- Aromatic ether compound or the sulfhydryl compound
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[Problem] Aromatic ether compounds and aromatic sulfide compound of this new technology to[Solution] In general formula (1a), (1b), (1c) palladium or nickel compound or a phosphine compound represented by the compound comprising a transition metal compound in the presence of a transition metal catalyst, (A1) is represented by compounds having hydroxy carbon C a-OH or (A2) with a compound represented by the sulfhydryl carbon C a-SH, nitro group (- NO2 ) To react with an aromatic nitro compound (B), (A1) to the compound of the aromatic nitro compound (C1) or the reaction product of an aromatic ether compounds (B) hetero coupling (A2) of the compounds of the reaction product of an aromatic sulfide compound of an aromatic nitro compound (C2) generating (B) hetero coupling characterized by comprising the step of, aromatic ether compounds or aromatic sulfide compound. [Drawing] no
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Paragraph 0072; 0074; 0079; 0109
(2021/11/19)
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- Transition-Metal-Free and Base-Promoted Carbon-Heteroatom Bond Formation via C-N Cleavage of Benzyl Ammonium Salts
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A facile and general method for constructing carbon-heteroatom (C-P, C-O, C-S, and C-N) bonds via C-N cleavage of benzyl ammonium salts under transition-metal-free conditions was reported. The combination of t-BuOK and 18-crown-6 enabled a wide range of substituted benzyl ammonium salts to couple readily with different kinds of heteroatom nucleophiles, i.e. hydrogen phosphoryl compounds, alcohols, thiols, and amines. Good functional group tolerance was demonstrated. The scale-up reaction and one-pot synthesis were also successfully performed.
- Liu, Long,Tang, Yuanyuan,Wang, Kunyu,Huang, Tianzeng,Chen, Tieqiao
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p. 4159 - 4170
(2021/03/09)
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- Oxalohydrazide Ligands for Copper-Catalyzed C?O Coupling Reactions with High Turnover Numbers
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Here, we report a class of ligands based on oxalohydrazide cores and N-amino pyrrole and N-amino indole units that generates long-lived copper catalysts for couplings that form the C?O bonds in biaryl ethers. These Cu-catalyzed coupling of phenols with aryl bromides occurred with turnovers up to 8000, a value which is nearly two orders of magnitude higher than those of prior couplings to form biaryl ethers and nearly an order of magnitude higher than those of any prior copper-catalyzed coupling of aryl bromides and chlorides. This ligand also led to copper systems that catalyze the coupling of aryl chlorides with phenols and the coupling of aryl bromides and iodides with primary benzylic and aliphatic alcohols. A wide variety of functional groups including nitriles, halides, ethers, ketones, amines, esters, amides, vinylarenes, alcohols and boronic acid esters were tolerated, and reactions occurred with aryl bromides in pharmaceutically related structures.
- Ray, Ritwika,Hartwig, John F.
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supporting information
p. 8203 - 8211
(2021/03/08)
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- α-Lithiobenzyloxy as a Directed Metalation Group in ortho-Lithiation Reactions
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The α-lithiobenzyloxy group, easily generated from aryl benzyl ethers by selective α-lithiation with t-BuLi at low temperature, behaves as a directed metalation group (DMG) providing a direct access to o-lithiophenyl α-lithiobenzyl ethers. This ortho-directing effect is reinforced in substrates bearing an additional methoxy group at the meta position. The generated dianions can be reacted with a selection of electrophiles including carboxylic esters and dihalosilanes or germanes, which afford interesting benzofuran, sila(germa)dihydrobenzofuran, and silachroman derivatives from simple aryl benzyl ethers.
- Sedano, Carlos,Velasco, Rocío,Feberero, Claudia,Suárez-Pantiga, Samuel,Sanz, Roberto
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supporting information
p. 6365 - 6369
(2020/08/24)
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- Oxalic Diamides and tert-Butoxide: Two Types of Ligands Enabling Practical Access to Alkyl Aryl Ethers via Cu-Catalyzed Coupling Reaction
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A robust and practical protocol for preparing alkyl aryl ethers has been developed, which relies on using two types of ligands to promote Cu-catalyzed alkoxylation of (hetero)aryl halides. The reaction scope is very general for a variety of coupling partners, particularly for challenging secondary alcohols and (hetero)aryl chlorides. In case of coupling with aryl chlorides and bromides, two oxalic diamides serve as the powerful ligands. The tert-butoxide is first demonstrated as a ligand for Cu-catalyzed coupling reaction, leading to alkoxylation of aryl iodides complete at room temperature. Additionally, a number of carbohydrate derivatives are applicable for this coupling reaction, affording the corresponding carbohydrate-aryl ethers in 29-98% yields.
- Chen, Zhixiang,Jiang, Yongwen,Zhang, Li,Guo, Yinlong,Ma, Dawei
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supporting information
p. 3541 - 3549
(2019/02/26)
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- BIS-BENZIMIDAZOLE COMPOUNDS AND METHODS OF USING SAME
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Provided herein are compounds and methods for modulating abnormal repeat expansions of gene sequences. More particularly, provided are inhibitors of RNA and the uses of such inhibitors in regulating nucleotide repeat expansions, e.g., to treat Myotonic Dystrophy Type 1 (DM1 ), Myotonic Dystrophy Type 2 (DM2), Fuchs dystrophy, Huntington Disease, Amyotrophic Lateral Sclerosis, or Frontotemporal Dementia.
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Paragraph 001142-001144
(2019/06/05)
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- Pd(OAc)2-catalyzed synthesis of benzyl phenyl ether derivatives with H2O2 as an oxidant in neat water
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A new protocol for Pd(OAc)2-catalyzed reactions of different benzyl bromides and various arylboronic acids has been developed to form functionalized benzyl phenyl ethers. This method represents the first instance where arylboronic acid is used as a reaction substrate for benzyl phenyl ether synthesis with H2O2 as the green oxidant under atmospheric oxygen and pure H2O as an environmental friendly solvent without the requirement for phosphine- and N-based ligands, remarkable functional group tolerance, and considerable yield.
- Chen, Qian-Qian,Zhang, Hui-Xian,Yang, Jian-Xin
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p. 115 - 118
(2018/11/10)
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- Metal-Free C-O Bond Functionalization: Catalytic Intramolecular and Intermolecular Benzylation of Arenes
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A catalytic, metal-free intramolecular rearrangement of benzyl phenyl ethers using nitrosonium salt as a catalyst is described. The optimized reaction conditions enabled a catalytic and metal-free Friedel-Crafts alkylation reaction with benzylic alcohols, producing water as the stoichiometric byproduct. A comprehensive scope (>50 examples) for both approaches and application in drug synthesis were demonstrated. Mechanistic studies suggest a Lewis acid-based mechanism for the metal-free Friedel-Crafts reaction.
- Bering, Luis,Jeyakumar, Kirujan,Antonchick, Andrey P.
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supporting information
p. 3911 - 3914
(2018/07/22)
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- Constitutional Isomers of Pentahydroxy-Functionalized Pillar[5]arenes: Synthesis, Characterization, and Crystal Structures
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We herein report the preparation of constitutional isomers of pentahydroxy-functionalized pillar[5]arenes via the deprotection of their benzylated derivatives by catalytic hydrogenation. The structures of the obtained isomers were then established using single crystal X-ray diffraction. We also found that the yield distribution of the different constitutional isomers was dependent on the nature of the substitution, as revealed by HPLC analysis of the crude mixture. Finally, further characterization of the separated constitutional isomers indicated that they possess different melting points, NMR spectra, crystal structures, and stacking patterns in the solid state.
- Al-Azemi, Talal F.,Vinodh, Mickey,Alipour, Fatemeh H.,Mohamod, Abdirahman A.
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p. 10945 - 10952
(2017/10/27)
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- MCM-41-immobilized 1,10-phenanthroline-copper(i) complex: A highly efficient and recyclable catalyst for the coupling of aryl iodides with aliphatic alcohols
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A heterogeneous C-O coupling reaction between aryl iodides and aliphatic alcohols was achieved in neat alcohol or toluene at 110 °C in the presence of 10 mol% of the MCM-41-immobilized 1,10-phenanthroline-copper(i) complex [MCM-41-1,10-phen-CuI] with Cs2CO3 as a base, yielding a variety of aryl alkyl ethers in good to excellent yields. The new heterogeneous copper catalyst can easily be prepared by a simple procedure from commercially available and inexpensive reagents, and recovered by filtration of the reaction solution and recycled at least 8 times without significant loss of activity.
- Lin, Yang,Cai, Mingzhong,Fang, Zhiqiang,Zhao, Hong
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p. 85186 - 85193
(2016/10/12)
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- Exploring the Reactivity of α-Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]-Wittig Rearrangement and the Mechanistic Proposal Revisited
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By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α-lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]-Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α-lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups. The more favored rearrangements are found for substrates with electron-poor aryl groups that favor the anionic pathway.
- Velasco, Rocío,Silva López, Carlos,Nieto Faza, Olalla,Sanz, Roberto
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supporting information
p. 15058 - 15068
(2016/10/11)
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- Copper-catalyzed hydroxylation of aryl halides: Efficient synthesis of phenols, alkyl aryl ethers and benzofuran derivatives in neat water
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A thorough study of environmentally friendly hydroxylation of aryl halides is presented. The best protocol consists of hydroxylation of different aryl bromides and electron-deficient aryl chlorides by water solution of tetrabutylammonium hydroxide catalyzed by Cu2O/4,7-dihydroxy-1,10-phenanthroline. Various phenol derivatives can be obtained in excellent selectivity and great functional group tolerance. This methodology also provides a direct pathway for the formation of alkyl aryl ethers and benzofuran derivatives in a one-pot tandem reaction.
- Wang, Yangxin,Zhou, Chunshan,Wang, Ruihu
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p. 3910 - 3915
(2015/07/15)
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- α-Lithiated Aryl Benzyl Ethers: Inhibition of [1,2]-Wittig Rearrangement and Application to the Synthesis of Benzo[b]furan Derivatives
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The use of t-BuLi at low temperature selectively leads to α-lithiation of benzyl phenyl ether generating a stable organolithium, which can be efficiently trapped with a variety of selected electrophiles prior to suffering the expected [1,2]-Wittig rearrangement. In the case of (o-alkynyl)phenyl benzyl ethers, the intermediate α-aryloxyorganolithium undergoes an unexpected anti intramolecular carbolithiation reaction leading to functionalized benzo[b]furan derivatives.
- Velasco, Rocío,Feberero, Claudia,Sanz, Roberto
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supporting information
p. 4416 - 4419
(2015/09/28)
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- Tetrabutyl ammonium bromide-mediated benzylation of phenols in water under mild condition
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Benzylation of phenol was successfully achieved in water under room temperature mediated by tetrabutylammonium bromide (TBAB) for only 2 h affording the corresponding benzyl phenyl ether with good to excellent yields. This protocol is very efficient, simple, avoiding catalysts, easy to work-up after reaction, and especially 'green'.
- Wang, Hailei,Ma, Yuping,Tian, Heng,Yu, Ajuan,Chang, Junbiao,Wu, Yangjie
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p. 2669 - 2673
(2014/04/03)
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- Choline chloride based deep eutectic solvent as an efficient solvent for the benzylation of phenols
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Deep eutectic solvents (such as the combination of urea and choline chloride) are found to be promising solvent and phase-transfer-media for benzylation of phenol. These methods avoided the complexity of multiple alkylations giving selectively O-alkylated aromatic products. Good to excellent yields of the corresponding benzyl phenyl ether were obtained. The non-toxic, biodegradable, inexpensive, and recyclable nature of DES make this protocol green and cost-effective.
- Singh, Abhilash S.,Shendage, Suresh S.,Nagarkar, Jayashree M.
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p. 7243 - 7246
(2015/02/02)
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- Palladium-catalyzed methoxylation of aromatic chlorides with borate salts
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Herein we disclose a simple palladiumcatalyzed transformation for the methoxylation of aromatic chlorides with tetramethoxyborate salts. The procedure provides a new and efficient synthetic tool for the introduction of a methoxy group into aromatic systems. In addition, the reaction can be achieved using a wide range of aromatic and heteroaromatic chlorides, the cheapest class of halides.
- Tolnai, Gergely L.,Petho, Bálint,Králl, Péter,Nováka, Zoltán
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supporting information
p. 125 - 129
(2014/03/21)
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- NiCl2·6H2O/NaBH4 in methanol: A mild and efficient strategy for chemoselective deallylation/debenzylation of aryl ethers
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Deprotection of allyl/benzyl aryl ethers was achieved chemoselectively. The mild and inexpensive reagent combination of NiCl2·6H 2O/NaBH4 in methanol afforded the products in high yields, within a reaction time of 5-10 min.
- Chouhan, Mangilal,Kumar, Kapil,Sharma, Ratnesh,Grover, Vikas,Nair, Vipin A.
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supporting information
p. 4540 - 4543
(2013/08/23)
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- Copper-catalyzed N- and O-alkylation of amines and phenols using alkylborane reagents
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By the reaction of amines with alkylborane reagents in the presence of a catalytic amount of copper(II) acetate Cu(OAc)2 and di-tert-butyl peroxide, a cross-coupling reaction proceeded and alkylated amines were obtained in good to excellent yields. Phenols are also applicable for this reaction, and the corresponding alkyl aryl ethers were produced.
- Sueki, Shunsuke,Kuninobu, Yoichiro
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supporting information
p. 1544 - 1547
(2013/06/26)
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- Ring-opening reactions of 1,4-diazabicyclo[2.2.2]octane (DABCO) derived quaternary ammonium salts with phenols and related nucleophiles
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1,4-Diazabicyclo[2.2.2]octane (DABCO) has been evaluated as a starting material for the synthesis of 1-alkyl-4-(2-phenoxyethyl)piperazines and related derivatives. We found that 1-alkyl-1,4-diazabicyclo[2.2.2]octan-1-ium salts, resulting from the alkylation of DABCO, efficiently react with a variety of nucleophiles in polyethyleneglycol (PEG) or diglyme at high temperatures to give piperazine products resulting from the nucleophilic ring-opening reaction. The benzylation side reaction was found to be relevant with softer nucleophiles when using 1-benzyl-1,4-diazabicyclo[2.2.2]octan-1-ium salts, while other types of alkylations were not observed. One-pot methodologies allow for the synthesis of piperazines directly from primary alcohols, alkyl halides or sulfonates, using phenols, or other nucleophile sources, and DABCO. The Royal Society of Chemistry 2012.
- Mara, Nenad,Polanc, Slovenko,Koevar, Marijan
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experimental part
p. 1300 - 1310
(2012/03/07)
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- Liquid ammonia as a dipolar aprotic solvent for aliphatic nucleophilic substitution reactions
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The rate constants for the reactions of a variety of nucleophiles reacting with substituted benzyl chlorides in liquid ammonia (LNH3) have been determined. To fully interpret the associated linear free-energy relationships, the ionization constants of phenols ions in liquid ammonia were obtained using UV spectra. These equilibrium constants are the product of those for ion-pair formation and dissociation to the free ions, which can be separated by evaluating the effect of added ammonium ions. There is a linear relationship between the pKa of phenols in liquid ammonia and those in water of slope 1.68. Aminium ions exist in their unprotonated free base form in liquid ammonia and their ionization constants could not be determined by NMR. The rates of solvolysis of substituted benzyl chlorides in liquid ammonia at 25 °C show a Hammett ρ of zero, having little or no dependence upon ring substituents, which is in stark contrast with the hydrolysis rates of substituted benzyl halides in water, which vary 107 fold. The rate of substitution of benzyl chloride by substituted phenoxide ions is first order in the concentration of the nucleophile indicative of a SN2 process, and the dependence of the rate constants on the pKa of the phenol in liquid ammonia generates a Bronsted βnuc = 0.40. Contrary to the solvolysis reaction, the reaction of phenoxide ion with 4-substituted benzyl chlorides gives a Hammett ρ = 1.1, excluding the 4-methoxy derivative, which shows the normal positive deviation. The second order rate constants for the substitution of benzyl chlorides by neutral and anionic amines show a single Bronsted βnuc = 0.21 (based on the aqueous pKa of amine), but their dependence on the substituent in substituted benzyl chlorides varies with a Hammett ρ of 0 for neutral amines, similar to that seen for solvolysis, whereas that for amine anions is 0.93, similar to that seen for phenoxide ion.(Figure Presented)
- Ji, Pengju,Atherton, John,Page, Michael I.
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supporting information; scheme or table
p. 1425 - 1435
(2011/04/23)
-
- Bis(μ-iodo)bis[(-)-sparteine]-dicopper: A versatile catalyst for direct O-Arylation and O-Alkylation of phenols and aliphatic alcohols with haloarenes
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The easy to prepare dimeric bis(μ-iodo)bis[(-)-sparteine]- dicopper ([CuI{(-)-spa}]2 complex) is shown to be versatile catalyst for O-arylation and O-alkylation with various aryl halides with phenols and aliphatic alcohols respectively, including less reactive aryl chlorides, such as chlorobenzene under mild conditions.
- Satyanarayana, Ponnam,Maheswaran, Hariharasarma,Kantam, Mannepalli Lakshmi,Bhargava, Suresh
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supporting information; experimental part
p. 788 - 790
(2011/08/22)
-
- Microwave-assisted methylation of phenols with DMF-DMA
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We evaluated the potential of N,N-dimethylformamide dimethylacetal (DMF-DMA) as a methylating agent for a library of para-substituted phenols under microwave irradiation. The rate of reaction was dictated by the electronic nature of the para-substituent. With an electron-withdrawing group the reaction was completed within 30 min. For electron-donating groups, the reaction times were 60 min. Esterification and enamino-ketone formation was also observed with carboxylic acid and ketone functional groups, respectively.
- Belov, Pavel,Campanella, Veronica L.,Smith, Alison W.,Priefer, Ronny
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experimental part
p. 2776 - 2779
(2011/06/19)
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- C(sp3)-O bond-forming reductive elimination of ethers from bisphosphine-ligated benzylpalladium(II) aryloxide complexes
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On the contrary: Isolated benzylpalladium aryloxide complexes undergo C(sp3)-O bond-forming reductive elimination by a stepwise ionic mechanism (see scheme) distinct from the accepted concerted pathway for reductive elimination of aromatic ethers from arylpalladium(II) species. The mechanism is proposed to result from dissociation of the aryloxide ligand followed by nucleophilic attack on the benzylic carbon atom. Copyright
- Marquard, Seth L.,Hartwig, John F.
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supporting information; experimental part
p. 7119 - 7123
(2011/09/16)
-
- Use of diethoxymethane as a solvent for phase transfer-catalyzed O -alkylation of phenols
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The effectiveness of diethoxymethane (DEM) as a solvent for O-alkylation of a variety of phenols under phase transfer conditions has been examined and evaluated. The reaction between 4-methoxy phenol and benzyl chloride was selected to compare reaction rates in various solvents and the efficiency of various PTCs. This reaction was further studied to develop a commercially amenable process complete with recycle streams and efficient product isolation. DEM is a good solvent for these types of phase transfer-catalyzed reactions and can be considered as an alternative solvent for dichloromethane and toluene.
- Coleman, M. Todd,Leblanc, Gabriel
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experimental part
p. 732 - 736
(2011/07/07)
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- Counterattack mode differential acetylative deprotection of phenylmethyl ethers: Applications to solid phase organic reactions
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A counterattack protocol for differential acetylative cleavage of phenylmethyl ether has been developed. The phenylmethyl moiety is liberated as benzyl bromide that is isolated and reused providing advantages in terms of waste minimization/utilization and atom economy. The applicability of this methodology has been extended for solid phase organic reactions with the feasibility of reuse of the solid support.
- Chakraborti, Asit K.,Chankeshwara, Sunay V.
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supporting information; experimental part
p. 1367 - 1370
(2009/07/04)
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- Synthesis of phenol, aromatic ether, and benzofuran derivatives by copper-catalyzed hydroxylation of aryl halides
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A smooth operator: The copper-catalyzed synthesis of phenols from aryl halides was carried out under relatively mild reaction conditions. Alkyl aryl ethers and benzofurans could also be prepared smoothly by one-pot domino protocols based on hydroxylation of aryl iodides (see scheme).
- Zhao, Dongbing,Wu, Ningjie,Zhang, Shuai,Xi, Peihua,Su, Xiaoyu,Lan, Jingbo,You, Jingsong
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supporting information; experimental part
p. 8729 - 8732
(2010/01/16)
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- Benzyl protection of phenols under neutral conditions: Palladium-catalyzed benzylations of phenols
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Benzyl protection of phenols under neutral conditions was achieved by using a Pd(n3-C3H5)Cp-DPEphos catalyst. The palladium catalyst efficiently converted aryl benzyl carbonates into benzyl-protected phenols through the decarboxylative etherification. Alternatively, the nucleophilic substitution of benzyl methyl carbonates with phenols proceeded In the presence of the catalyst, yielding aryl benzyl ethers.
- Kuwano, Ryoichi,Kusano, Hiroki
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supporting information; experimental part
p. 1979 - 1982
(2009/04/10)
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- N,N-dimethylglycine-promoted ullmann-type coupling reactions of aryl iodides with aliphatic alcohols
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The Ullmann-type coupling reactions of aryl iodides and aliphatic alcohols occur at 110°C with N,N-dimethylglycine as the ligand, giving aryl alkyl ethers in good to excellent yields. Georg Thieme Verlag Stuttgart.
- Zhang, Hui,Ma, Dawei,Cao, Weiguo
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p. 243 - 246
(2007/10/03)
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- Oligomeric benzylsulfonium salts: Facile benzylation via high-load ROMP reagents
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(Chemical Equation Presented) The development of high-load, oligomeric benzylsulfonium salts, generated via ring-opening metathesis polymerization, and their utility in facile benzylations of various nucleophiles is reported. These oligomeric sulfonium salts exist as free-flowing powders and are stable at room temperature. After the benzylation event, purification is attained via simple dry load/filtration, followed by solvent removal to deliver products in excellent yield and purity.
- Zhang, Mianji,Flynn, Daniel L.,Hanson, Paul R.
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p. 3194 - 3198
(2008/02/04)
-
- Practical synthesis of aromatic ethers by SNAr of fluorobenzenes with alkoxides
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Aromatic fluorines have been substituted by alkoxides in a variety of activated and unactivated aromatic systems.
- Rodriguez, Juan R.,Agejas, Javier,Bueno, Ana B.
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p. 5661 - 5663
(2007/10/03)
-
- The synthesis and conformation of oxygenated trianglimine macrocycles
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The synthesis of series of D2h and C2v symmetric oxygenated aromatic dicarboxaldehydes, using dilithiation methodology, is described along with their reactivity in the [3 + 3] cyclocondensation reaction with (1R,2R)-diaminocyclohexane to give oxygenated trianglimine macrocycles. Macrocycles derived from C2v symmetric dialdehydes give macrocycles with a stereogenic aromatic plane with complete diastereocontrol, as a mixture of retainers.
- Kuhnert, Nikolai,Lopez-Periago, Ana,Rossignolo, Giulia M.
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p. 524 - 537
(2007/10/03)
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- Efficient methods for the preparation of alkyl-aryl and symmetrical or unsymmetrical dialkyl ethers between alcohols and phenols or two alcohols by oxidation-reduction condensation
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Oxidation-reduction condensation via alkoxydiphenylphosphines (diphenylphosphinite esters) (1), generated in situ from chlorodiphenylphosphine (2) and alcohols, 2,6-dimethyl-1,4-benzoquinone (3), and phenols proceeds smoothly to afford alkyl-aryl ethers in good to high yields under neutral conditions. In a similar fashion, a new and efficient method for the preparation of symmetrical or unsymmetrical dialkyl ethers in good to high yields is established via tetrafluoro-1,4-benzoquinone (fluoranil) (4), alcohols, and 1 formed in situ from nBuLi-treated alcohols and 2. This method is applicable also to the etherification of chiral secondary or tertiary alcohols with retention or inversion of configurations. The inverted ethers are afforded by treating chiral alkoxydiphenylphosphines and achiral alcohols, while the reaction of achiral alkoxydiphenylphosphines and chiral alcohols forms retained ethers.
- Shintou, Taichi,Mukaiyama, Teruaki
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p. 7359 - 7367
(2007/10/03)
-
- Synergism of low energy microwave irradiation and solid-liquid phase transfer catalysis for selective alkylation of phenols to phenolic ethers
-
A 100% selectivity with an order of magnitude rate enhancement is obtained in the synthesis of phenolic ethers when synergistic combination of solid-liquid phase transfer catalysis and low energy microwave irradiation (MISL-PTC) is employed. As against conventional microwave heating with 600 W power input, the current work demonstrates that a low input of 40 W leads to remarkable enhancement in rates without any destruction of the catalyst.
- Yadav, Ganapati D.,Bisht, Priyal M.
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p. 2885 - 2892
(2007/10/03)
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- Alkylation of phenols by oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone and alkoxydiphenylphosphine
-
Various alkyl phenyl ethers were obtained in high yields by way of oxidation-reduction condensation where alkoxydiphenylphosphine, prepared easily from chlorodiphenylphosphine and corresponding alcohols, was treated with various phenols in the co-existenc
- Shintou, Taichi,Kikuchi, Wataru,Mukaiyama, Teruaki
-
-
- Efficient method for the preparation of carboxylic acid alkyl esters or alkyl phenyl ethers by a new-type of oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone and alkoxydiphenylphosphines
-
A new-type of oxidation-reduction condensation proceeded smoothly to afford carboxylic acid alkyl esters or alkyl phenyl ethers in good to high yields by combined use of alkoxydiphenylphosphines (1) having primary, bulky secondary or tertiary alkoxy groups, a mild quinone-type oxidant such as 2,6-dimethyl-1,4-benzoquinone (DMBQ) and carboxylic acids or phenols. Generally, alkoxydiphenylphosphines were prepared easily from chlorodiphenylphosphine (2) and alcohols in the presence of pyridine, and were isolated by distillation. On the other hand, the phosphines 1 were also prepared in situ from N,N-dimethylaminodiphenylphosphine (3a) and primary or secondary alcohols while primary, bulky secondary or tertiary alkoxydiphenylphosphines were alternatively formed in situ by adding 2 to the "BuLi-treated alcohols in order to perform the above reactions by a one-pot procedure from alcohols and nucleophiles. The reaction of thus formed 1, DMBQ and carboxylic acids or phenols afforded the corresponding alkylated products, including hindered secondary and tertiary alkylated ones, in good to high yields at room temperature. In the case of using chiral secondary alcohols, the corresponding carboxylic acid alkyl esters were obtained as well in high yields with perfect inversion of stereochemistry by SN2 replacement.
- Shintou, Taichi,Kikuchi, Wataru,Mukaiyama, Teruaki
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p. 1645 - 1667
(2007/10/03)
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- Copper-catalyzed coupling of aryl iodides with aliphatic alcohols.
-
[reaction: see text] A simple and mild method for the coupling of aryl iodides and aliphatic alcohols that does not require the use of alkoxide bases is described. The reactions can be performed in neat alcohol. For more precious alcohols, the etherificat
- Wolter, Martina,Nordmann, Gero,Job, Gabriel E,Buchwald, Stephen L
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p. 973 - 976
(2007/10/03)
-
- Oxygen-Carbon bond dissociation enthalpies of benzyl phenyl ethers and anisoles. An example of temperature dependent substituent effects
-
For some time it has been assumed that the direction and magnitude of the effects of Y-substituents on the Z-X bond dissociation enthalpies (BDE's) in compounds of the general formula 4-YC6H4Z-X could be correlated with the polarity of the Z-X bond undergoing homolysis. Recently we have shown by DFT calculations on 4-YC6H4CH2-X (X = H, F, Cl, Br) that the effects of Y on CH2-X BDE's are small and roughly equal for each X, despite large changes in C-X bond polarity. We then proposed that when Y have significant effects on Z-X BDE's it is due to their stabilization or destabilization of the radical. This proposal has been examined by studying 4-YC6H4O-X BDE's for X = H, CH3, and CH2C6H5 both by theory and experiment. The magnitudes of the effects of Y on O-X BDE's were quantified by Hammett type plots of ΔBDE's vs σ+ (Y). Calculations reveal that changes in O-X BDE's induced by changing Y are large and essentially identical (ρ+ = 6.7-6.9 kcal mol-1) for these three classes of compounds. The calculated ρ+ values are close to those obtained experimentally for X = H at ca. 300 K and for X = CH2C6H5 at ca. 550 K. However, early literature reports of the effects of Y on O-X BDE's for X = CH3 with measurements made at ca. 1000 K gave ρ+ ≈ 3 kcal mol-1. We have confirmed some of these earlier, high-temperature O-CH3 BDE's and propose that at 1000 K, conjugating groups such as -OCH3 are essentially free rotors, and no longer lie mainly in the plane of the aromatic ring. As a consequence, the 298 K DFT-calculated ΔBDE for 4-OCH3-anisole of -6.1 kcal mol-1 decreases to -3.8 kcal mol-1 for free rotation, in agreement with the ca. 1000 K experimental value. In contrast, high-temperature O-CH3 ΔBDE's for three anisoles with strongly hindered substituent rotation are essentially identical to those that would be observed at ambient temperatures. We conclude that substituent effects measured at elevated temperatures may differ substantially from those appropriate for 298 K.
- Pratt,De Heer,Mulder,Ingold
-
p. 5518 - 5526
(2007/10/03)
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- Bu3SnH mediated oxidative radical cyclisations: Synthesis of 6H-benzo[c]chromen-6-ones
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Attempts to synthesise 6H-benzo[c]chromen-6-ones by Bu3SnH mediated cyclisation of o-(benzoyl)aryl radicals failed because of the preferred trans conformation of the ester. This problem was overcome by using cyclisation of o-(benzyloxy)aryl and o-[(aryloxy)methyl]aryl radicals to yield 6H-benzo[c]chromenes followed by oxidation to the 6H-benzo[c]chromen-6-ones. 3-Methoxy-6H-benzo[c]chromen-6-one 1, one of the main biologically active constituents of shilajit, a herbal medicine used in countries surrounding the Himalayan mountains, was synthesised using Bu3SnH mediated cyclisation of 1-benzyloxy-2,4-dibromo-5-methoxybenzene 31 to yield 3-methoxy-6H-benzo[c]chromene 25 followed by PCC oxidation of the 6-position. In order to avoid the problems of rearrangement, the aryl radical cyclisation must be designed such that whichever way the spirodienyl intermediate rearranges, the same product is obtained. For instance, the Bu3SnH mediated cyclisation of 1-iodo- and 1-bromo-2-(3-methoxy-phenyloxymethyl)benzenes 22 and 23 respectively gave both the isomers, 1-methoxy-6H-benzo[c]chromenes 24 and 3-methoxy-6H-benzo[c]chromenes 25 via rearrangement of the intermediate spirodienyl radical. The synthesised 6H-benzo[c]chromenes were oxidised in high yield to the corresponding 6H-benzo[c]chromen-6-ones. The mechanism of the 'oxidative' Bu3SnH mediated cyclisation is discussed.
- Bowman, Russell,Mann, Emma,Parr, Jonathan
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p. 2991 - 2999
(2007/10/03)
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- The α-Effect in Benzyl Transfers from Benzylphenylmethyl Sulfonium Salts to N-Methylbenzohydroxamate Anions
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The investigation of the occurrence of the α-effect in group transfers from phenyldialkyl sulfonium ions where one alkyl group is benzyl allows an assay of the effect of changing the nature of the C atom being transferred. The size of the α-effect responds to increasing electron demand, as methyl transfers do. Quantitative relationships between the size of the α-effect are established from both the nucleophilic side and the leaving group side of the SN2 transition state.
- Fountain,Tad-y, Darlene B.,Paul, Timothy W.,Golynskiy, Mikhail V.
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p. 6547 - 6553
(2007/10/03)
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- Polymer-bound triphenylphosphine as traceless reagent for Mitsunobu reactions in combinatorial chemistry: Synthesis of aryl ethers from phenols nad alcohols
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The synthesis of aryl ethers from phenols and alcohols using polymer- bound triphenylphosphine and diethyl azodicarboxylate (DEAD) is described. The polymer-bound triphenylphosphines are easily removed by filtration from the reaction products. This method
- Tunoori, Ashok Rao,Dutta, Dinah,Georg, Gunda I.
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p. 8751 - 8754
(2007/10/03)
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- Isotope effects in nucleophilic substitution reactions X. The effect of changing the nucleophilic atom on ion-pairing in an S(N)2 reaction
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The effect of ion-pairing in an S(N)2 reaction is very different when the nucleophilic atom is changed from sulfur to oxygen, i.e., changing the nucleophile from thiophenoxide ion to phenoxide ion. When the nucleophile is sodium thiophenoxide, ion-pairing markedly alters the secondary α-deuterium kinetic isotope effect (transition state structure) and the substituent effect found by changing the para substituent on the nucleophile. When the nucleophile is sodium phenoxide, ion-pairing does not significantly affect the secondary α-deuterium or the chlorine leaving group kinetic isotope effects (transition state structure) or the substituent effects found by changing a para substituent on the nucleophile or the substrate. The different effects of ion-pairing may occur because the electron density on the hard oxygen atom of the sodium phenoxide is not affected significantly by ion-pairing.
- Fang, Yao-Ren,Lai, Zhu-Gen,Westaway, Kenneth Charles
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p. 758 - 764
(2007/10/03)
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- Highly Efficient and Convenient Methods for the Direct Conversion of Aryl Silyl Ethers and Aryl Acetates into Aryl Alkyl Ethers
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Direct conversion of aryl trialkylsilyl ethers and aryl acetates into the corresponding alkyl-protected phenols such as benzyl and allyl ethers can be conveniently performed by the reaction with alkyl halide in the presence of cesium fluoride and sodium methoxide, respectively, in a one-pot procedure.
- Oriyama, Takeshi,Noda, Kojiro,Yatabe, Kaori
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p. 701 - 703
(2007/10/03)
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- Oxidation potential as a measure of the reactivity of anionic nucleophiles. Behaviour of different classes of nucleophiles
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Anodic peak potentials for 42 anionic nucleophiles are reported along with the rate constants for the reactions of the anions with benzyl chloride.By comparing these rate constants with those of the reactions of outer-sphere electron-transfer reagents (radical anions), it has been demonstrated that the reactions of the anions with benzyl chloride are typical single-step SN2 reactions as opposed to a two-step process comprising dissociative single electron transfer (SET) to benzyl chloride followed by radical combination.The data suggest that very electron-rich nucleophilic anions with potentials of -1.5 to -2.2 V (and more negative) with respect to the ferrocenium/ferrocene couple might participate in a SET reaction.The 42 anions studied included representatives of four classes of nucleophiles, viz. sulfur-, carbon-, oxygen- and nitrogen-centred anions.The previously observed correlation of rate constants and anodic peak potential was again found for these anions with the most reactive species having the most negative peak potentials.Correlations by class indicate that the sensitivity of rate constants to changes in peak potential is greatest (and equivalent) for the sulfur-, carbon- and oxygen-anions and for representatives with the same peak potential, the rate constants by class follow the order sulfur > carbon > oxygen.The nitrogen nucleophiles show a significantly lower sensitivity of rate constant to changes in peak potential than do the other three classes.
- Niyazymbetov, Murat E.,Rongfeng, Zhou,Evans, Dennis H.
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p. 1957 - 1962
(2007/10/03)
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- Facile synthesis of alkyl phenyl ethers using cesium carbonate
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A highly efficient alkylation method of phenols using alkyl halide/cesium carbonate/acetonitrile system is described.
- Lee,Yuk,Cho
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p. 1367 - 1370
(2007/10/02)
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- Novel Synthesis of N,N-Diarylarylmethanamines from N-(Arylmethylene)arenamines and (Arylmethoxy)arenes
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Various N,N-diarylarylmethanamines were synthesized by the reaction of N-(arylmethylene)arenamines with (arylmethoxy)arenes in dimethylformamide solution in the presence of a strong base as a catalyst which is obtained in situ by reacting metallic sodium with this solvent.In general, the reaction may be depicted as the reduction of the imine and addition, on the original imino nitrogen atom, of the aryl group (of the aryloxy moiety) of the ether and presumably oxidation of the arylmethoxy group of the ether to its corresponding aldehyde.Side reactions and a proposed reaction mechanism are discussed.
- Paventi, Martino,Hay, Allan S.
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p. 5875 - 5882
(2007/10/02)
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- The Role of Single-Electron Transfer in SN2-Type Substitution Reactions of Anions with Alkyl Halides
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Rate constants (kobsd) for reactions of electrophiles with: (a) various carbanions, including 9-substituted fluorenide ions (9-GFl-), 9-substituted xanthenide ions, α-cyano carbanions, anb β-diketo enolate ions, (b) phenothiazinide (PTZ-) and carbazole (Cb-) nitranions, (c) 4-substituted phenoxide ions, and (d) thiphenoxide ions, have been campared with rate constants for single-electron transfer (kSET) calculated using a Marcus-type equation.For both 9-GFl- carbanion and 2-GPTZ- nitranion families reacting with SET acceptors, such as 1,1-dinitrocyclohexane, the kobsd/kSET ratio is near unity.For 9-GFl- carbanions reacting with Ph2CHCl the kobsd/kSET ratios range from 2 to 105, those for 2-PTZ- nitranions from 370 to 1.3*104, and those for Cb- nitranions from 108 to 1010.For reactions of 4-GC6H4O- oxanions with Ph2CHCl the ratios range from 103 for G = Me2N to 1013 for G = CN; for PhS- ion reacting with n-BuBr the ratio is 1017.The significance of these results with respect to the role of an outer sphere SET mechanism in substitution reactions of anions with alkyl halides is discussed.
- Bordwell, F.G.,Harrelson, John A.
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p. 4893 - 4898
(2007/10/02)
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- A FACILE AND DIRECT CONVERSION OF ARYL-ACETATE TO ALKYL-ARYL ETHER.
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Arylacetate was directly converted to the corresponding alkyl-aryl ether by treatment with sodium hydride and alkyl halide in THF and HMPA.
- Yamashita, A.,Toy, A.
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p. 755 - 762
(2007/10/02)
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- THE SALT-FREE SYNTHESIS OF ARYL ETHERS USING METHYL TRICHLOROACETATE
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Metyl trichloroacetate is an effective reagent for salt-free synthesis of aryl ethers and anisoles from phenols.
- Renga, James M.,Wang, Pen-Chung
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- SELECTIVE DEALKYLATIONS OF ARYL ALKYL ETHERS AND THIOETHERS BY SODIUM IN HMPA
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The reaction of sodium with bis- and tris(alkoxy)benzenes in HMPA gives selectively the products of monodealkylation.The reaction proceeds through a dianion which fragments into an alkyl and an aryloxy anion.The positional selectivity of this fragmentation is governed by the structure of both the alkyl and aryloxy groups.With bis- and tris(alkoxy)benzenes which for symmetry reasons can afford aryloxy anions having the same basicity, the dealkylation involves exlusively the less substituted alkyl group.On the contrary, in the asymmetric terms, the positional selectivity of the dealkylation process is governed by the basicity of the aryloxy anion.On the basis of these concepts several efficient and synthetically useful reactions have been developed.In most cases the selectivity obtained in the present reactions in different from that observed with other previously developed methods which use sodium methoxide or sodium alkenethiolates in HMPA.It is shown that the appropriate choice of the reagent allows selective dealkylation of the desired alkoxy group of a poly(alkoxy)benzene.The reaction of sodium with bis(alkylthio)benzenes in HMPA gives the bis(mercapto)benzenes.If the reduction is carried out with a solution of sodium in HMPA, the reaction gives instead the products of monodealkylation.This however is not selective.It is suggested that in the case of thioethers the dealkylation products originate from the fragmentation of the radical anions.
- Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
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p. 3687 - 3692
(2007/10/02)
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- The Mechanism of the Reaction of (Aryloxy)trimethylstannane with Benzyl Bromide giving Aryl Benzyl Ether
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A kinetic study has been performed for the reaction of (aryloxy)trimethylstannane with benzyl bromide giving aryl benzyl ether and bromotrimethylstannane.Bimolecular nucleophilic attack of the aryloxy-oxygen on the benzyl-carbon has been suggested for the reaction based on the substituent effect.
- Kozuka, Seizi,Kikuchi, Akihiko,Yamaguchi, Shigeru
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p. 307 - 308
(2007/10/02)
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