65483-84-3Relevant academic research and scientific papers
Chlorophosphines as auxiliary ligands in ruthenium-catalyzed nitrile hydration reactions: Application to the preparation of β-ketoamides
González-Fernández, Rebeca,González-Liste, Pedro J.,Borge, Javier,Crochet, Pascale,Cadierno, Victorio
, p. 4398 - 4409 (2016/07/06)
The catalytic hydration of nitriles into amides, in water under neutral conditions, has been studied using a series of arene-ruthenium(ii) complexes containing commercially available chlorophosphines as auxiliary ligands, i.e. compounds [RuCl2(η6-p-cymene)(PR2Cl)] (R = aryl, heteroaryl or alkyl group). In the reaction medium, the coordinated chlorophosphines readily undergo hydrolysis to generate the corresponding phosphinous acids PR2OH, which are well-known "cooperative" ligands for this catalytic transformation. Among the complexes employed, best results were obtained with [RuCl2(η6-p-cymene){P(4-C6H4F)2Cl}]. Performing the catalytic reactions at 40 °C with 2 mol% of this complex, a large variety of organonitriles could be selectively converted into the corresponding primary amides in high yields and relatively short times. The application of [RuCl2(η6-p-cymene){P(4-C6H4F)2Cl}] in the preparation of synthetically useful β-ketoamides is also presented.
Acidity and tautomerism of β-keto esters and amides in aqueous solution
Bunting, John W.,Kanter, James P.
, p. 11705 - 11715 (2007/10/02)
The pH-rate profiles for the keto-enol tautomerization of 17 β-keto esters and amides (RCOCH2COX: R = methyl; phenyl; 2-, 3-, and 4-pyridyl; 3(and 4)-(N-methylpyridinio); X = OCH3, OC2H5, NH2, or N(CH3)2) have been measured by stopped-flow spectrophotometry in aqueous solution (ionic strength 0.1, 25 °C) over the range pH = 2-12. Analysis of these profiles gives the microscopic rate constants for ketonization and enolization of each of these species in these aqueous solutions. Analysis of the pH dependence of the buffer catalysis for the general-acid-catalyzed protonation of these enolate conjugate bases allowed the evaluation of paE for the deprotonation of each enol species. In combination with pKaeq, these data in turn allow the calculation of the acidities of the keto tautomers (pKaK) and the equilibrium constants for enolization (KE = [enol]/[keto] ). In all cases, both the keto and enol tautomers of the amides are more acidic than the corresponding ester derivatives. The equilibrium enol/keto ratios (KE) were found to decrease in the order: 2-pyridyl > 4-pyridyl > 3-pyridyl > 4-(N-methylpyridinio) > 3-(N-methylpyridinio) > methyl ≈ phenyl for both β-keto esters and amides. A simple linear correlation between pKaE and pKaKwas observed for these series of β-keto esters and amides. Bronsted plots of second-order rate constants for deprotonation of the keto tautomer as a function of keto tautomer acidity were found to be linear, with a values in the range 0.37-0.54 for hydroxide ion, acetate ion, and several amine bases. However, the "water-catalyzed" reaction is unusual with Br?nsted α = -0.17. This α value is only readily explicable in terms of a combined general acid + general base catalysis involving two water molecules for the equilibration of the keto tautomer and the neutral enol species.
