- Chemical shifts of phenolic monomers in solution and implications for addition and self-condensation
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Alkali metal counter-cations alter the electron density of phenolates in solution by electrostatic interactions. This change in electron density affects their reactivity toward formaldehyde, hydroxymethylphenols, and isocyanates during polymerization. The electronic perturbation of phenolic model compounds in the presence of alkali metal hydroxides was investigated with 13C and 1H nuclear magnetic resonance in polar solvents relative to non-ionic controls, altering the chemical shifts of the model compounds, thus indicating changes in electron density using the chemical shift as a proxy. These shifts were attributed to Coulombic electrostatic interactions of the counter-cation with the phenolate anion that correlated to hydrated ionic radius and solvent dielectric constants. The predicted relative reaction rates for formaldehyde addition based on electron density ranking from 13C nuclear magnetic resonance of the phenolic models was compared with the literature values. Predictions for condensation reactions of 2- and 4-hydroxymethylphenol from chemical shifts were consistent with published results. The results permit predictions for the reaction of phenolic compounds for the formation of thermosetting polymeric materials. Copyright
- Haupt, Robert A.,Renneckar, Scott
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- Direct lateral metallation using alkali-metal mediated zincation (AMMZn): SiC-H vs.Si-O bond cleavage
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A new application of zincate [(THF)Li(TMP)(tBu)Zn( tBu)] (1) in alkali-metal mediated zincation (AMMZn) is reported by isolating and structurally defining the first intermediates of direct lateral zincation (DlZn) of trimethyl(phenox
- Hevia, Eva,Kennedy, Alan R.,Klett, Jan,McCall, Matthew D.
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scheme or table
p. 3240 - 3242
(2009/12/01)
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- [2+2] and [2+4] type cycloadditions of isocyanates with ynolates
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Ynolates react with isocyanates to give azetidine-2,4-diones via a [2+2] type cycloaddition. The [4+2] type cycloaddition proceeds in the reactions of vinyl isocyanates with ynolates to provide 2-pyridones.
- Shindo, Mitsuru,Harada, Akiko,Matsumoto, Kenji,Shishido, Kozo
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- Proton affinities and aggregation states of lithium alkoxides, phenolates, enolates, β-dicarbonyl enolates, carboxylates, and amidates in tetrahydrofuran
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The proton affinities of the title compounds are represented by their heats of deprotonation, ΔHdep, through reactions with lithium bis(trimethylsilyl)amide, LiHMDS, in tetrahydrofuran at 25°C. Aggregation numbers of the parent acid and of its lithium salt at a concentration of 0.10 M were obtained by vapor-pressure osmometry at 37°C. Lithium phenolates were also studied by conductivity at 25°C. ΔHdeps for 27 oxygen, nitrogen, and carbon acids of varied types correlate fairly well (R = 0.95) with their published pKas in dimethyl sulfoxide although their degrees of aggregation in THF vary from one to over seven. In some cases, the ΔHdep of an acid is strongly dependent on the concentration ratio of LiHMDS to that of the acid's lithium salt at the time of measurement. Aggregation numbers determined by VPO in this report agree with available published values obtained by previous workers using several techniques. There is no obvious relationship between the aggregation number of the lithium salt and the basicity of the corresponding anion as represented by ΔHdep. This observation along with independent evidence for equilibria between monomers, dimers, tetramers, etc. for a number of compounds indicate that there are only small differences between the relative stabilities of different aggregation states. Conductance data for lithium p-nitrophenolate were treated by Wooster analysis, the results of which suggest equilibria between ion triplets, ion pairs, and free ions in THF. The conductance of LiHMDS in this solvent is surprisingly high, and this property was used to demonstrate an interaction between LiHMDS and lithium o-tert-butylphenolate.
- Arnett, Edward M.,Moe, Kevin D.
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p. 7288 - 7293
(2007/10/02)
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- A method for the determination of the degree of association of organolithium compounds in liquid ammonia
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A method for carrying out cryoscopy in liquid ammonia is presented.The degrees of association of some organolithium compounds in liquid ammonia have been determined.
- Besten, Remco den,Harder, Sjoerd,Brandsma, Lambert
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p. 153 - 159
(2007/10/02)
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- Interaction of alkoxides. XVIII. Utilitization of the complex base from alkyllithium and potassium alkoxides in the dimetallation of phenol, thiophenol, o-, m- and p-cresol
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Successful O- and ortho-ring metallation of phenol and side chain metallation in o-cresol has been achieved by use of a mixture of two molar equivalents of n-butyllithium, one molar equivalent of potassium t-butoxide and two molar equivalents of N,N,N',N'-tetramethylethylene diamine in hexane.Poor results were obtained with m-cresol, thiophenol and p-cresol. m-Cresol was effectively dimetallated with a mixture of two molar equivalents of tBuOK and two molar equivalents of nBuLi*TMEDA.The effectiveness of another type of complex base based on 2-ethylhexyllithium (EhexLi) and potassium alkoxides has been also investigated, especially in respect of the influence of the concentration and the ctructure of the alkoxide used.With a complex base from EhexLi and 3 equivalents of potassium 3-methyl-3-pentoxide phenol was successfuly dimetallated even in the absence of TMEDA.Thus, the enhanced reactivity of a complex base containing a higher concentration of a more branched potassium alkoxide over that of previously used complex bases has been confirmed.
- Andringa, H.,Verkruijsse, H.D.,Brandsma, L.,Lochmann, L.
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p. 307 - 314
(2007/10/02)
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- Template Effects. 4. Ion Pairing of Aryloxide Ions with Alkali Cations in 99percent Me2SO: Influence on the Rate of Formation of Benzo-18-crown-6 and of Other Williamson-Type Reactions
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The effect of alkali metal ions on the rate of formation of benzo-18-crown-6 in 99percent Me2SO by cyclization of the conjugate base of o-hydroxyphenyl 3,6,9,12-tetraoxa-14-bromotetradecyl ether has been quantitatively accounted for according to a scheme involving separate contributions from free (ki) and cation-paired (kip) phenoxide ion.The study has included several additional intra- and intermolecular alkylations of phenoxide ions as reference reactions to provide a set of 25 equilibrium constants for the association of five different phenoxides with the five alkali cations.Both Coulombic interaction and coordination with the neutral oxygen donors are important in determining ion pair stability, but the order in all cases is dominated by Coulombic interaction.This suggests contact interaction in the phenoxide-cation pairs, which is also consistent with evidence from the UV spectra.Whereas the rate of formation of B18C6 is depressed by Li+ (kip/ki + (kip/ki = 100).In contrast, in the reference reactions the ion pairs with the alkali are either negligibly reactive or much less reactive than the free anions.The association constants of the alkali cations with B18C6 have been determined under the same conditions.A comparative analysis of the extent of interaction of the cations with the reactant, transition state, and reaction product of the crown ether forming reaction shows that the transition state binds cations more strongly than the reactant or reaction product and reveals that cation interaction with both the negative charge and the neutral donors bear significant contribution to the stability of the ion pair transition state.A rationale for the template effect is presented in terms of proximity effects and chemical effects arising from interaction of the cation with the nucleophilic site of the reactant.
- Illuminati, Gabriello,Mandolini, Luigi,Masci, Bernardo
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p. 555 - 563
(2007/10/02)
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- Novel 2-aminomethyl-4-,6-dihalogenphenol derivatives and methods for the preparation thereof
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2-AMINOMETHYL-4,6-DIHALOGENPHENOL DERIVATIVES AND SALTS THEREOF WITH PHYSIOLOGICALLY ACCEPTABLE ACIDS OR BASES HAVING THE FORMULA: STR1 wherein X is the same halogen in both positions, R1 is a hydrogen atom or a lower alkyl group, R2 is an alkyl, cycloalkyl, aryl or aralkyl group, or R1 and R2 together with the nitrogen atom may form a saturated heterocyclic ring, which ring may be interrupted by an oxygen, nitrogen or sulfur atom, R3 is a hydrogen atom, an alkyl, alkoxyalkyl, carboxyalkyl, carbamylalkyl, aralkyl, acyl or sulfonyl group or a base radical, e.g. an alkali metal atom, and R3 " is a cyanoalkyl, hydroxyalkyl, carbalkoxy-alkyl, N,N-dialkylcarbamyl, N-alkylcarbamyl-alkyl or N,N-dialkylcarbamylalkyl group, are useful as diuretics and saluretics; some derivatives possess secretolytic activity.
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- Novel 2-amino methyl-4,6-dihalogenphenol derivatives and methods for the preparation thereof
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2-AMINOMETHYL-4,6-DIHALOGENPHENOL DERIVATIVES AND SALTS THEREOF WITH PHYSIOLOGICALLY ACCEPTABLE ACIDS OR BASES HAVING THE FORMULA: STR1 wherein X is the same halogen in both positions, R1 is a hydrogen atom or a lower alkyl group, R2 is an alkyl, cycloalkyl, aryl or aralkyl group, or R1 and R2 together with the nitrogen atom may form a saturated heterocyclic ring, which ring may be interrupted by an oxygen, nitrogen or sulfur atom, R3 is a hydrogen atom, an alkyl, alkoxyalkyl, carboxyalkyl, carbamylalkyl, aralkyl, acyl or sulfonyl group or a base radical, e.g. an alkali metal atom, and R3 " is a cyanoalkyl, hydroxyalkyl, carbalkoxy-alkyl, N,N-dialkylcarbamyl, N-alkylcarbamyl-alkyl or N,N-dialkylcarbamylalkyl group, are useful as diuretics and saluretics; some derivatives possess secretolytic activity.
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