51440-56-3Relevant academic research and scientific papers
A step forward in solvent knitting strategies: Ruthenium and gold phosphine complex polymerization results in effective heterogenized catalysts
Valverde-González, Antonio,Marchal, Gwendoline,Maya, Eva M.,Iglesias, Marta
, p. 4552 - 4560 (2019/09/09)
Porous polymers based on ruthenium and gold triphenylphosphine complexes (KPhos(Ru), KPhos(Ru)Bi, KPhos(AuCl) and KPhos(AuNTf2)) were prepared via a cost-effective solvent knitting method with [RuHClCO(PPh3)3] or AuXPPh3 (X = Cl, NTf2) as single monomers or combined with biphenyl, which represents a further approach to obtain heterogenized catalysts. The resulting materials mainly preserve the metal coordination environment of their parent complexes, are stable up to 350 °C and have reasonable surface areas (250-300 m2 g-1 for KPhos(Ru)-polymers). KPhos(Ru)s selectively catalyze the imination of alcohols in the presence of base and the results for KPhos(Au)s show they are effective for the intermolecular hydration and hydroamination of alkynes. These materials can be reused several times without significant loss of activity. This novel and simple method affords heterogenized catalysts that combine the reactivity and selectivity of their homogeneous counterparts with the stability and reusability of a heterogeneous framework.
A marcus treatment of rate constants for protonation of ring-substituted α-methoxystyrenes: Intrinsic reaction barriers and the shape of the reaction coordinate
Richard, John P.,Williams, Kathleen B.
, p. 6952 - 6961 (2008/02/09)
Rate and equilibrium constants were determined for protonation of ring-substituted α-methoxystyrenes by hydronium ion and by carboxylic acids to form the corresponding ring-substituted α-methyl α-methoxybenzyl carbocations at 25°C and I = 1.0 (KCl). The thermodynamic barrier to carbocation formation increases by 14.5 kcal/mol as the phenyl ring substituent(s) is changed from 4-MeO- to 3,5-di-NO2-, and as the carboxylic acid is changed from dichloroacetic to acetic acid. The Bronsted coefficient a for protonation by carboxylic acids increases from 0.67 to 0.77 over this range of phenyl ring substituents, and the Bronsted coefficient β for proton transfer increases from 0.63 to 0.69 as the carboxylic acid is changed from dichloroacetic to acetic acid. The change in these Bronsted coefficients with changing reaction driving force, ?α/?ΔG°av = ?β/ ?ΔG°av = 1/8Λ = 0.011, is used to calculate a Marcus intrinsic reaction barrier of Λ = 11 kcal/mol which is close to the barrier of 13 kcal/mol for thermoneutral proton transfer between this series of acids and bases. The value of α = 0.66 for thermoneutral proton transfer is greater than α = 0.50 required by a reaction that follows the Marcus equation. This elevated value of β may be due to an asymmetry in the reaction coordinate that arises from the difference in the intrinsic barriers for proton transfer at the oxygen acid reactant and resonance-stabilized carbon acid product.
Regiospesific Synthesis of Polysubstituted Phenols via the Palladium-Catalyzed Enyne-Diyne [4 + 2] Cross-Benzannulation Pathway
Gevorgyan, Vladimir,Quan, Long Guo,Yamamoto, Yoshinori
, p. 1244 - 1247 (2007/10/03)
An efficient method for the synthesis of polysubstituted phenols via the consecutive palladium-catalyzed enyne-diyne [4 + 2] cross-benzannulation reaction and subsequent deprotection step was developed. In all cases, the reactions proceeded in a regiospecific manner affording the corresponding polysubstituted phenols in good overall yields. It was shown that a more useful one-pot methodology could be applied to the synthesis of polysubstituted phenols 4a-e. The synthetically useful p-methoxyphenylacetylene 13 and its monosilylated derivative 12 were smoothly prepared via exhaustive or partial desilylation of bis-silylated aromatic adduct 8c, respectively.
Reactivity and selectivity in the oxidation of styrene derivatives, II studies on the oxidation of p-substituted α-methylstyrenes
Suprun, Wladimir
, p. 231 - 237 (2007/10/03)
The liquid phase oxidation of p-substituted (Br-, Cl-, t-Bu-, MeO-, CF3-) α-methylstyrenes and of α,p-dimethoxystyrene with pure oxygen was investigated in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 65-125°C. The product yields were determined gaschromatographically. The differences of the activation energies of the epoxide formation and the parallel reactions amount to 19-48 kJ/mol. The epoxide selectivity increases with increasing temperature and concentration of olefine. The relative chain propagation constants kp (C=C) were determined by competitive oxidation with cumene. The kp(C=C) values of p-substituted α-methylstyrenes can be correlated by the Hammett equation with both σ and σ+ substituent constants.
THERMODINAMYCS OF THE ISODESMIC ENOL-TO-METHYL ENOL ETHER EQUILIBRIUM IN WATER
Toullec, Jean,El-Alaoui, Mohiedine,Kleffert, Pascal
, p. 1889 - 1892 (2007/10/02)
ΔGo values for the isodesmic equilibrium between substituted acetophenone enols and corresponding methyl enol ethers are calculated from previously reported data on equilibrium constants for keto-enol tautomerism and for enol ether formation from ketones.These values agree with those expected from literature data on analogous alcohol-ether isodesmic systems.
Carbonyl Methylenation Using a Titanium- Aluminum (Tebbe) Complex
Pine, Stanley H.,Pettit, Robert J.,Geib, Gregory D.,Cruz, Susana G.,Gallego, Claudio H.,et al.
, p. 1212 - 1216 (2007/10/02)
The titanium-aluminum (Tebbe) complex is shown to be an effective methylenating agent for a variety of carbonyl groups.The reaction is unique in that the carbonyl groups of carboxylic acid derivatives are readily methylenated.Thus vinyl enol ethers are prepared from esters and enamines are formed from amides.The complex provides a method for methylenating hindered or base sensitive ketones that is advantageous to the Wittig reagent.Selective methylenation of dicarbonyl compounds is also accomplished.
The Allopolarization Principle and its Applications, IV. Substituent Effects in the Methylation of Enolate Anions
Gompper, Rudolf,Vogt, Hans-Hubert
, p. 2866 - 2883 (2007/10/02)
The ratio of O- and C-methylated products in the reaction of the sodium salts of acetophenones 1, propiophenones 3, phenylacetones 5, β-dicarbonyl compounds 12, α-cyanocarbonyl compounds 13, acetaldehyde, propionaldehyde, and diethylketone with dimethyl sulfate, methyl iodide, and trimethyl phosphate in HMPTA has been determined with regard to the effect of substituents.In some cases the influence of solvents, concentration and temperature has also been studied.
