- SNAr reactions of 1-halo-2,4-dinitrobenzenes with alkali-metal ethoxides: Differential stabilization of ground state and transition state determines alkali-metal ion catalysis or inhibition
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A kinetic study on SNAr reactions of 1-halo-2,4-dinitrobenzenes (6a-6d) with alkali-metal ethoxides (EtOM; M = Li, Na, K and 18-crown-6-ether-complexed K) is reported. The plots of pseudo-first-order rate constant (kobsd) vs. [EtOM]
- Yang, Kiyull,Kim, Min-Young,Um, Ik-Hwan
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- The effect of varying the anion of an ionic liquid on the solvent effects on a nucleophilic aromatic substitution reaction
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A variety of ionic liquids, each containing the same cation but a different anion, were examined as solvents for a nucleophilic aromatic substitution reaction. Varying the proportion of ionic liquid was found to increase the rate constant as the mole fraction of ionic liquid increased demonstrating that the reaction outcome could be controlled through varying the ionic liquid. The solvent effects were correlated with the hydrogen bond accepting ability (β) of the ionic liquid anion allowing for qualitative prediction of the effect of changing this component of the solute. To determine the microscopic origins of the solvent effects, activation parameters were determined through temperature-dependent kinetic analyses and shown to be consistent with previous studies. With the knowledge of the microscopic interactions in solution, an ionic liquid was rationally chosen to maximise rate enhancement demonstrating that an ionic solvent can be selected to control reaction outcome for this reaction type.
- Hawker, Rebecca R.,Haines, Ronald S.,Harper, Jason B.
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supporting information
p. 3453 - 3463
(2018/05/23)
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- Rationalising the effects of ionic liquids on a nucleophilic aromatic substitution reaction
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The nucleophilic aromatic substitution reaction between 1-fluoro-2,4-dinitrobenzene and ethanol was examined in a series of ionic liquids across a range of mole fractions. Temperature-dependent kinetic analyses were undertaken to determine the activation parameters for this reaction at the highest mole fraction. As the mole fraction of ionic liquid was increased, the rate constant of the reaction also increased, however the microscopic origin of the rate enhancement was shown to be different between different ionic liquids and also between different solvent compositions. These results indicate a balance between microscopic interactions that result in the observed solvent effects and a qualitative method for analysing such interactions is introduced.
- Hawker, Rebecca R.,Wong, Michaela J.,Haines, Ronald S.,Harper, Jason B.
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supporting information
p. 6433 - 6440
(2017/08/10)
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- NITRATION OF AROMATIC COMPOUNDS
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The present invention provides a process for nitrating aromatic compounds without the need for a solid catalyst and/or any organic solvents and/or any other additives. A typical process includes combining or admixing a nitric acid and an anhydride compound under conditions sufficient to produce a reactive intermediate. The aromatic compound to be nitrated is then added to this reactive intermediate to produce a nitroaromatic compound. The nitroaromatic compound can be substituted with one or more, typically, one to three, and often one or two nitrate (-NO2) groups.
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Paragraph 0048
(2016/08/17)
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- Novel Chloroimidazolium-Based Ionic Liquids: Synthesis, Characterisation and Behaviour as Solvents to Control Reaction Outcome
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Novel ionic liquids containing chlorine atoms on the imidazolium cation were synthesised. The physicochemical properties of these ionic liquids were investigated extensively, including glass transition, melting and decomposition temperatures, density, vis
- Hawker, Rebecca R.,Panchompoo, Janjira,Aldous, Leigh,Harper, Jason B.
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p. 574 - 583
(2016/07/06)
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- Alkali-Metal Ion Catalysis and Inhibition in SNAr Displacement: Relative Stabilization of Ground State and Transition State Determines Catalysis and Inhibition in SNAr Reactivity
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We report here the first observation of alkali-metal ion catalysis and inhibition in SNAr reactions. The plot of kobsd versus [alkali-metal ethoxide] exhibits downward curvature for the reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene with EtOLi, EtONa, and EtOK, but upward curvature for the corresponding reaction with EtOK in the presence of 18-crown-6-ether (18C6). Dissection of kobsd into the second-order rate constants for the reactions with the dissociated EtO- and the ion-paired EtOM (i.e., k EtO - and kEtOM, respectively) has revealed that the reactivity increases in the order EtOLi-+, Na+, and K+ ions but is catalyzed by 18C6 K+ ion. The reactions of 1-(Y-substituted-phenoxy)-2,4-dinitrobenzenes have been proposed to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs after the rate-determining step based on the kinetic result that σo constants exhibit a much better Hammett correlation than σ- constants. Alkali-metal ion catalysis or inhibition has been discussed in terms of differential stabilization of ground-state and transition-state complexes through a qualitative energy profile. A π-complexed transition-state structure is proposed to account for the kinetic results.
- Um, Ik-Hwan,Cho, Hyo-Jin,Kim, Min-Young,Buncel, Erwin
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p. 13337 - 13344
(2016/02/19)
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- Alkali-metal ion catalysis and inhibition in snar reaction of 1-halo-2,4-dinitrobenzenes with alkali-metal ethoxides in anhydrous ethanol
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A kinetic study is reported for SNAr reaction of 1-fluoro-2,4- dinitrobenzene (5a) and 1-chloro-2,4-dinitrobenzene (5b) with alkali-metal ethoxides (EtOM, M = Li, Na, K and 18-crown-6-ether complexed K) in anhydrous ethanol. The second-order rate constant
- Kim, Min-Young,Ha, Gyu Ho,Um
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p. 2438 - 2442
(2014/11/27)
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- Regioselective dinitration of simple aromatics over zeolite Hβ/nitric acid/acid anhydride systems
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Various nitration systems comprising nitric acid, acid anhydride and zeolite H￡] in the absence of solvent are described. Direct double nitration of toluene with a nitric acid, propanoic anhydride and zeolite Hβ system has been developed to give 2,4-dinitrotoluene in 98% yield, with a 2,4-:2,6-dinitrotoluene ratio of 123:1. This system also nitrates activated mono-substituted benzenes (anisole and phenetole) and moderately activated mono-substituted benzenes (ethylbenzene and propylbenzene) to give mainly 2,4-dinitro derivatives. The zeolite can be recovered, regenerated and reused to give almost the same yield as that given when fresh zeolite is used. ARKAT-USA, Inc.
- Smith, Keith,Alotaibi, Mohammad Hayal,El-Hiti, Gamal A.
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p. 107 - 123
(2014/04/17)
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- Highly regioselective dinitration of toluene over reusable zeolite Hβ
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A nitration system comprising nitric acid, propanoic anhydride, and zeolite Hβ has been developed for dinitration of toluene to give 2,4-dinitrotoluene in 98% yield, with a 2,4-:2,6-dinitrotoluene ratio of over 120. This represents the most selective quantitative method for 2,4-dinitration of toluene; the catalyst is reusable, solvent is not needed, and an aqueous work-up is not required.
- Smith, Keith,Alotaibi, Mohammad Hayal,El-Hiti, Gamal A.
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p. 244 - 247
(2013/02/22)
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- Probing the importance of ionic liquid structure: A general ionic liquid effect on an SNAr process
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The effect of a range of ionic liquids, with systematic variations in the cation and anion, on the rate constant of an aromatic substitution process was investigated. Temperature-dependent kinetic data allowed calculation of activation parameters for the process in each solvent. These data demonstrate a generalised ionic liquid effect, with an increase in rate constant observed in each ionic solvent, though the microscopic origins of the rate constant enhancement differ with the nature of the ionic liquid.
- Tanner, Eden E. L.,Hawker, Rebecca R.,Yau, Hon Man,Croft, Anna K.,Harper, Jason B.
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supporting information
p. 7516 - 7521
(2013/11/06)
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- METHODS FOR THE NITRATION OF AROMATIC COMPOUNDS
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According to the invention there is provided a method for the nitration of an aromatic compound including the step of reacting the aromatic compound with nitric acid in the presence of an acid anhydride and an aluminosilicate catalyst, in which the acid anhydride is at least one of: ((CnH2n+1)CO)20, where n is 1 to 4 and the moiety CnH2n+1 can be straight or branched chain; ((CHpClq)CO)20, where p is 0 to 2, q is 1 to 3, and p+q = 3; and oxoiane -2, 5-dione, with the proviso that when the acid anhydride is (CH3CO)20, the aromatic compound is toluene, 2-nitrotoluene or 4-nitrotoluene, and the nitration is performed to produce 2,4-dinitrotoluene.
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Page/Page column 14
(2012/05/04)
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- Synthesis of substituted acetylenes, aryl-alkyl ethers, 2-alkene-4-ynoates and nitriles using heterogeneous mesoporous Pd-MCM-48 as reusable catalyst
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Pd-MCM-48 has been employed as a heterogeneous catalyst for the synthesis of substituted acetylenes via Sonogashira reactions under copper and amine-free reaction conditions. In addition, the catalyst exhibited excellent regioselectivity for primary alcohols towards C-O coupling leading to formation of alkyl-aryl ethers in high yields. A green procedure for the stereoselective synthesis of 2-alkene-4-ynoates and nitriles from the reactions of vic-(E)-diiodoalkenes with activated alkenes has also been demonstrated using Pd-MCM-48 catalyst. The catalyst was easily recovered from the reaction mixture by filtration and reused for at least six times with minimal loss of activity.
- Banerjee, Subhash,Khatri, Hari,Balasanthiran, Vagulejan,Koodali, Ranjit T.,Sereda, Grigoriy
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scheme or table
p. 5717 - 5724
(2011/08/21)
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- Efficient esterification of carboxylic acids and phosphonic acids with trialkyl orthoacetate in ionic liquid
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An operationally simple, inexpensive, efficient, and environmentally friendly esterification of various carboxylic acids, phosphonic acids, and phosphinic acids with triethyl orthoacetate or trimethyl orthoacetate under neutral conditions in a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, was successfully carried out to provide the corresponding ethyl esters or methyl esters in high yields.
- Yoshino, Tomonori,Imori, Satomi,Togo, Hideo
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p. 1309 - 1317
(2007/10/03)
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- Mechanistic study on nitrosation-deaminocyclization of mono-carbamoylated vicinal amino alcohols and diols: a new preparative in situ formation of ethanediazo hydroxide for the ethylation of carboxylates under mild conditions
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While the cyclization of N-carbamoylamino alcohols into oxazolidinones via the activation with NO(1+) underwent smoothly, we found that similar reactions of vicinal diol monocarbamates were very slow. Mechanistic studies by means of time-resolved IR measurements of the former reaction suggested that the initial O-nitrosation was the rate-determining step. Indeed, the introduction of an ethyl group on the nitrogen terminus of diol monocarbamate promoted the desired cyclic carbonate formation. The concomitantly formed ethanediazo hydroxide, the precursor of the protonated form of diazoethane, was evidenced by trapping with p-nitrobenzoic acid as an ethyl ester. The formation of ethyl ester accelerates the reaction in an irreversible manner. Based on an elaboration of the substrates and reaction conditions, 2,3-dimethyl-2,3-butanediol mono-N-ethyl-N-nitrosocarbamate, which is easily prepared in situ from the corresponding ethylcarbamate and t-butyl nitrite, was developed as a new ethylation reagent of various carboxylic acids under mild conditions.
- Suzuki, Masumi,Sugai, Takeshi
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p. 1217 - 1228
(2007/10/03)
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- Relative reactivity of methyl iodide to ethyl iodide in nucleophilic substitution reactions in acetonitrile and partial desolvation accompanying activation
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Through the examination of empirical correlations involving activation parameters for nucleophilic substitution of methyl iodide and of ethyl iodide, nucleophiles have been classified into three series: (1) nucleophiles with two equivalent reaction sites, (2) nucleophiles with a chlorine atom in the para-position, and (3) nucleophiles with a single reaction site. Three types of partial desolvation processes accompanying activation have been deduced on the basis of these classifications. A major factor determining the relative reactivity of methyl iodide to ethyl iodide in the substitution reaction of an anionic nucleophile having a single reaction site in acetonitrile (kMeI/kEtI) is suggested to be partial desolvation around the nucleophilic center on going from reactant to transition-state.
- Kondo, Yasuhiko,Urade, Miyuki,Yamanishi, Yukari,Chen, Xinyu
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p. 1449 - 1454
(2007/10/03)
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- Chemoselective O-methylation of phenols under non-aqueous condition
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Chemoselective O-methylation of substituted phenols takes place in dry. tetrahydrofuran (THF) in the presence of LiOH.H2O and dimethylsulfate (DMS). Quantitative methyl transfer from DMS preserves the atom economy.
- Basak, Anindita,Nayak, Mrinal K.,Chakraborti, Asit K.
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p. 4883 - 4886
(2007/10/03)
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