- Pd-Catalyzed Etherification of Nitroarenes
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The Pd-catalyzed etherification of nitroarenes with arenols has been achieved using a new rationally designed ligand. Mechanistic insights were used to design the ligand so that both the oxidative addition and reductive elimination steps of a plausible catalytic cycle were facilitated. The catalytic system established here provides direct access to a range of unsymmetrical diaryl ethers from nitroarenes.
- Matsushita, Naoki,Kashihara, Myuto,Formica, Michele,Nakao, Yoshiaki
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supporting information
p. 2209 - 2214
(2021/07/20)
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- 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; 0077; 0081; 0109
(2021/11/19)
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- Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate
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Methods to activate the relatively stable ether C-O bonds and convert them to other functional groups are desirable. One-electron reduction of ethers is a potentially promising route to cleave the C-O bond. However, owing to the highly negative redox potential of alkyl aryl ethers (Ered -2.6 V vs SCE), this mode of ether C-O bond activation is challenging. Herein, we report the visible-light-induced photocatalytic cleavage of the alkyl aryl ether C-O bond using a carbazole-based organic photocatalyst (PC). Both benzylic and non-benzylic aryl ethers underwent C-O bond cleavage to form the corresponding phenol products. Addition of Cs2CO3 was beneficial, especially in reactions using a N-H carbazole PC. The reaction was proposed to occur via single-electron transfer (SET) from the excited-state carbazole to the substrate ether. Interaction of the N-H carbazole PC with Cs2CO3 via hydrogen bonding exists, which enables a deprotonation-assisted electron-transfer mechanism to operate. In addition, the Lewis acidic Cs cation interacts with the substrate alkyl aryl ether to activate it as an electron acceptor. The high reducing ability of the carbazole combined with the beneficial effects of Cs2CO3 made this otherwise formidable SET event possible.
- Yabuta, Tatsushi,Hayashi, Masahiko,Matsubara, Ryosuke
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p. 2545 - 2555
(2021/02/01)
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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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- 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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- 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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- 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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- 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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- Pd-catalyzed direct arylation approach to the 6H-dibenzo[c,h]chromenes: Total synthesis of arnottin I
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An efficient synthesis of 6H-dibenzo[c,h]chromenes has been achieved from 2-bromobenzyl-α-naphthyl ethers via a Pd-catalyzed Intramolecular direct-arylation using easily available Pd(PPh3)4 or Pd(OAc)2/PPh3 at elevated temperature. The reaction affords biaryl-coupling products in good to excellent yields in 6-9 h (up to 94% yields). A tentative mechanism has been proposed to understand the reaction pathway. Applying the methodology, a straightforward and concise total synthesis of arnottin I has been demonstrated by converting the biaryl-coupling products to the 6H-benzo[d]naphtho[1,2-b]pyran-6-one using pyridinium chlorochromate (PCC) mediated oxidation.
- De, Subhadip,Chaudhuri, Saikat,Mishra, Sourabh,Mamtani, Himanshu,Bisai, Alakesh
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p. 1871 - 1884
(2014/01/17)
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- Microwave-Assisted solid-liquid phase alkylation of naphthols
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The microwave promoted alkylation of 1- and 2-naphthols with benzyl, butyl, ethyl and isopropyl halides in the presence of an alkali carbonate may result in O- and C-Alkylated products. The alkylations were O-selective in the presence of K2CO3 in acetonitrile as the solvent and in the absence of phase transfer catalyst. The alkylations utilizing butyl and ethyl halides were also O-selective in solventless accomplishment and in the presence of triethylbenzylammonium chloride.
- Balint, Erika,Kovacs, Orsolya,Drahos, Laszlo,Keglevich, Gyoergy
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p. 330 - 336
(2013/07/26)
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- Highly efficient synthesis of phenols by copper-catalyzed hydroxylation of aryl iodides, bromides, and chlorides
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8-Hydroxyquinolin-N-oxide was found to be a very efficient ligand for the copper-catalyzed hydroxylation of aryl iodides, aryl bromides, or aryl chlorides under mild reaction conditions. This methodology provides a direct transformation of aryl halides to phenols and to alkyl aryl ethers. The inexpensive catalytic system showed great functional group tolerance and excellent selectivity.
- Yang, Kai,Li, Zheng,Wang, Zhaoyang,Yao, Zhiyi,Jiang, Sheng
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p. 4340 - 4343
(2011/10/08)
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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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- 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)
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- 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
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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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- Alkylation of phenols by oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone and alkoxydiphenylphosphine
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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
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- Alkylation of carbonyl compounds in water: Formation of C-C and C-O bonds in the presence of surfactants
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The formation of C-C and C-O bonds by the reaction of enolate intermediates with electrophilic substrates commonly requires strong bases, aprotic solvents and very low temperatures. A way of performing the same reactions with sodium hydroxide at moderate temperatures in aqueous surfactant solutions is presented. Different halides, ketones and surfactants (cationic, zwitterionic and anionic) have been used. The results obtained show that the amount of ketone alkylation is much higher and that the reactions are faster in the presence than in the absence of surfactant aggregates. The hydrolysis of the halide is minimised in the presence of cationic or zwitterionic surfactants.
- Cerichelli, Giorgio,Cerritelli, Simona,Chiarini, Marco,De Maria, Paolo,Fontana, Antonella
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p. 5204 - 5210
(2007/10/03)
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- Mediation of photochemical reactions of 1-naphthyl phenylacylates by polyolefin films. A 'radical clock' to measure rates of radical-pair cage recombinations in 'viscous space'
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The fates of phenylacyl/1-naphthoxy singlet radical pairs generated upon irradiation of 1-naphthyl phenylacetate (1a) and 1-naphthyl 2-phenylpropanoate (1b) in three unstretched and stretched polyethylene films and isotactic and syndiotactic polypropylene films have been investigated. From dynamic fluorescence measurements the primary locus of reactions by 1 is within amorphous regions of the films. The reaction cages afforded by these media inhibit escape of the radical pairs and mediate their reorientational motions leading to photo-Fries and related products. In essence, the cages act as stiff-walled templates. In addition, a method is described to measure the rate constants for the singlet radical pairs. Thus, the rate constants (leading to the keto precursors) of the 2-phenylacyl-1-naphthols from the radical pairs of 1 (> 108 s-1) are >6 times the rate constants for the 4-isomers. Film stretching increases this selectivity but there is no obvious correlation between the rate of the in-cage radical pair recombinations and macroscopic polymer, properties such as degree of crystallinity and frequency of branched chains. By contrast, formation of (the keto precursors of) 2-benzylic-1-naphthols (from in-cage recombinations after phenylacyl decarbonylation) is slower than for the 4-benzyl-1-naphthols. (C) 2000 Elsevier Science Ltd.
- Gu, Weiqiang,Weiss, Richard G.
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p. 6913 - 6925
(2007/10/03)
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- Systematic ranking of nucleophiles as electron donors
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A systematic ranking of different nucleophiles (including enolates, phenolates, thiophenolates, hydroxide, cyanide) with respect to their ability to stabilise the transition state of substitution reactions has been carried out in acetonitrile and dimethyl sulfoxide. The method is based on a comparison of the rate constant, kSUB, for the substitution reaction between a given nucleophile and benzyl chloride with the rate constant, kET, for the corresponding electron transfer from an aromatic radical anion to benzyl chloride. The ratio kSUB/kET expresses the rate enhancement due to electronic interaction in the transition state, ΔGSta, of the substitution reaction. In this study, kSUB/kET ratios between 5 and 1031 were determined corresponding to ΔGSta-values of 4-175 kJ mol-1. These values cover substitution reactions going from outer-sphere electron transfer to SN2 with partial bond formation in the transition state. The kSUB/kET values are found to be largest for nucleophiles such as OH- and CN- with very poor electron-donating abilities (high oxidation potentials). When different types of nucleophile with similar oxidation potentials are compared, a decrease in kSUB/kET is observed going from sulfur-to carbon- and further to oxygen-centred nucleophiles. The ranking of nucleophiles in reactions involving electrophiles other than benzyl chloride is discussed with emphasis on steric hindrance and electronic effects.
- Daasbjerg, Kim,Knudsen, Stig R.,Sonnichsen, Katrine N.,Andrade, Adalgisa R.,Pedersen, Steen U.
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p. 938 - 948
(2007/10/03)
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- Solid composite copper-copper chloride assisted alkylation of naphthols promoted by microwave irradiation
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Naphthyl ethers and naphthyl esters were synthesized in good yield by using mixture of copper metal powder and copper (II) chloride in conventional microwave oven in short time.
- Zadmard,Aghapoor,Bolourtchian,Saidi
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p. 4495 - 4499
(2007/10/03)
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- The synthesis and biological activity of two analogs of the anti-HIV alkaloid michellamine B
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Two simplified analogs of the dimeric naphthalenyltetrahydroisoquinoline alkaloid michellamine B [4',4''-didesmethoxy-2',2''-didesmethylmichellamine B and 6,8-dihydroxy-5-(1',1''-dihydroxy-2',2''-binaphthalen-4'-yl)-1R,3R-dim ethyl-1,2,3,4-tetrahydroisoqu
- Upender,Pollart,Liu,Hobbs,Olsen,Chao,Bowden,Crase,Thomas,Pandey,Lawson,Dawson
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p. 1371 - 1385
(2007/10/03)
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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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- Ameliorations et simplification de la synthese des ethers phenoliques par alkylation d'ions phenates: catalyse par transfert de phase solide-liquide sans solvant
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Several aryl ethers can be obtained in excellent yields under mild and economical conditions in the absence of organic solvents by reacting stoechiometric amounts of corresponding phenol, finely ground KOH and alkyl bromides in the presence of 2percent Aliquat 336.This method is very favourable compared with recent works dealing with anionic activation.
- Loupy, Andre,Sansoulet, Jean,Zand, Farchid Vaziri-
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p. 1027 - 1035
(2007/10/02)
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- Electron Apportionment in Cleavage of Radical Anions. 2. Naphthylmethyl Phenyl Ethers vs. Naphthyl Benzyl Ethers
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Naphthylmethyl phenyl ethers and naphthyl benzyl ethers were found to undergo scission of the H2C-O bond when treated with radical anions of anthracene or fluoranthene.Under comparable conditions, ethers of the naphthylmethyl phenyl series (α and β) reacted more than 10E4 times faster than ethers of the naphthyl benzyl series (α and β).This preference for regioconservation of spin density in the scission process is interpreted in terms of ?-bond polarization at the transition state.
- Maslak, Przemyslaw,Guthrie, Robert D.
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p. 2637 - 2640
(2007/10/02)
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- Mechanism of Reactions Promoted by Polymer-Supported Phase-Transfer Catalysts
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Kinetic measurements indicate that the ratio of C- vs.O-alkylation of β-naphthoxide is not a reliable polarity test for polymer-supported phase-transfer catalysis because of the competitive noncatalyzed reactions.A reliable test is the C/O-alkylation of phenoxide.Reactions carried out in toluene-water in the presence of stoichiometric amounts of polystyrene-supported quaternary phosphonium salts 2 and 3 afford only O-alkylation products.Stoichiometric reactions give significant amounts of C-alkylation with 2 or 3 in aqueous ethanol or with immobilized polar catalysts 4 and 5 in toluene-water.Hydration measurements agree with the essentially hydrophobic character of polystyrene-supported phosphonium catalysts 2 and 3.These results confirm our previous conclusion that phase-transfer catalysis follows identical mechanisms both in the presence of soluble and polymer-supported catalysts.In the latter case the reaction should occur within an organic solvation shell firmly surrounding the catalytic site, rather than in an aqueous solvation sphere or at the interface.
- Montanari, Fernando,Quici, Silvio,Tundo, Pietro
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p. 199 - 202
(2007/10/02)
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- Kinetics of Benzylation of Hydroxypyridines & Hydroxyquinolines in Dimethyl Sulphoxide - Water & Isopropanol - Water Mixtures
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The kinetics of benzylation of hydroxypyridines and hydroxyquinolines have been investigated in DMSO-water and isopropanol-water mixtures.A formal comparison of rate of benzylation of phenols and naphthols has also been made.DMSO, being a dipolar aprotic solvent facilitates O-alkylation of phenols and naphthols and a considerable rate increase has been observed in DMSO-water, giving the O-alkylated products in more than 90percent yield in both the cases.However, in the case of benzylation of hydroxypyridine in DMSO-water, O-alkylated product formed is only 65percent and the magnitude of rate increase, compared to phenols and naphthols, is much less, under similar conditions.But the rate of benzylation of 8-hydroxyquinoline in DMSO-water is retarded considerably and the rate is even slower than the rate of N-benzylation of quinoline, indicating only O-benzylation of 8-hydroxyquinoline in DMSO-water is unique and is mainly due to greater ground state solvation of substrate by DMSO, a factor which has been considered insignificant in all the other cases.
- Rajasekar, N.,Srinivasan, V. S.,Venkatasubramanian, N.
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p. 800 - 802
(2007/10/02)
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