Investigation of the intramolecular hydrogen bond of a series of carbalkoxyl derivatives of ?-dicarbonyl compounds by the PMR method

(Het)aroylpyruvic acids and their derivatives as promising building blocks for organic synthesis

“…According to 1 H NMR data, the 3-unsubstituted (H)APA 4, their esters 2 and amides 6 exist in solution as enols. 81,99,100 The enol structure of the benzoylpyruvic acid 4a has also been confirmed by X-ray diffraction analysis. 101 Only ethyl 4-(3-indolyl)-2,4-dioxobutanoate in DMF-d 7 is a mixture of ketone and enol tautomers in a ratio of *1 : 1.…”

Fluorine-containing 2,4-dioxo acids in the synthesis of heterocyclic compounds

“…As for enolisation, the tautomerism of nonfluorinated analogues of dioxo esters 1 has been reported in a series of publications. Thus 1 H NMR spectral studies demonstrated 28 that aroylpyruvates exist mainly as enols. It was also concluded 28 that the intramolecular hydrogen bond in the b-dicarbonyl fragment of the molecule is strengthened as the electron-accepting ability of substituents increases.…”

Synthesis and Antimicrobial Activity of β-N-(Benzoyl)Hydrazides of 4-Aryl-2-hydroxy-4-oxo-butenoic (Aroylpyruvic) Acids

“…Similar to other aroylpyruvic acid derivatives, the new hydrazides in ethanol solutions exhibit cherry-red coloration on interaction with ethanol solutions of iron(III) chloride. This color reaction is indicative of the presence of enol hydroxy groups [6].…”