An LFER study of the protolytic equilibria of 4-aryl-2,4-dioxobutanoic acids in aqueous solutions

Abstract

The protolytic equilibria of 13 4-aryl-2,4-dioxobutanoic acids (ADKs) were spectrophotometrically studied in aqueous solutions in the pH range 1-9 at 25??1??C and an ionic strength of 0.1 mol l (NaCl), with the exception of the 4-OH-derivative which was also potentiometrically studied in the pH range 7-10 at 25??1??C and an ionic strength of 0.1 mol l (NaCl). In solution, the compounds simultaneously exist in one diketo and two enolic forms; therefore, the determined acidity constants (pZ 1.87-2.29, pK 6.63-8.13 and pK(4-OH-) 9.52) represent system macro constants. The H-NMR spectrum of the parent compound (4-phenyl-2,4-dioxobutanoic acid) (25??C, pD 5.0) proved the existence of all tautomeric forms. Using the extended Hammett relation, the determined pK values were correlated with literature ?? values. The predicted pK values were in fair accordance with the experimentally observed ones. Molecular, monoanionic and dianionic forms of the parent compound were optimized by the semi-empirical molecular orbital PM6 method using the implicit water solvation model (COSMO). The obtained geometries were used to explain the quality of the LFER models

Aryldiketo Acids Have Antibacterial Activity Against MDR Staphylococcus aureus Strains: Structural Insights Based on Similarity and Molecular Interaction Fields

“…The synthesis and characterisation of 1-7, 13-19 was previously reported. [6,7] Characterisation data for 8-12…”

Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations

“…Synthesis and characterization of 4PDA were already described [20]. The same sample was used in all NMR measurements described herein.…”

“…ADKs simultaneously exist in two enolate forms (Scheme 1, I and III), conformationally locked by the pseudo-ring, and one diketo form (II) having two rotatable bonds responsible for their conformational flexibility [15,17]. As a continuation of our group's work on structureproperty relationships [18][19][20] and biological activities of ADKs [6], we aimed to further explore their tautomeric preferences.…”

Synthesis of 2-amino-5-(2-aryl-2-oxoethylidene)-4-oxo-1H-4,5-dihydrofuran-3-carboxylic acids derivatives by recyclization of 5-arylfuran-2,3-diones under the action of cyanoacetic acid derivatives

“…Compounds 1а-1g were synthesized by the method [26] from the corresponding aroylpyruvic acids obtained by procedures [27,28]. Compounds 1a-1g [26] were described previously, physicochemical constants and spectral characteristics corresponded to published data.…”