f-element chemistry due to the high oxophilicity of the f-block metals. We report here the first Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl substrates with uranium-based catalysts, in particular from a series of uranyl(VI) compounds where [UO2(OTf)2] (1) displays the greatest efficiency (OTf = trifluoromethanesulfonate). [UO2(OTf)2] reduces a series of aromatic and aliphatic aldehydes and ketones into their corresponding alcohols with moderate to excellent yields, using iPrOH as a solvent and a reductant. The reaction proceeds under mild conditions (80 °C) with an optimized catalytic charge of 2.3 mol % and KOiPr as a cocatalyst. The reduction of aldehydes (1-10 h) is faster than that of ketones (>15 h). NMR investigations clearly evidence the formation of hemiacetal intermediates with aldehydes, while they are not formed with ketones.
- Kobylarski, Marie,Monsigny, Louis,Thuéry, Pierre,Berthet, Jean-Claude,Cantat, Thibault
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supporting information
p. 16140 - 16148
(2021/11/01)
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- Iodine-catalyzed transformation of aryl-substituted alcohols under solvent-free and highly concentrated reaction conditions
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Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols. The relative reactivity of substituted 1-phenylethanols in I2-catalyzed dimerization under SFRC provided a good Hammett plot ρ+ = -2.8 (r2 = 0.98), suggesting the presence of electron-deficient intermediates with a certain degree of developed charge in the rate-determining step.
- Jereb, Marjan,Vra?i?, Dejan
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p. 747 - 762
(2018/01/17)
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- A synthetic method of the compound animal pen ether class
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The invention relates to a synthetic method of a benzyl ether compound. The synthetic method is used for avoiding environmental pollution caused by conventional benzyl ether compound synthetic methods. The synthetic method comprises following steps: step 1, a benzyl silane compound, an oxidizing agent, and a light reaction catalyst are delivered into a reactor, the reactor is vacuumized, and is filled with nitrogen for protection, an alkali compound and an alcohol reagent are delivered into the reactor through syringes, the reactor is exposed to visible light, reaction is carried out at room temperature with magnetic stirring, after reaction, an obtained reaction solution is filtered, and a liquid obtained via filtration is subjected to condensation so as to remove solvents and obtain a concentrated solution; and step 2, the concentrated solution is subjected to silica-gel column chromatography for separation and purification so as to obtain the benzyl ether compound, wherein a mixed solution of petroleum ether and ethyl acetate is taken as an eluent. Reaction conditions are mild; operation is simple and convenient; reaction yield is high; and the maximum reaction yield can be 93%.
- -
-
Paragraph 0075; 0076; 0077; 0078; 0079-0086
(2017/04/27)
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- Auto-Tandem Catalysis with Frustrated Lewis Pairs for Reductive Etherification of Aldehydes and Ketones
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Herein we report that a single frustrated Lewis pair (FLP) catalyst can promote the reductive etherification of aldehydes and ketones. The reaction does not require an exogenous acid catalyst, but the combined action of FLP on H2, R-OH or H2O generates the required Br?nsted acid in a reversible, “turn on” manner. The method is not only a complementary metal-free reductive etherification, but also a niche procedure for ethers that would be either synthetically inconvenient or even intractable to access by alternative synthetic protocols.
- Bakos, Mária,Gy?m?re, ádám,Domján, Attila,Soós, Tibor
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supporting information
p. 5217 - 5221
(2017/04/27)
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- Direct synthesis of ethers from aldehydes and ketones. One-pot reductive etherification of benzaldehydes, alkyl aryl ketones, and benzophenones
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Benzyl alcohols formed by the reduction of benzaldehydes, alkyl aryl ketones, and benzophenones with sodium tetrahydridoborate in alcohols undergo in situ etherification with the solvent in the presence of a catalytic amount of HCl. Thus the process may be regarded as one-pot transformation of carbonyl compounds into the corresponding benzyl ethers. The yields of ethers depend on the substituent nature in the aromatic fragment of the initial carbonyl compound and on the alcohol used as reduction medium.
- Mochalov,Fedotov,Trofimova,Zefirov
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p. 503 - 512
(2016/06/13)
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- Sulfated tungstate as hydroxyl group activator for preparation of benzyl, including p-methoxybenzyl ethers of alcohols and phenols
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Sulfated tungstate was found to be an effective heterogeneous and reusable catalyst for hydroxy group activation–mediated preparation of benzylic ethers including p-methoxybenzylic ethers of a wide range of alcohols and phenols under mild reaction conditions.
- Katkar, Kamlesh V.,Veer, Sachin D.,Akamanchi, Krishnacharya G.
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supporting information
p. 1893 - 1901
(2016/11/25)
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- Chemoselective formation of unsymmetrically substituted ethers from catalytic reductive coupling of aldehydes and ketones with alcohols in aqueous solution
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A well-defined cationic Ru-H complex catalyzes reductive etherification of aldehydes and ketones with alcohols. The catalytic method employs environmentally benign water as the solvent and cheaply available molecular hydrogen as the reducing agent to afford unsymmetrical ethers in a highly chemoselective manner.
- Kalutharage, Nishantha,Yi, Chae S.
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supporting information
p. 1778 - 1781
(2015/04/14)
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- Proton-exchanged montmorillonite-mediated reactions of methoxybenzyl esters and ethers
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Proton-exchanged montmorillonite (H-mont) was found to be an eco-friendly and cost-effective catalyst for the generation of O-methylated quinone methides (QM) from the corresponding p or o-methoxybenzyl esters and ethers. Nucleophilic trapping of the O-methylated QM with arenes, alcohols, 1,3-dicarbonyl compounds, silyl enol ethers, and allylsilanes has been carried out, respectively, leading to eco-friendly benzylation reactions. Using this protocol, H-mont-mediated deprotection of PMB-protected esters and ethers have been realized for the first time. This work would pave the way for further exploration in O-alkylated QM that are of chemical and biological significance.
- Chen, Dongyin,Xu, Chang,Deng, Jie,Jiang, Chunhuan,Wen, Xiaoan,Kong, Lingyi,Zhang, Ji,Sun, Hongbin
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p. 1975 - 1983
(2014/03/21)
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- A very practical and selective method for PMB protection of alcohols
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A very simple, practical and efficient one-step heterogeneous protocol for the PMB protection of alcohols using Amberlyst-15 has been developed. The stability and hazard issues regarding PMBCl and PMBBr are totally avoided by directly using anisyl alcohol for the protection. Alcohols are protected in very good yields. The selective mono-PMB protection of diols as well as di-PMB protection of diols was achieved in good yields, along with the demonstration of recyclability of the catalyst.
- Chavan, Subhash P.,Harale, Kishor R.
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experimental part
p. 4683 - 4686
(2012/09/05)
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- New method for the synthesis of benzyl alkyl ethers mediated by FeSO 4
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The synthesis of benzyl alkyl ethers from benzyl bromides and alcohols using FeSO4 as a recoverable and reusable mediator has been described without use of base and cosolvent under mild conditions.
- Joshi, Girdhar,Adimurthy, Subbarayappa
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experimental part
p. 720 - 728
(2011/03/22)
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- A simple and an efficient indium trichloride catalyzed benzyl etherification
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An efficient method has been developed for the synthesis of benzyl ethers of alkyl, allyl and propargyl alchols by simple, direct coupling of alcohols in the presence of catalytic amount of L1C13 under solvent-free condition.
- Bhaskar,Solomon,Babu,Muralidharan,Perumal, Paramasivan T.
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scheme or table
p. 795 - 801
(2011/01/04)
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- Bifunctional copper catalysts for an atom efficient ether synthesis
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A direct etherification of aromatic ketones and aliphatic alcohols into the corresponding asymmetrical ethers by the use of a bifunctional heterogeneous copper catalyst is described. The reaction protocol reveals to be versatile and convenient respect to the traditional ether synthesis for both environmental and practical concerns.
- Zaccheria, Federica,Psaro, Rinaldo,Ravasio, Nicoletta
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experimental part
p. 5221 - 5224
(2009/12/06)
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- A novel, chemoselective and efficient microwave-assisted deprotection of silyl ethers with Selectfluor
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A novel microwave-assisted, chemoselective and efficient method for the cleavage of silyl ethers (aliphatic and aromatic) catalyzed by Selectfluor is reported. A wide range of TBS-, TIPS-, and TBDPS-protected alkyl silyl ethers can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The chemoselective deprotection of phenolic TBS ethers, and not the TIPS- or TBDPS-protected phenolic ethers, and the deprotection of silyl esters were also achieved under these reaction conditions. In addition, the transetherification and etherification of benzylic hydroxy groups in alcoholic solvents is observed.
- Shah, Syed Tasadaque A.,Singh, Surendra,Guiry, Patrick J.
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experimental part
p. 2179 - 2182
(2009/07/01)
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- Water compatible gold(III)-catalysed synthesis of unsymmetrical ethers from alcohols
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An efficient and broad-scoped method for the preparation of unsymmetrical ethers from alcohols catalysed by the simplest and least expensive gold catalyst, NaAuCl4, is described for the first time. The procedure enables the etherification of benzylic and tertiary alcohols with moderate to good yields under mild conditions with low catalyst loading. Symmetrical ethers, the usual side products in the etherification of alcohols, were not detected in this case. The formation of the racemic ether from a chiral benzyl alcohol suggests the intermediacy of a carbocation, which has not previously been postulated for gold-catalysed reactions involving alcohols.
- Cuenca, Ana B.,Mancha, Gisela,Asensio, Gregorio,Medio-Simon, Mercedes
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experimental part
p. 1518 - 1523
(2009/04/04)
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- An efficient and highly selective deprotecting method for β-(trimethylsilyl)ethoxymethyl ethers
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A series of β-(trimethylsilyl)ethoxymethyl ethers were hydrolyzed to their corresponding alcohols in high yields by using a catalytic amount of CBr4 (15%) in MeOH under refluxing reaction conditions. The chemoselective deprotection between trialkylsilyl and β-(trimethylsilyl)-ethoxymethyl-protected alcohols can be achieved by using an alcohol with steric hindrance such as iPrOH. The selectivity also can be achieved in the CBr4/MeOH reaction mixture under ultrasonic reaction conditions.
- Chen, Ming-Yi,Lee, Adam Shih-Yuan
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p. 1384 - 1387
(2007/10/03)
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- Oxidation of benzylsilanes and benzyltins by oxovanadium(V) compound and molecular oxygen
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Benzylsilane and benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketones) and/or carboxylic acids. In the reaction of benzyltins, oxovanadium(V) compound can be reduce
- Hirao, Toshikazu,Morimoto, Chihiro,Takada, Takashi,Sakurai, Hidehiro
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p. 5073 - 5079
(2007/10/03)
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- THE EFFECT OF ARYL SUBSTITUENTS ON ARYLCARBENE REACTIVITY
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Substituted (p-MeO, p-Me, H, p-Cl, p-Br, m-Br, m-MeO, 3,4-Cl2, p-CO2Me, m-CN and p-CN) monophenylcarbenes are generated in a binary mixture of substrates (methanol, cis-4-methyl-2-pentene and cyclohexane) and the relative rate of O - H insertion into methanol to stereospecific cyclopropanation of the olefin to C - H insertion into cyclohexane are calculated from the ratios of products and substrates.It is found (i) that the reactivities of the substrates decrease in the order of methanol, olefin and cyclohexane and (ii) that electron-donating substituents generally lead to reaction with the more reactive substrates while the reaction with the less reactive substrates is favoured in the case of electron-withdrawing substituents.These results are interpreted in terms of the change in the electrophilicity of the singlet arylcarbene by the substituents rather than the change in the singlet-triplet equilibrium.
- Tomioka, Hideo,Tabayashi, Kazuo,Ozaki, Yasuji,Izawa, Yasuji
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p. 1435 - 1440
(2007/10/02)
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- Effects of Substituents and Generation Methods on Insertion-Addition Selectivities of ''Arylcarbene'' in Alcohol-Olefin Binary Mixtures. Intervention of Reaction of Diazo Compounds Masquerading as Carbenes
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A Hammett study of the insertion-addition selectivity (Ki/ka) and cyclopropanation stereoselectivity (kc/kt) of "arylcarbene" generated either photolytically or thermally in 2-propanol-ethyl vinyl ether binary mixtures showed that ρ values are highly sensitive to the generation method.Thus, plots of ki/ka and kc/kt vs. ? (?+) in the photolytic run gave ρ values of -0.96 (r = -0.96) and -0.15 (r = -0.95), respectively, whereas similar values are +1.4 (r = 0.93) and -1.1 (r = -0.96) in the thermal run.The results along with the effects of precursor, temperature, and sensitizer on the product distributions are interpreted as indicating that, while free carbene is involved in the photolytic run, the ground-state diazo compound is masquerading as carbene in its thermal reaction with the olefin.
- Tomioka, Hideo,Suzuki, Shinji,Izawa, Yasuji
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p. 1047 - 1050
(2007/10/02)
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- Temperature and Substituent Effects on Regioselectivity in the Insertion of Arylcarbene into Alcohols
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Photolysis of aryldiazomethanes in methanol, ethanol, and 2-propanol gave OH insertion products along with small amounts of CH insertion products at ambient temperature.However, the CH insertion products increased significantly at the expense of the ether as the temperature was lowered.The attempted sensitized decomposition of the diazomethane did not lead to an increase in the CH insertion products presumably because of a rapid singlet-triplet equilibrium.The key intermediate leading to the CH insertion is suggested to be ground-state triplet arylcarbene, based on the accumulated spectroscopic as well as chemical evidence for the intervention of the triplet arylcarbene in the low-temperature photolysis of aryldiazomethanes.Substituents on the phenyl ring also have an appreciable effect on the insertion selectivity.At room temperature, the OH/CH insertion selectivity increased with the electron-donating ability of the substituents.This is interpreted in terms of the substituent effect on the transition state of OH insertion, where there is a deficiency of electrons at the benzylic carbon atom, rather than on the stability of singlet carbene.At low temperature, both electron-donating and -withdrawing substituents facilitate OH insertion, indicating the change in substituents induces a concomitant change in the insertion mechanism, presumably due to decreasing nucleophilicity of carbene with increasing electron-withdrawing ability as well as decreasing proton-donor activity of alcohol with decreasing temperature.This may also reflect the effect of the substituent on the singlet-triplet energy gap.
- Tomioka, Hideo,Suzuki, Shinji,Izawa, Yasuji
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p. 3156 - 3162
(2007/10/02)
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