- EFFECT OF THE NATURE OF SOLID METAL FLUORIDES ON THE ALKYLATION KINETICS OF CH-ACIDS IN THE PRESENCE OF ONIUM SALTS
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The selective C-alkylation of ethyl 2-methylacetoacetate by prenyl chloride in the presence of solid metal fluorides proceeds at room temperature with yields of from 2.5 to 87.5percent depending on the nature of the deprotonating agent.The alkylation rate increases in going from LiF to CsF.A linear correlation was found between the activation free energy for thealkylation reaction and the crystal lattice energy of the solid metal fluorides.Ion exchange was not observed between tetrabutylammonium chloride and solid KF, CsF, and CaF2 in acetonitrile.The extent of the exchange with KF*2H2O over 10 h did not exceed 6percent.Deprotonation of ethyl 2-methylacetoacetate by the action of the solid metal fluorides was not observed.Loss of the CH-acid is found in the presence of an onium salt, which varies upon changing the nature of the deprotonating agent; LiF ca.NaF ca.KF (30percent), RbF (54percent), CsF (90percent), CaF2 (35percent).
- Esikova, I. A.
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- Anion recognition by a macrobicycle based on a tetraoxadiaza macrocycle and an isophthalamide head unit
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(Chemical Equation Presented) A macrobicycle formed by a tetraoxadiaza macrocycle containing a dibenzofuran (DBF) spacer and an isophthalamide head unit, named DBF-bz, was used as receptor for anion recognition. The molecular structure of DBF-bz was estab
- Bernier, Nicolas,Carvalho, Silvia,Li, Feng,Delgado, Rita,Felix, Vitor
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- The First Triangular Trinuclear Cluster Compounds of Molybdenum with Nine Cluster Electrons: 1-n, n = 1-3
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The first four M3X13 type molybdenum triangular trinuclear cluster compounds with nine cluster electrons are described in this paper: (Bu4N)2*Me2CO (1), (Bu4N)*2THF (2), (3), and *THF (4).The first three compounds were obtained by chemical reduction of (Bu4N)*Me2CO, and the last one was prepared as a byproduct from a reaction mixture containing MoCl3(THF)3, Na/Hg, S, NaOAc, and PMe3.In all four compounds, each metal atom has the formal oxidation state + 3 and there are nineelectrons for the metal cluster.Physical measurements indicated that these compounds are paramagnetic and have one unpaired electron, which is in good accord with theoretical calculations.In compound 1 the metal-metal bond distances are 2.617 (1), 2.598 (1), and 2.598 (1) Angstroem.The crystals belong to the space group Cc with Z = 4.The unit cell dimensions are a = 22.600 (3) Angstroem, b = 12.031 (2) Angstroem, c = 23.110 (4) Angstroem, β = 113.51 (1) deg, V = 5762 (2) Angstroem3.In compound 2, the metal-metal bond distances are 2.637 (1), 2.573 (1), and 2.567 (1) Angstroem.It crystallized in the space group P21/c with Z = 4 and the following unit cell dimensions a = 13.419 (3) Angstroem, b = 19.882 (5) Angstroem, c = 18.630 (5) Angstroem, β = 96.27 (2) deg, V = 4940 (2) Angstroem3.Compound 3 belongs to the space group P21/c with a = 10.381 (3) Angstroem, b = 12.680 (2) Angstroem, c = 19.402 (2) Angstroem, β = 90.09 (1) deg, V = 2553.6 (8) Angstroem3, and Z = 4.The metal-metal bond distances are 2.5878 (5), 2.6117 (5), and 2.5764 (5) Angstroem.Compound 4 forms triclinic crystals in the space group P1 with the following unit cell dimensions a = 10.121 (2) Angstroem, b = 11.013 (2) Angstroem, c = 14.628 (3) Angstroem α = 97.71 (2) deg, β = 93.06 (2) deg, γ = 104.62 (2) deg, V = 1556.9 (6) Angstroem3, and Z = 2.The metal-metal bond distances are 2.597 (1), 2.608 (1), and 2.5673 (9) Angstroem.
- Cotton, F. Albert,Shang, Maoyu,Sun, Zhong Sheng
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- Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Slats. Part 4. Rearrangement of Hydrogen-bonded Ion Pairs of Triethylammonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution
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Rearrangement of triethyl- and tetrabutylammonium salts in chloroform solution has been revealed from the characteristic features of the ν(N+H) bands caused by Fermi resonance interaction.Temperature changes of the i.r. spectra show this process to be reversible.Rearrangement constant K1 and K-1 and enthalpies -ΔH (for some cases only) of this process have been determined by measuring the total integrated intensities of the ν(N+H) bands of complexes which are in equilibrium.K1 values of the tetrabutylammonium salts increase with decreasing hydrogen bonding strength in triethylammonium salts.The measured enthalpies of rearrangement and those calculated from the ν(N+H) bands of hydrogen-bonded complexes studied are in agreement.It has also been shown that tetrabutylammonium salts anions can participate in the rearrangement of hydrogen-bonded ion pairs like the organic bases studied previously.
- Mashkovsky, Alexander A.,Nabiullin, Ahat A.,Odinokov, Stanislav E.
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- Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
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Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
- Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
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supporting information
(2020/03/13)
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- Formal Gold-to-Gold Transmetalation of an Alkynyl Group Mediated by Palladium: A Bisalkynyl Gold Complex as a Ligand to Palladium
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The reaction of [Au(C-C n-Bu)]n with [Pd(η3-allyl)Cl(PPh3)] results in a ligand and alkynyl rearrangement, and leads to the heterometallic complex [Pd(η3-allyl){Au(C-C n-Bu)2}]2 (3) with an unprecedented bridging bisalkynyl-gold ligand coordinated to palladium. This is a formal gold-to-gold transmetalation that occurs through reversible alkynyl transmetalations between gold and palladium. Back and forth! Direct gold-to-palladium and reverse palladium-to-gold alkynyl transmetalations effectively produce a deceptively simple gold-to-gold transfer. The resulting bisalkynyl-gold complexes act as bridging ligands to palladium atoms in an unprecedented structural motive (see scheme).
- Toledo, Alberto,Meana, Isabel,Albéniz, Ana C.
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supporting information
p. 13216 - 13220
(2015/09/15)
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- Distinguishing between pathways for transmetalation in Suzuki-Miyaura reactions
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We report a systematic study of the stoichiometric reactions of isolated arylpalladium hydroxo and halide complexes with arylboronic acids and aryltrihydroxyborates to evaluate the relative rates of the two reaction pathways commonly proposed to account for transmetalation in the Suzuki-Miyaura reaction. On the basis of the relative populations of the palladium and organoboron species generated under conditions common for the catalytic process and the observed rate constants for the stoichiometric reactions between the two classes of reaction components, we conclude that the reaction of a palladium hydroxo complex with boronic acid, not the reaction of a palladium halide complex with trihydroxyborate, accounts for transmetalation in catalytic Suzuki-Miyaura reactions conducted with weak base and aqueous solvent mixtures.
- Carrow, Brad P.,Hartwig, John F.
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supporting information; experimental part
p. 2116 - 2119
(2011/04/23)
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- Synthesis of a C3-symmetric furyl-cyclopeptide platform with anion recognition properties
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A new furyl amino acid derivative was trimerized to give a linear peptide and finally was cyclized. The newly generated cyclopeptide was subjected to a conformational study in order to be considered as a C3-symmetric platform for the ratio nal design of complex receptors. Moreover, the recognition properties towards cyanide, acetate and chloride anions were studied.
- Molina, Lidia,Moreno-Clavijo, Elena,Moreno-Vargas, Antonio J.,Carmona, Ana T.,Robina, Inmaculada
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experimental part
p. 4049 - 4055
(2010/09/10)
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- Encapsulated binding sites - Synthetically simple receptors for the binding and transport of HCl
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We report a receptor with an encapsulated amine/amide binding site, which binds HCl with high affinity in organic media - the rate of HCl transport through an apolar phase is controlled by the degree of encapsulation of the HCl binding site.
- Winstanley, Keith J.,Allen, Sarah J.,Smith, David K.
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scheme or table
p. 4299 - 4301
(2011/03/19)
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- Effect of spacer geometry on oxoanion binding by bis- and tetrakis-thiourea hosts
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Hosts with thiourea groups bind anions by formation of multiple hydrogen bonds. This contribution discusses how spacers linking two or four thiourea groups affect the host affinity and selectivity. While most of the bis-thioureas bind H2PO4- preferentially, the extent of selectivity over chloride, acetate, and H2AsO4- is determined by the size of the binding cavity. A tetrakis-thiourea is shown to exhibit a unique H2AsO4- selectivity, and the discrimination of chloride is enhanced by specific solvation in dimethyl sulfoxide.
- Leung, Annie N.,Degenhardt, Dave A.,Bühlmann, Philippe
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p. 2530 - 2536
(2008/09/18)
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- ACID DEACTIVATION OF A NUCLEOPHILE IN THE PHASE-TRANSFER PHENOLYSIS OF CYCLOPHOSPHAZENES AND ITS MECHANISM UNDER HOMOGENEOUS CONDITIONS
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The reactions of tetraalkylammonium salts of 2,4-dinitrophenol (ArO-Q+) with the cyclic trimer of phosphonitrile chloride were studied in a two-phase system of a buffer solution and benzene and in a homogeneous system modeling the conditions of the organic phase. In a two-phase system the aryloxide ion, while being incompletely ionized in the aqueous phase, is extracted into the organic phase together with the neutral form of the phenol, which results in the inhibition of the reaction of monoaryloxyphosphazene formation. The reason lies in the deactivation of the nucleophile as a result of the formation of less reactive complexes with an H bond between the anion and/or the ion pair ArO-Q+ and the proton donor (ROH) contained in the organic phase. On the basis of the kinetic relations and of the results of a study of the equilibrium processes it was found that in the case of strong proton donors (phenols) complexes of the anion and of the ion pair ArO-Q+ with a composition of 1:1 react with the substrate, but in case of weak donors (alcohols) an ion pair not bound into a complex and associations with the anion with compositions of 1:1 and 1:2 react. The reactivity of the complexes of composition 1:1 is thus proportional to the values of the constants of complex formation with ROH, and the inhibiting action of the latter is governed by a single correlation equation without regard to the type of the H-bond acceptor and to the nature of ROH. On the basis of the quantum-chemical calculations it was supposed that the ambiguous effect of ROH on the nucleophilicity of the anions and of the ArO-Q+ ion pairs is determined by the differences in specific solvation between the transition states of the reactions involving these forms of the reagent.
- Afon'kin, A. A.,Shumeiko, A. E.,Popov, A. F.
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p. 457 - 463
(2007/10/02)
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- PHASE-TRANSFER PHENOLYSIS OF CYCLOPHOSPHAZENES DURING NONCOMPETITIVE EXTRACTION OF THE IONIC REACTANT: RATE-LIMITING STAGE AND THE TYPE OF THE DOMINANT NUCLEOPHILE
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We studied the reaction of salts of nitro-substituted phenols with cyclophosphazenes in a diphase system of a borate buffer and an organic solvent.Tetraalkylammonium arylates were found to react with the cyclophosphazenes under phase-transfer conditions as free or associated with H2O ionic pairs and hydrated arylate ions.The dominating role of one nucleophile in the reaction is due to the ability of the arylate salt to dissociate into ions and to associate with H2O.Either the stage of mass transfer of the ionic reactant or the chemical interaction itself can be therate-limiting stage.The factors increasing the ability of the dominant nucleophile to pass into the organic phase and decreasing its reactivity increase the probability that the phase-transfer process goes through a limiting stage of the chemical transformation of the reactant.A mechanism of the phase-transfer catalysis is proposed in which the possibility for the reactions to proceed in the bulk of the organic phase or at the interface is determined by the ratio of the experimentally observed rates of phase transfer of the reactant and of its reaction with the substrate.
- Afon'kin, A.A.,Shumeiko, A.E.,Popov, A.F.
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p. 2097 - 2103
(2007/10/02)
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- Preparation and Reactivities of (η3-1- and 2-Trimethylsiloxyallyl)Fe(CO2)NO Complexes. Intermediates Functioning as Equivalents of β- and α-Acyl Carbocations and Acyl Carbanions
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(η3-1- and 2-Trimethylsiloxyallyl)Fe(CO)2NO complexes were prepared by the reaction of the corresponding siloxyallylic halides with Bu4N.These complexes reacted with both of carbon nucleophiles and carbon electrophiles preferentially at the less hindered sites of the allylic ligands.In these reactions, (η3-1-trimethylsiloxyallyl)Fe(CO)2NO complexes served as synthetically equivalent synthons for both of β-acyl carbocations and β-acyl carbanions and (η3-2-trimethylsiloxyallyl)Fe(CO)2NO complexes as both of α-acyl carbocations and α-acyl carbanions.The stereochemical courses of the reactions are described.
- Itoh, Keiji,Nakanishi, Saburo,Otsuji, Yoshio
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p. 2965 - 2977
(2007/10/02)
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- Preparation and Vibrational Spectra of 13C and 18O Labelled trans-Dioxotetracyanoosmate(VI), (2-)
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Through careful acidification of the aqueous solution of (2-) in the presence of CN(-) or (13)CN(-) with acetic acid, (2-) or (2-) are formed, respectively.The reaction of Os(18)O4 and tetrabutylammonium cyanide with glacial acetic acid in anhydrous methanol yields (2-).The shifts of the infrared and Raman bands of the isotopically labelled complexes are in good agreement with Teller-Redlich calculations.The degenerate E modes, expected for tetragonal symmetry, are split by approx. 15 cm-1, indicating an orthorhombic distortion of the complex ion in the solid state.Therefore, all the observed IR- and Raman frequences are assigned according to point group D2h.For the complex containing an (16)O=Os=(18)O axis, the symmetry is lowered to C2v, and the rule of mutual exclusion is restricted.This results in a weak absorption in the infrared spectrum of the Raman active symmetric OsO stretching vibration and vice versa a weak band in the Raman spectrum for the antisymmetric infrared active mode. - Keywords: trans-Dioxotetracyanoosmate(VI), Isotopic Labeling, IR Spectra, Raman Spectra
- Preetz, W.,Sartori, C.
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- NUCLEOPHILIC SUBSTITUTION AT SULPHUR. COMPLEXES OF SULTONES WITH CHLORIDE AND BROMIDE IONS
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2-Hydroxy-3,5-dinitrotoluene-α-sulphonic acid sultone, 1, reacts with Cl(-) in nitrobenzene or acetonitrile yielding 2-hydroxy-3,5-dinitrotoluene-α-sulphonyl chloride.The reaction proceeds via the formation of an ion-molecule pair.Similar complexes are formed with the corresponding mononitro and unsubstituted sultones, 4 and 5, which do not undergo nucleophilic substitution.The complexes are detected by NMR since the methylene protons of the sultones in the complexes are displaced by more than 1 ppm to lower field because of the adjacent negative charge of the halide ion.
- Gambarotta, Sandro,Isola, Mauro,Senatore, Lucio,Ciuffarin, Ennio
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p. 297 - 300
(2007/10/02)
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