- Oxalohydrazide Ligands for Copper-Catalyzed C?O Coupling Reactions with High Turnover Numbers
-
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.
-
supporting information
p. 8203 - 8211
(2021/03/08)
-
- Transition-Metal-Free and Base-Promoted Carbon-Heteroatom Bond Formation via C-N Cleavage of Benzyl Ammonium Salts
-
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
-
p. 4159 - 4170
(2021/03/09)
-
- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
-
A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
-
supporting information
p. 2095 - 2103
(2021/03/26)
-
- MALIC ENZYME INHIBITORS
-
The present invention relates to novel compounds useful as malic enzyme (ME) inhibitors, processes for their preparation and use of these compounds for the therapeutic treatment of disorders mediated by ME such as cancers (e.g. pancreatic ductal adenocarcinoma (PDAC)) in humans.
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-
Page/Page column 94
(2021/04/23)
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- α-Lithiobenzyloxy as a Directed Metalation Group in ortho-Lithiation Reactions
-
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
-
supporting information
p. 6365 - 6369
(2020/08/24)
-
- To the methoxy ethyl phenol synthesis method (by machine translation)
-
The invention discloses a method for synthesizing methoxy ethyl phenol, to the chlorophenol as the starting material, through the phenolic hydroxyl protection, format reaction, methylation and hydrogenation debenzylation reaction to obtain the target product to the methoxy ethyl phenol process, the methylation reaction is just a simple filtering operation that can be used for the next step reaction, without any other operation. This invention adopts the [...] as the starting material to synthesize to methoxy ethyl phenol, reduce the difficulty of after treatment, reduce the reaction time, the product has high purity, high yield, good stability of the product. (by machine translation)
- -
-
Paragraph 0025-0030
(2018/11/04)
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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
-
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
-
supporting information
p. 15058 - 15068
(2016/10/11)
-
- Deuterodechlorination of Aryl/Heteroaryl Chlorides Catalyzed by a Palladium/Unsymmetrical NHC System
-
The catalytic deuterodechlorination of aryl/heteroaryl chlorides was developed with a palladium/unsymmetrical NHC system, and the precisely controlled introduction of deuterium into a variety of aryl/heteroaryl compounds was achieved with a high level of efficiency, selectivity, and deuteration degree. This method was also successfully applied to the transformation of bioactive agents even in a gram-scale synthesis. The crystal structure analysis of Pd-NHC complexes led to the observation of Pd-arene interaction.
- Kuriyama, Masami,Hamaguchi, Norihisa,Yano, Gemba,Tsukuda, Kotaro,Sato, Kanako,Onomura, Osamu
-
p. 8934 - 8946
(2016/10/14)
-
- α-Lithiated Aryl Benzyl Ethers: Inhibition of [1,2]-Wittig Rearrangement and Application to the Synthesis of Benzo[b]furan Derivatives
-
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
-
supporting information
p. 4416 - 4419
(2015/09/28)
-
- Copper-catalyzed Ullmann-type synthesis of diaryl ethers assisted by salicylaldimine ligands
-
A series of salicylaldimine ligands were designed to promote the copper-catalyzed Ullmann cross-coupling reaction. After a screening process, 2-((2-isopropylphenylimino)methyl)phenol was found to serve as a good supporting ligand for this reaction. Employing this Schiff-base ligand as a new supporting ligand, the copper-catalyzed coupling reactions of aryl bromides and aryl iodides with various phenols successfully proceeded in good yields under mild conditions. Various diaryl ethers were obtained with excellent yields in dioxane in the presence of K3PO4 and a catalytic amount of copper(I) salt.
- Qian, Cun-Wei,Lv, Wen-Lin,Zong, Qian-Shou,Wang, Mao-Yuan,Fang, Dong
-
p. 337 - 340
(2014/02/14)
-
- Tetrabutyl ammonium bromide-mediated benzylation of phenols in water under mild condition
-
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
-
p. 2669 - 2673
(2014/04/03)
-
- Choline chloride based deep eutectic solvent as an efficient solvent for the benzylation of phenols
-
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)
-
- Metal-free synthesis of aryl ethers in water
-
The first arylation of allylic and benzylic alcohols with diaryliodonium salts is reported. The reaction yields alkyl aryl ethers under mild and metal-free conditions. Phenols are arylated to diaryl ethers in good to excellent yields. The reaction employs diaryliodonium salts and sodium hydroxide in water at low temperature, and excess amounts of the coupling partners are avoided.
- Lindstedt, Erik,Ghosh, Raju,Olofsson, Berit
-
supporting information
p. 6070 - 6073
(2014/01/06)
-
- NiCl2·6H2O/NaBH4 in methanol: A mild and efficient strategy for chemoselective deallylation/debenzylation of aryl ethers
-
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.
-
supporting information
p. 4540 - 4543
(2013/08/23)
-
- Methenamine as an efficient ligand for copper-catalyzed coupling of phenols with aryl halides
-
Employing methenamine as a new supporting ligand, the copper-catalyzed coupling reactions of aryl bromides or aryl iodides with various phenols successfully proceeded in good yields under mild conditions. A series of diaryl ethers were obtained with excellent yields in the presence of K 3PO4 and copper(I) salt. Copyright
- Qian, Cunwei,Zong, Qianshou,Fang, Dong
-
experimental part
p. 199 - 203
(2012/03/11)
-
- Metal-free chlorodeboronation of organotrifluoroborates
-
A mild and metal-free method for the chlorodeboronation of organotrifluoroborates using trichloroisocyanuric acid (TCICA) was developed. Aryl-, heteroaryl-, alkenyl-, alkynyl-, and alkyltrifluoroborates were converted into the corresponding chlorinated products in good yields. This method proved to be tolerant of a broad range of functional groups.
- Molander, Gary A.,Cavalcanti, Livia N.
-
experimental part
p. 7195 - 7203
(2011/10/13)
-
- Microwave-assisted alkylation of phenols by quaternary onium salts
-
The alkylation of cresol and its analogues was accomplished by quaternary onium salts under solventless and microwave(MW) conditions using Cs 2CO3 as the base. The beneficial energy absorbing ability of the onium saltscould be clearly observed under MW conditions as compared to the thermal experiments and was relevant in the range of 110-125 °C.
- Blint, Erika,Greiner, Istvan,Keglevich, Gyrgy
-
experimental part
p. 22 - 27
(2012/04/10)
-
- C(sp3)-O bond-forming reductive elimination of ethers from bisphosphine-ligated benzylpalladium(II) aryloxide complexes
-
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.
-
supporting information; experimental part
p. 7119 - 7123
(2011/09/16)
-
- Liquid ammonia as a dipolar aprotic solvent for aliphatic nucleophilic substitution reactions
-
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.
-
supporting information; scheme or table
p. 1425 - 1435
(2011/04/23)
-
- Heterogeneous phase alkylation of phenols making use of phase transfer catalysis and microwave irradiation
-
The benzylation of cresol was studied under liquid-liquid and solid-liquid phase transfer catalytic conditions. Microwave irradiation was useful only in the solid-liquid phase benzylations. Using acetonitrile as the solvent, the benzylations were fully O-selective, but complete conversions were obtained only in the presence of Cs2CO3. There was no need to use an onium salt. In the absence of solvent, an O-selectivity of ca. 90% could be obtained in the presence of an alkali carbonate and an onium salt. The optimum set of conditions was extended to the reaction of other phenol derivatives and alkylating agents.
- Keglevich, Gyoergy,Balint, Erika,Karsai, Eva,Varga, Judit,Gruen, Alajos,Balint, Maria,Greiner, Istvan
-
experimental part
p. 535 - 539
(2010/04/23)
-
- Counterattack mode differential acetylative deprotection of phenylmethyl ethers: Applications to solid phase organic reactions
-
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.
-
supporting information; experimental part
p. 1367 - 1370
(2009/07/04)
-
- Discovery of GSK345931A: An EP1 receptor antagonist with efficacy in preclinical models of inflammatory pain
-
Herein we describe the medicinal chemistry programme to identify a potential back-up compound to the EP1 receptor antagonist GW848687X. This work started with the lipophilic 1,2-biaryl benzene derivative 4 which displayed molecular weight of 41
- Hall, Adrian,Brown, Susan H.,Budd, Christopher,Clayton, Nicholas M.,Giblin, Gerard M.P.,Goldsmith, Paul,Hayhow, Thomas G.,Hurst, David N.,Naylor, Alan,Anthony Rawlings,Scoccitti, Tiziana,Wilson, Alexander W.,Winchester, Wendy J.
-
scheme or table
p. 497 - 501
(2011/03/18)
-
- Benzyl protection of phenols under neutral conditions: Palladium-catalyzed benzylations of phenols
-
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
-
supporting information; experimental part
p. 1979 - 1982
(2009/04/10)
-
- Chemoselectivity in the microwave-assisted solvent-free solid-liquid phase benzylation of phenols: O- versus C-alkylation
-
The outcome of the solvent-free benzylation of phenol and 4-substituted phenols (such as 4-cresol and 4-chlorophenol) under MW irradiation was found to depend on the absence or presence of the base (K2CO3) and catalyst (triethylbenzy
- Keglevich, Gy?rgy,Bálint, Erika,Karsai, éva,Grün, Alajos,Bálint, Mária,Greiner, István
-
p. 5039 - 5042
(2008/12/22)
-
- PYRIDYL COMPOUNDS
-
Compounds of formula (I) or a pharmaceutically acceptable derivative thereof: wherein R1, R2, and R3 are as defined in the specification, a process for the preparation of such compounds, pharmaceutical compositions compris
- -
-
Page/Page column 27
(2008/06/13)
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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
-
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
-
p. 7359 - 7367
(2007/10/03)
-
- 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
-
p. 1645 - 1667
(2007/10/03)
-
- Uncatalyzed Friedel-Crafts alkylation of aromatic compounds through reactive benzyl cations generated from N-sulfamoylcarbamates
-
(Matrix presented) A new method for the generation of highly reactive benzyl cations by thermal decomposition of aryl-benzyl-sulfamoylcarbamates, obtained in a one-pot reaction from chlorosulfonyl isocyanate, is described. The generated cations alkylate aromatic compounds efficiently in the absence of catalysts.
- Sefkow, Michael,Buchs, Jens
-
p. 193 - 196
(2007/10/03)
-
- Ionic liquid as an efficient promoting medium for two-phase nucleophilic displacement reactions
-
The use of the room temperature ionic liquid (RTIL) 1-n-butyl-3-methylimidazolium hexafluorophosphate as an efficient catalyst and solvent for several representative nucleophilic substitution reactions under aqueous-RTIL phase transfer conditions was explored. Recycling and reuse of the reaction medium was demonstrated for the azide formation.
- Louren?o, Nuno M.T.,Afonso, Carlos A.M.
-
p. 789 - 794
(2007/10/03)
-
- Bu3SnH mediated oxidative radical cyclisations: Synthesis of 6H-benzo[c]chromen-6-ones
-
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
-
p. 2991 - 2999
(2007/10/03)
-
- Polymer-bound triphenylphosphine as traceless reagent for Mitsunobu reactions in combinatorial chemistry: Synthesis of aryl ethers from phenols nad alcohols
-
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.
-
p. 8751 - 8754
(2007/10/03)
-
- New synthetic method of aromatic ethers under microwave irradiation in dry media
-
Under microwave irradiation a number of phenols react remarkably fast with a number of primary alkyl halides to give aromatic ethers.
- Bogdal, Dariusz,Pielichowski, Jan,Boron, Adam
-
p. 3029 - 3039
(2007/10/03)
-
- Isotope effects in nucleophilic substitution reactions X. The effect of changing the nucleophilic atom on ion-pairing in an S(N)2 reaction
-
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)
-
- Kaolin-assisted Aromatic Chlorination and Bromination
-
Moist kaolin catalyses the regioselective and high-yielding chlorination and bromination of C6H5OR (R = C1-C8 alkyl. Bu1, allyl, cyclohexyl, benzyl) to 4-XC6H4OR (X = Cl and Br, respectively) with NaCl02 and Mn(acac)3 in CH2Cl2 in the absence and presence of NaBr, respectively, under mild and neutral conditions.
- Hirano, Masao,Monobe, Hiroyuki,Yakabe, Shigetaka,Morimoto, Takashi
-
p. 662 - 663
(2007/10/03)
-
- Selective aromatic chlorination of activated arenes with sodium chlorite, (salen)manganese(III) complex, and alumina in dichloromethane
-
The reaction of alkyl phenyl ethers with sodium chlorite in dichloromethane in the presence of a (salen)manganese(III) complex and alumina preloaded with a small amount of water afforded monochlorination products with unusually high para selectivities under mild conditions. The NaClO2-based biphasic system can also be successfully used for the regioselective monochlorination of substituted anisoles and polymethoxybenzenes.
- Hirano,Yakabe,Monobe,Morimoto
-
p. 1905 - 1912
(2007/10/03)
-
- Oxidation potential as a measure of the reactivity of anionic nucleophiles. Behaviour of different classes of nucleophiles
-
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)
-
- Novel Synthesis of N,N-Diarylarylmethanamines from N-(Arylmethylene)arenamines and (Arylmethoxy)arenes
-
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.
-
p. 5875 - 5882
(2007/10/02)
-
- The Mechanism of the Reaction of (Aryloxy)trimethylstannane with Benzyl Bromide giving Aryl Benzyl Ether
-
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
-
p. 307 - 308
(2007/10/02)
-