- Reaction Cycling for Kinetic Analysis in Flow
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A reactor capable of efficiently collecting kinetic data in flow is presented. Conversion over time data is obtained by cycling a discrete reaction slug back and forth between two residence coils, with analysis performed each time the solution is passed between the two. In contrast to a traditional steady-state continuous flow system, which requires upward of 5× the total reaction time to obtain reaction progress data, this design achieves much higher efficiency by collecting all data during a single reaction. In combination with minimal material consumption (reactions performed in 300 μL slugs), this represents an improvement in efficiency for typical kinetic experimentation in batch as well. Application to kinetic analysis of a wide variety of transformations (acylation, SNAr, silylation, solvolysis, Pd catalyzed C-S cross-coupling and cycloadditions) is demonstrated, highlighting both the versatility of the reactor and the benefits of performing kinetic analysis as a routine part of reaction optimization/development. Extension to the monitoring of multiple reactions simultaneously is also realized by operating the reactor with multiple reaction slugs at the same time.
- Newman, Stephen G.,Sullivan, Ryan J.
-
supporting information
p. 5464 - 5474
(2020/05/19)
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- Auto-Tandem Catalysis with Frustrated Lewis Pairs for Reductive Etherification of Aldehydes and Ketones
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Herein we report that a single frustrated Lewis pair (FLP) catalyst can promote the reductive etherification of aldehydes and ketones. The reaction does not require an exogenous acid catalyst, but the combined action of FLP on H2, R-OH or H2O generates the required Br?nsted acid in a reversible, “turn on” manner. The method is not only a complementary metal-free reductive etherification, but also a niche procedure for ethers that would be either synthetically inconvenient or even intractable to access by alternative synthetic protocols.
- Bakos, Mária,Gy?m?re, ádám,Domján, Attila,Soós, Tibor
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supporting information
p. 5217 - 5221
(2017/04/27)
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- Decomposition of a Β-O-4 lignin model compound over solid Cs-substituted polyoxometalates in anhydrous ethanol: acidity or redox property dependence?
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Production of aromatics from lignin has attracted much attention. Because of the coexistence of C–O and C–C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone (2-PAP), was investigated over several cesium-exchanged polyoxometalate (Cs-POM) catalysts. Decomposition of 2-PAP can follow two different mechanisms: an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox properties of the catalysts. The catalysts of POMs perform the following functions: promoting active hydrogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen liberation and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP (>99%) with excellent selectivities to the desired products (98.6% for phenol and 91.1% for acetophenone) can be achieved.
- Wu, Xuezhong,Jiao, Wenqian,Li, Bing-Zheng,Li, Yanming,Zhang, Yahong,Wang, Quanrui,Tang, Yi
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p. 1216 - 1228
(2017/07/10)
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- Direct and efficient synthesis of unsymmetrical ethers from alcohols catalyzed by Fe(HSO4)3 under solvent-free conditions
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Highly efficient Fe(HSO4)3 catalyzed etherification of primary, secondary and tertiary benzylic alcohols with primary and secondary aliphatic alcohols is reported. The reaction affords unsymmetrical benzyl ethers in good to excellent yields under solvent-free conditions.
- Moghadam, Bashir Nazari,Akhlaghinia, Batool,Rezazadeh, Soodabeh
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p. 1487 - 1501
(2016/04/26)
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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- Direct C-H bond activation of ethers and successive C-C bond formation with benzene by a bifunctional palladium-titania photocatalyst
-
Palladium-loaded titanium oxide was found to work as a bifunctional photocatalyst for functionalization of benzene with ether upon photoirradiation, without using any special reagents. The metal-loaded TiO2 photocatalyst activated a C-H bond of ethers and the heterogeneous Pd metal nanoparticle catalyst promoted the successive C-C bond formation between benzene and the radical species. In this reaction, benzene reacted very selectively with the α-carbon of various ethers at least in the initial stage of the reaction. Kinetic and ESR studies revealed a detailed mechanism for the reaction.
- Tyagi, Akanksha,Matsumoto, Tomoya,Kato, Tatsuhisa,Yoshida, Hisao
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p. 4577 - 4583
(2016/07/06)
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- Organohalide-catalyzed dehydrative O-alkylation between alcohols: A facile etherification method for aliphatic ether synthesis
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Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.
- Xu, Qing,Xie, Huamei,Chen, Pingliang,Yu, Lei,Chen, Jianhui,Hu, Xingen
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supporting information
p. 2774 - 2779
(2015/05/27)
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- Selective catalytic synthesis of unsymmetrical ethers from the dehydrative etherification of two different alcohols
-
The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4- catalyzes selective etherification of two different alcohols to form unsymmetrically substituted ethers. The catalytic method exhibits a broad substrate scope while tolerating a range of heteroatom functional groups in forming unsymmetrical ethers, and it is successfully used to directly synthesize a number of highly functionalized chiral nonracemic ethers.
- Kim, Junghwa,Lee, Dong-Hwan,Kalutharage, Nishantha,Yi, Chae S.
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p. 3881 - 3885
(2015/01/16)
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- Multimetallic Ir-Sn3-catalyzed substitution reaction of π-activated alcohols with carbon and heteroatom nucleophiles
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An atom economic and catalytic substitution reaction of π-activated alcohols by a multimetallic IreSn3 complex has been demonstrated. The multimetallic IreSn3 complex can be easily synthesized from the reaction between [Cp*IrCl2]2 and SnCl2. In presence of as little as 1 mol % of the catalyst three different types of π-activated alcohols, namely benzyl, allyl, and propargyl alcohols, have been successfully transformed into alkylated products using carbon (arenes, heteroarenes, allyltrimethylsilane, and 1,3-dicarbonyls), nitrogen (sulfonamides), oxygen (alcohols), and sulfur (thiols) nucleophiles in very high yields. An electrophilic mechanism is proposed from the Hammett correlation study.
- Maity, Arnab Kumar,Chatterjee, Paresh Nath,Roy, Sujit
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p. 942 - 956
(2013/07/25)
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- Novel gallium and indium salts of the 12-tungstophosphoric acid: Synthesis, characterization and catalytic properties
-
The objective of this study was the preparation, characterization and testing of the catalytic properties of the GaPW12O40 and InPW12O40 salts of 12-tungstophosphoric heteropolyacid (HPW). The samples were characterized by XRD, IR, SEM, and 31P and 1H MAS NMR spectroscopy. The acid properties of the solids were directly accounted for by applying 1H MAS NMR. The salts were screened in the etherification of 1-phenylethanol with C1-C 4 alkanols in dichloromethane as a solvent to yield the corresponding C6H5CH(OR)CH3 unsymmetrical ethers. In comparison with pure HPW, the new salts revealed generally a higher selectivity of ethers formation at 65 °C.
- Filek, Urszula,Mucha, Dariusz,Hunger, Michael,Sulikowski, Bogdan
-
-
- Catalytic hydroalkoxylation of alkenes by iron(III) catalyst
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Catalytic hydroalkoxylation of alkenes by iron(III) chloride in the presence of toluenesulfonic acid (TsOH) was developed in moderate to good yields up to 91%. Intramolecular cyclization of 5-hydroxyl pentene afforded 2-methyltetrahedronfuran in 63% yield.
- Ke, Fang,Li, Zhengkai,Xiang, Haifeng,Zhou, Xiangge
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supporting information; experimental part
p. 318 - 320
(2011/02/26)
-
- Triflic acid catalyzed reductive coupling reactions of carbonyl compounds with O-, S-, and N-nucleophiles
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Highly efficient metal-free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid (1-5 mol %) as the catalyst are presented. The reactions can be performed at ambient temperature without exclusion of moisture or air. A range of symmetrical and unsymmetrical ethers were obtained by this method in high yields and short reaction times. For the first time, the influence of additional functionalization has been studied. Furthermore, the formation of thioethers from ketones (by addition of unmodified thiols) and of sulfonamides from either aldehydes or ketones has been achieved under catalytic conditions.
- Gellert, Beate A.,Kahlcke, Nils,Feurer, Markus,Roth, Stefanie
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supporting information; experimental part
p. 12203 - 12209
(2011/11/07)
-
- Silica-supported KHSO4: An efficient system for activation of aromatic terminal olefins
-
Potassium hydrogen sulfate adsorbed on chromatography-grade silica gel activates electron-rich aromatic terminal olefins towards nucleophilic attack at the benzylic position by alcohols. Temperature plays a crucial role and facilitates suppressing nucleophilic reaction in favor of dimerization of the terminal olefin. Georg Thieme Verlag Stuttgart - New York.
- Das, Ram Nath,Sarma, Kuladip,Pathak, Madan Gopal,Goswami, Amrit
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supporting information; experimental part
p. 2908 - 2912
(2011/02/25)
-
- Efficient addition of alcohols, amines and phenol to unactivated alkenes by AuIII or PdII stabilized by CuCl2
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The nucleophilic addition of alcohols, amines and phenol to unactivated alkenes catalyzed by cationic gold and palladium becomes limited due to the fast reduction into metallic gold under reaction conditions. The presence of CuCl2 retards the reduction of AuIII and PdII, strongly increasing the turnover number of gold and palladium catalysts. It is shown that new AuIII-CuCl2 and PdII-CuCl 2 catalysts are active and selective for the nucleophilic addition of alcohols, amines and phenol to unactivated alkenes. This journal is The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 397 - 403
(2008/09/17)
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- An efficient one-pot synthesis of unsymmetrical ethers: A directly reductive deoxygenation of esters using an InBr3/Et3SiH catalytic system
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(Chemical Equation Presented) This study describes a novel one-pot procedure for a directly reductive conversion of the carbonyl function of esters to the corresponding ethers by Et3SiH in the presence of a catalytic amount of InBr3.
- Sakai, Norio,Moriya, Toshimitsu,Konakahara, Takeo
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p. 5920 - 5922
(2008/02/09)
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- Secondary benzylation with benzyl alcohols catalyzed by a high-valent heterobimetallic Ir-Sn complex
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(Chemical Equation Presented) A highly efficient secondary benzylation procedure has been demonstrated using a high-valent heterobimetallic complex [Ir2(COD)2(SnCls)2(Cl)2(μ-Cl) 2] 1 as the catalyst in 1,2-dichloroethane to afford the corresponding benzylated products in moderate to excellent yields. The reaction was performed not only with carbon nucleophiles (arenes and heteroarenes) but also with oxygen (alcohol), nitrogen (amide and sulfonamide), and sulfur (thiol) nucleophiles. Mechanistic investigation showed the intermediacy of the ether in this reaction. An electrophilic mechanism is proposed from Hammett correlation.
- Podder, Susmita,Choudhury, Joyanta,Roy, Sujit
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p. 3129 - 3132
(2008/02/07)
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- Iodine catalyzed selective O-alkylation of alcohols with orthoesters
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In the present communication O-alkylation of a number of allylic and benzylic alcohols has been described.
- Kumar,Anjaneyulu,Joyasawal, Sipak,Pawan Chakravarthy,Naveen Kumar,Yadav
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p. 189 - 192
(2008/02/13)
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- Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes
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Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl2 are added, which significantly stabilize the cationic Au(III). The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 3080 - 3082
(2008/02/10)
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- Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study
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Allylic and benzylic alcohols are converted into corresponding unsymmetrical ethers when reacted with various orthoesters in the presence of montmorillonite KSF at ambient temperature. A detailed study has been undertaken to examine the mechanism and generality of these reactions with regard to various acidic catalysts, which reveal interesting competitive reactions mainly O-acetylation, together with trace amount of dimerized product. The type of the side product and their relative quantity depends upon the nature of the catalyst employed. Furthermore, the low yields of the Claisen rearrangement product obtained from allylic alcohols under heating is rationalized due to the formation of some of these products.
- Sampath Kumar,Joyasawal, Sipak,Reddy,Pawan Chakravarthy,Krishna,Yadav
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p. 1686 - 1692
(2007/10/03)
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- Palladium-catalyzed SN1 reactions of secondary benzylic alcohols: Etherification, amination, and thioetherification
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The reaction of various secondary benzylic alcohols in the presence of PdII catalysts provides ethers in good to high yields, Unsymmetric ethers could also be obtained with good selectivity by coupling two different alcohols. Direct amination is observed with electron-deficient anilines, and thioethers are prepared conveniently in high yields by the direct action of thiols on sec-phenylethyl alcohol. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Miller, Kimberly J.,Abu-Omar, Mahdi M.
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p. 1294 - 1299
(2007/10/03)
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- Substitution of α-azido ethers with Grignard reagents and its use in combinatorial chemistry
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α-Azidobenzyl ethers were reacted with alkyl or arylGrignard reagents in toluene to produce α-alkylbenzyl or diarylmethyl ethers in 82-94% yield. α-Azidobenzyl ethers were also reacted with multicomponent Grignard reagents to produce libraries of α-alkylbenzyl ethers.
- Baruah, Mukulesh,Bols, Mikael
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p. 509 - 512
(2007/10/03)
-
- Chemical equilibrium study in the reacting system of the (1-alkoxyethyl)benzene synthesis from alkanols and styrene
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The chemical equilibrium of the reactive system alkanol + styrene ? (1-alkoxyethyl)benzene (where alkyl is methyl, ethyl, propyl, and butyl) was studied in the liquid phase at 343-423 K using a cation exchanger as the heterogeneous catalyst. Enthalpies of reactions of (1-alkoxyethyl)benzene synthesis in the liquid phase were obtained from the temperature dependence of equilibrium constants measured in the reactive mixtures with an excess of alkanol and indicated a good agreement with those reaction enthalpies derived from values of the enthalpies of formation (liquid) of the reactions participants measured for (1-methoxyethyl)benzene and (1-butoxyethyl)benzene by combustion calorimetry. Isopropylbenzene was a relevant structural pattern of strain in the (1-alkoxyethyl)benzenes studied. Its strain enthalpy was a reflection of the intrinsic strain of the molecule due to steric repulsions of methyl tertiary carbon atom. No additional group additivity parameters or correction terms were required for the group contribution correlation for enthalpies of formation (gas) of (1-alkoxyethyl)benzenes.
- Verevkin, Sergey,Heintz, Andreas
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p. 984 - 990
(2007/10/03)
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- Tri-n-butylstannyl chloride-sodium cyanoborohydride mediated regioselective reductive demethoxylation of alkyl methyl ketals
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A regioselective reductive demethoxylation of alkyl methyl ketals employing sodium cyanoborohydride in the presence of a catalytic amount of tri-n-butyltin chloride as Lewis acid is described.
- Srikrishna,Viswajanani
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p. 621 - 625
(2007/10/03)
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- Reductive cleavage of acetals/ketals with ZrCl4/NaBH4
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Reductive cleavage of acetals/ketals with zirconium tetrachloride- sodium borohydride leading to the formation of ether alcohols is described.
- Purushothama Chary,Santosh Laxmi,Iyengar
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p. 1257 - 1261
(2007/10/03)
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- Organic reactions catalyzed by methylrhenium trioxide: Dehydration, amination, and disproportionation of alcohols
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Methylrhenium trioxide (MTO) is the first transition metal complex in trace quantity to catalyze the direct formation of ethers from alcohols. The reactions are independent of the solvents used: benzene, toluene, dichloromethane, chloroform, acetone, and in the alcohols themselves. Aromatic alcohols gave better yields than aliphatic. Reactions between two different alcohols could also be used to prepare unsymmetric ethers, the best yields being obtained when one of the alcohols is aromatic. MTO also catalyzes the dehydration of alcohols to form olefins at room temperature, aromatic alcohols proceeding in better yield. When primary (secondary) amines were used as the limiting reagent, direct amination of alcohols catalyzed by MTO gave good yields of the expected secondary (tertiary) amines at room temperature. Disproportionation of alcohols to alkanes and carbonyl compounds was also observed for aromatic alcohols in the presence of MTO. On the basis of the results of this investigation and a comparison with the interaction between MTO and water, a concerted process and a mechanism involving carbocation intermediates have been suggested.
- Zhu, Zuolin,Espenson, James H.
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p. 324 - 328
(2007/10/03)
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- BORON FLUORIDE PROMOTED CLEAVAGE OF ACETALS BY ORGANOCOPPER REAGENTS. APPLICATION TO ASYMMETRIC SYNTHESIS
-
In the presence of BF3*Et2O, organocopper and cuprate reagents promote the substitution of one alkoxy group of an acetal.Under the same conditions, alkoxy tetrahydropyrans react selectively, by ring cleavage.Chiral cyclic acetals, having a C2 axis of symmetry are diastereoselectively cleaved.The method serves to synthesize chiral secondary alcohols, after the removal of the chiral auxiliary.
- Normant, J. F.,Alexakis, A.,Ghribi, A.,Mangeney, P.
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p. 507 - 516
(2007/10/02)
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- Reactions of Phenylmagnesium Chloride and Phenyllithium with Thianthrene Cation Radical Perchlorate. Evidence for Electron Transfer: Formation and Decomposition of 5-Substituted Thianthreniumyl Perchlorates
-
Reaction of thianthrene cation radical perchlorate (Th+ClO4-), suspended in either ether or THF, with PhMgCl, and reaction of Th+ClO4-, suspended in ether, with PhLi in C6H12/ether, gave largely benzene and Th. 5-Phenylthianthreniumyl perchlorate (1a) was formed in the Grignard reactions but was not obtained in the PhLi reaction.Diphenyl sulfide (Ph2S) and dibenzothiophene (DBT) were obtained with PhMgCl and PhLi in ether, but not with PhMgCl in THF.Small amounts of ethyl 1-phenylethyl ether and 2-phenylethyltetrahydrofuran (PhTHF) were also formed.Reaction with PhMgCl in THF-d8 and with PhLi in (C2D5)2O gave a mixture of C6H6 and C6H5D.These results show that phenyl radical (Ph) was formed in the cation radical reactions and abstracted H(D) atom from the solvent.The results suggest also that Ph was trapped by Th+, leading to 1a.However as shown with control reactions, 1a reacted further with PhMgCl (slowly) and PhLi (rapidly) and was converted into Ph2S and DBT.Control reaction of PhLi with 1a gave Ph2S and DBT in high, approximately equal yields.Reaction with 5-(p-tolyl)thianthreniumyl perchlorate (1b) analogously gave phenyl p-tolyl sulfide and DBT.Reaction of PhMgCl with 1a was slow and incomplete and gave not only Ph2S and DBT but also some 2-phenyl-2'-(phenylthio)diphenyl sulfide (2a) and a mixture of 1- and 2-phenylthianthrene (together designated as 3a).An analogous reaction occured between PhMgCl and 1b.Reaction of 1a with BuMgCl gave BuSPh and DBT, some 2-(phenylthio)diphenyl sulfide (4), and some 2-(butylthio)-2'-phenyldiphenyl sulfide (5a).In contrast, reaction of PhMgCl with 5-butylthianthreniumyl perchlorate (1e) gave mainly benzene and Th, while reaction of BuMgCl with 1e gave mainly butane, octane, and Th analog with a small amount of 2-butyl-2'-(butylthio)diphenyl sulfide (5e).Reaction of PhLi with 1e and its analogues 5-methyl- and 5-ethylthianthreniumyl perchlorate (1c and 1d, respectively) gave benzene, Th, the corresponding alkyl phenyl sulfide and DBT, and small amounts of 2-(alkylthio)-2'-phenyldiphenyl sulfide (2c-e).Formation of benzene in these reactions is attributed to deprotonation of the alkyl group in 1c-e and concomitant formation of an ylide (6-8).Ylide 6, from reaction of PhLi with 1c, was trapped by reactions with subsequently added water and phenol (reconverting 6 to 1c) and with added benzophenone, leading to Th and 1,1-diphenyloxirane (9).Diphenylmercury did not react with 1a in acetonitrile solution.The apparent complexity of reactions of Th+ClO4- with PhMgCl and PhLi is better understood in the light of knowledge about reactions of 1a-e.The comparative simplicity of reaction of Th+ClO-, with Ph2Hg is also made clearer.
- Boduszek, Bogdan,Shine, Henry J.,Venkatachalam, T. Krishnan
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p. 1616 - 1626
(2007/10/02)
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- The effect of the nature of the amine leaving group on the nature of the E2 transition state for the reaction of 1-phenylethylammonium ions with sodium ethoxide in ethanol
-
To investigate the effect of the leaving group on the elimination reaction of 1-phenylethylammonium ions with sodium ethoxide in ethanol at 60 deg C, the reaction of seven different quaternary ammonium salts and their β-deuterated analogues with trimethylamine, N-methylpiperidine, N-methyldiethylamine, triethylamine, N,N-dimethylbenzylamine, tripropylamine, and N,N-diethylbenzylamine as leaving groups has been studied.In all cases the elimination, which was shown to proceed via the concerted E2 process, was accompained by competing substitution reactions.Although a significant depedence of the rate of the elimination process on the nature of the leaving group was noted, there was not any linear correlation with the basicity of the amine leaving group.The primary hydrogen-deuterium kinetic isotope effect for the elimination process, (kH/kD)E, was found to increase initially with an increase of reaction rate, kHE, for substrates containing the leaving groups trimethylamine, N-methylpiperidine, N-methyldiethylamine, triethylamine, and N,N-dimethylbenzylamine; i.e., (kH/kD)E=5.03, 5.26, 5.40, 5.83, and 5.85, respectively.A further increase in rate, using substrates with tripropylamine and N,N-diethylbenzylamine as leaving groups resulted in a decrease of the magnitude of the hydrogen-deuterium isotope effect; i.e., (kH/kD)E= 5.42 and 4.67, respectively.It is concluded that steric effects mainly determine leaving group ability.As well, it is concluded that the leaving group ability of the amine determines the structure of the E2 transition state.For the reaction of the poorer leaving groups, trimethylamine, N-methylpiperidine, and N-methyldiethylamine, the proton is more than one-half transferred at the transition state while for reaction involving the two best leaving groups, tripropylamine and N,N-diethylbenzylamine, the Cβ-H bond is less than one-half broken at the transition state.The conclusions are considered in the light of the More O'Ferrall-Jencks potential energy surface diagram.Key words: elimination mechanism, transition state, isotope effects, leaving group, quaternary salts.
- Smith, Peter James,Amin, Md.
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p. 1457 - 1467
(2007/10/02)
-
- FLUORINATION WITH XENON DIFLUORIDE, PART XXXV. REACTION WITH GRIGNARD REAGENTS
-
Several Grignard reagents in diethyl ether solution readily react with xenon difluoride at room temperature, the complexity of the reaction course depending on the structure of the reagent.In all cases studied three main types of products, i.e. 1-ethoxy-1-substituted ethane (2), reduced product (3) and dimeric product (4) are formed.In the case of dodecyl magnesium bromide (1a), 2-ethoxydodecane (2a), decane (3a) and eicosane (4a) formed represent 98percent of products formed, with 2percent of the reaction mixture containing at least up to seven unidentified products, while with benzyl magnesium bromide (1b), the three main products 2b, 3b, and 4b represent 80percent of the reaction mixture, the remaining 20percent containing up to nine products with benzyl bromide being the main side product.The complexity of the reaction increases even more in the case of phenyl magnesium bromide, where 2c, 3c and 4c represent only 70percent of products formed, the remaining 30percent consisting of up to 21 products with the following being identified: bromobenzene, bromobiphenyl, 1,1-bromo-1-phenylethane, α-bromo and α,α-dibromoacetophenone, and 1,1-diphenyl-2-bromoethene.
- Bregar, Zvonko,Stavber, Stojan,Zupan, Marko
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p. 187 - 194
(2007/10/02)
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- ENHANCED NUCLEOPHILE SELECTIVITY IN THE PHOTOADDITION TO STYRENE. COMPARISON WITH THE THERMAL ADDITION
-
The reactivity-selectivity properties of the sec-phenethyl carbenium ion and its analogues have been examined in binary-aqueous solutions of alcohols (ROH; R = Me, Et, CF3CH2, n-Bu, t-Bu, n-Pr, i-Pr), acetic acid, and in solutions containig external nucleophiles such as thiophenol, ethanethiol, acetate, and benzenesulfinate.Selectivity (S = k(Nuc)/k(H2O) is observed to be a function of the nucleophile, the ring substituent, thermal or photochemical conditions, irradiation time, and medium acidity.In the case of styrene, the photochemically generated (usually 254 nm, 1 h) species exhibits greater selectivity (up to two orders of magnitude) than its thermal counterpart, generated (usually 80 deg C, 2-4 d) in identical media, particularly in aqueous-rich solvent compositions.A rationale for these differences, supported by fluorescence quenching experiments, and the other effects upon selectivity will be discussed.
- Anderson, Steven W.,Yates, Keith
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p. 2412 - 2421
(2007/10/02)
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- Gas-Phase Wittig Rearrangement of Carbanions Derived from Benzyl Ethers
-
The CA mass spectra of ions PhC-HOR and Ph(R)CH-O- (R = alkyl and phenyl) are very similar, suggesting that the Wittig rearrangement PhC-HOEt -> Ph(Et)CH-O- occurs in the gas phase.Major fragmentation can be interpreted in terms of 1,2-elimination of groups from the Wittig product ion.For example, 2H labeling of PhC-HOEt and Ph(Et)CH-O- show that the major processes produce Me-CH=CH-O- + C6H6 and (C6H4)-CHO + C2H6, with the latter process involving prior scrambling of phenyl hydrogens.An analogous process, Ph2CH-O- -> (C6H4)-CHO + C6H6 gives the major peak in the spectrum of "PhC-HOPh".
- Eichinger, Peter C. H.,Bowie, John H.,Blumenthal Thomas
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p. 5078 - 5082
(2007/10/02)
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- THE REACTION OF PHENYLMAGNESIUM BROMIDE WITH DIETHYL ETHER DURING GRIGNARD PREPARATION
-
To determine the Grignard products generated during the preparation of phenylmagnesium bromide in peroxide-free ether, the prepared compound was quenched with H2O or D2O and the products quantitatively determined by gas chromatography and gas chromatograp
- Jones, Louis A.,Kirby, Suzanne L.,Kean, David M.,Campbell, Gary L.
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p. 159 - 170
(2007/10/02)
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- Solvomercuration-Demercuration. 12. The Solvomercuration-Demercuration of Olefins in Alcohol Solvents with Mercuric Trifluoroacetate--An Ether Synthesis of Wide Generality
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Studies on the solvomercuration-demercuration (SM-DM) of olefins in methyl, ethyl, isopropyl, and tert-butyl alcohols with mercuric trifluoroacetate have been extended. 1-Dodecene undergoes the SM-DM sequence with typical results for a monosubstituted olefin.Cyclopentene similarly exhibited behavior characteristic of a 1,2-disubstituted olefin in methanol, ethanol, and 2-propanol, giving high yields, >90percent of the corresponding ethers.However, in tert-butyl alcohol, the yields of ether were lower than normal and decreased somewhat with time. 2-Methyl-1-butene gives >90percent yields of the Markovnikov methyl ether.On the other hand, the yields of ethyl, isopropyl, and tert-butyl ethers are lower and decrease with time.Major improvements in yields, however, are possible by lowering the reaction temperature from room temperature to 0 deg C.Cyclooctene, surprisingly, behaves more like a tri-, tetra-, or isosubstituted olefin than a 1,2-disubstituted olefin.The yields of cyclooctyl methyl ether are >90percent and do not decrease with time.However, yields of the ethyl, isopropyl, and tert-butyl ethers are lower and drop with time.Again, lowering the reaction temperature from room temperature to 0 deg C markedly improves the yields of the cyclooctyl ethers.These results, coupled with those of a previous study, clearly reveal the exceptional superiority of mercuric trifluoroacetate for the SM-DM of olefins in alcohol solvents.
- Brown, Herbert C.,Kurek, Joseph T.,Rei, Min-Hon,Thompson, Kerry L.
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p. 1171 - 1174
(2007/10/02)
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- REACTIVITY OF RCu,BF3 AND R2CuLi,BF3 TOWARDS THE ETHER LINKAGE. EPOXIDES, ACETALS AND ORTHOFORMATES
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The association of BF3 to organocopper and cuprate reagents increases dramatically their reactivity towards epoxides.The same reagents cleave acetals to afford the product of substitution of one alkoxy group, whereas orthoformates lead to acetals under co
- Ghribi, A.,Alexakis, A.,Normant, J. F.
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p. 3075 - 3078
(2007/10/02)
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- Solvomercuration-Demercuration. 11. Alkoxymercuration-Demercuration of Representative Alkenes in Alcohol Solvents with the Mercuric Salts Acetate, Trifluoroacetate, Nitrate, and Methanesulfonate
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The alkoxymercuration-demercuration of seven representative olefins with the mercuric salts acetate, trifluoroacetate, nitrate, and methanesulfonate, in methyl, ethyl, isopropyl, and tert-butyl alcohols was examined.Mercuric acetate was effective only in methanol and ethanol.On the other hand, mercuric trifluoroacetate was effective in all four solvents, giving in most cases high yields of the corresponding ethers.Both mercuric nitrate and mercuric methanesulfonate were effective in methanol, ethanol, and 2-propanol.However, in several cases poor selectivity for the ether was observed, as evidenced by the formation of significant amounts of side products.Both electronic and steric effects are important factors in the reaction.Moreover, the structure of the olefin has a pronounced effect, both on the types of oxymercurials formed and on their stability to the reaction conditions.
- Brown, Herbert C.,Kurek, Joseph T.,Rei, Min-Hon,Thompson, Kerry L.
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p. 2551 - 2557
(2007/10/02)
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- Elaboration of α-Substituted Benzyl Ethers and Sulphides by Suppression of the Wittig and Related Rearrangements
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Co-ordination of benzyl alkyl ethers and sulphides to chromium tricarbonyl allows α-substitution via the corresponding α-carbanions to be achieved by suppression of the Wittig and related rearrangements.
- Davies, Stephen G.,Holman, Nicholas J.,Laughton, Charles A.,Mobbs, Bryan E.
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p. 1316 - 1317
(2007/10/02)
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- Kinetics and Mechanism of Nucleophilic Displacements with Heterocycles as Leaving Groups. Part 10. Reactions of s-Alkyl Primary Amines with Pyryliums
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2,4,6-Triphenylpyrylium with s-alkylamines gives isolatable pyridiniums (which undergo SN2 substitution with nucleophiles and elimination to olefins). 2,4,6-triphenylpyrilium with 1-phenylethylamine and α-phenylbenzylamine forms the corresponding carbonium ions which may be trapped by nucleophiles.Isolated 1-cycloalkylbenzoquinoliniums (2) solvolyse by the SN1 mechanism (for five-, six- and seven-membered rings): for the cyclobutyl case an Sn2 reaction is also found.
- Katritzky, Alan R.,Marquet, Jorge,Lloyd, Jeremy M.,Keay, James G.
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p. 1435 - 1442
(2007/10/02)
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- Reaction of Acetals with Grignard Reagents
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The reaction of dialkyl acetals derived from α,β-unsaturated aldehydes with Grignard reagents using TiCl4 in THF afforded the cross coupling products, allyl ethers, in high yields.The TiCl4-promoted reaction of alkyl 2,4-dichlorophenyl acetals, synthesized from 3,4-dihydro-2H-pyran or ethyl vinyl ether and 2,4-dichlorophenol, with Grignard reagents in THF at low temperature afforded the corresponding unsymmetrical ethers in high yields.When alkyl 2,4-dichlorophenyl acetals, synthesized from aromatic aldehyde or vinyl ethers and 2,4-dichlorophenol, were treated with Grignard reagents in benzene or toluene at room temperature in the absence of TiCl4, the cross coupling reaction took place and the corresponding ethers were isolated in good yields.
- Ishikawa, Hiroshi,Mukaiyama, Teruaki,Ikeda, Shigeru
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p. 776 - 780
(2007/10/02)
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- Mercury-assisted solvolyses of alkyl halides. Simple procedures for the preparation of nitrate esters, acetate esters, alcohols and ethers
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The reactions of a wide variety of alkyl halides with mercury(I) and/or (II) nitrate in 1,2-dimethoxyethane, mercury(II) acetate in acetic acid, aqueous mercury(II) perchlorate, and mercury(II) perchlorate in alcohol solvents have been investigated; as a result, simple high yield procedures for the conversion of alkyl halides into the corresponding nitrate esters, acetate esters, alcohols and ethers have been developed.
- McKillop,Ford
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p. 2467 - 2475
(2007/10/05)
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- Sodium borohydride reduction of alkoxythallated compounds of olefins
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Alkaline NaBH4 reduction of alkoxythallated compounds of olefins gives a mixture of the parent olefins, alkyl ethers, and dialkylthallium compounds; hydrogen for replacement of thallium arises from the solvent and not from NaBH4.
- Uemura, Sakae,Tabata, Akira,Okano, Masaya
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p. 517 - 518
(2007/10/12)
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