scholarly journals Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

2017 ◽  
Vol 13 ◽  
pp. 2854-2861 ◽  
Author(s):  
Alexey M Starosotnikov ◽  
Dmitry V Shkaev ◽  
Maxim A Bastrakov ◽  
Ivan V Fedyanin ◽  
Svyatoslav A Shevelev ◽  
...  
Keyword(s):  
Enol Form ◽  
Polar Solvents ◽  
No Donor ◽  
Dicarbonyl Compounds ◽  
Ch Acids ◽  
Electrophilic Character

4-Aza-6-nitrobenzofuroxan (ANBF) reacts with 1,3-dicarbonyl compounds and other CH acids to give carbon-bonded 1,4-adducts – 1,4-dihydropyridines fused with furoxan ring. In the case of most acidic β-diketones, which exist mainly in the enol form in polar solvents, the reactions proceed in the absence of any added base emphasizing the highly electrophilic character of ANBF. The resulting compounds combine in one molecule NO-donor furoxan ring along with a pharmacologically important 1,4-dihydropyridine fragment and therefore can be considered as prospective platforms for the design of pharmacology-oriented heterocyclic systems.

SPECTROSCOPIC STUDIES OF KETO–ENOL EQUILIBRIA: PART 2. ANOMALOUS ULTRAVIOLET ABSORPTION SPECTRA OF SATURATED 1,2-DICYANO ESTERS

1962 ◽  
Vol 40 (12) ◽  
pp. 2272-2277 ◽  
Author(s):  
T. R. Kasturi ◽  
B. N. Mylari ◽  
A. Balasubramanian ◽  
C. N. R. Rao
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Spectroscopic Studies ◽  
Anomalous Behavior ◽  
Enol Form ◽  
Ultraviolet Absorption ◽  
Polar Solvents ◽  
Solvent Dependence

1,2-Dicyano esters show an absorption band around 245 mμ in alcoholic solutions which is not found in non-polar and other polar solvents. This anomalous behavior has been found to be due to the unusual solvent dependence of the equilibrium between the keto and enol forms. The intensity of the absorption band in alcoholic solutions decreases with increase in concentration of the 1,2-dicyano ester, indicating association of the enol form. The keto–enol equilibrium is also found to be sensitive to the substituent R of the alcohol ROH.

Photoisomerization of the enol form of 1,3-dicarbonyl compounds

1977 ◽  
Vol 99 (8) ◽  
pp. 2723-2729 ◽  
Author(s):  
D. Veierov ◽  
T. Bercovici ◽  
E. Fischer ◽  
Y. Mazur ◽  
A. Yogev
Keyword(s):  
Enol Form ◽  
Dicarbonyl Compounds

Tautomerism of Pyrazolidine-3,5-diones. III. Nuclear magnetic resonance spectra

1978 ◽  
Vol 31 (8) ◽  
pp. 1855 ◽  
Author(s):  
M Woodruff ◽  
JB Polya
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Enol Form ◽  
Polar Solvents ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The tautomerism of some N1- and N1,N2-substituted pyrazolidine-3,5-diones has been studied by N.M.R. spectroscopy. The diketo form is the only unambiguously detectable tautomer of N-phenylpyrazolidine-3,5-diones in CDCl3 and (CD3)2SO whereas N-(1H-1,2,4-triazol-5-yl)pyrazolidine- 3,5 diones exist as a mixture of the diketo form with other tautomers. Polar solvents shift the equilibrium towards the keto-enol form; the diketo form is favoured at raised temperatures.

scholarly journals Curcumin analogues for possible cancer treatment A QSAR and partial ordering study

2021 ◽  
Vol 1 (2) ◽  
pp. 001-016
Author(s):  
Lars Carlsen ◽  
Poul Erik Hansen ◽  
Bahjat A Saeed ◽  
Rita S Elias
Keyword(s):  
Cancer Treatment ◽  
Spectroscopic Studies ◽  
Enol Form ◽  
Partial Ordering ◽  
Therapeutic Effects ◽  
Prostate Cancer Treatment ◽  
Polar Solvents ◽  
Curcumin Analogues ◽  
Structure Activity ◽  
Selection Of

The possible effect of curcumin as a potential natural cancer treatment drug has been intensively discussed. In the present study the probabilities of a series of curcumin analogues to possess potential as antineoplastic, prostate cancer treatment and anticarcinogenic agents has been studied theoretically applying a selection of quantitative structure-activity relation and absorption, distribution, metabolism, and excretion (ADME) approaches. From spectroscopic studies it is evident that these compounds can be found in both enol and diketo forms, the former in general the more predominant in non-polar solvents, whereas in polar solvents, like water an increasing amount of the diketo form can be noted. Hence, the probabilities for both the enols and diketo forms to possess the above-mentioned effects were studied. In most cases the enol form shows the highest probabilities for being effective although the differences are not significant. Thus, it is suggested to look at the sum of effects of the keto and the enol forms in relation to the possible therapeutic effects of the compounds here studied.

ChemInform Abstract: PHOTOISOMERIZATION OF THE ENOL FORM OF 1,3-DICARBONYL COMPOUNDS

1977 ◽  
Vol 8 (27) ◽  
pp. no-no
Author(s):  
D. VEIEROV ◽  
T. BERCOVICI ◽  
E. FISCHER ◽  
Y. MAZUR ◽  
A. YOGEV
Keyword(s):  
Enol Form ◽  
Dicarbonyl Compounds

Über Metallalkyl- und -arylverbindungen, 51. Mittlg.* Unsymmetrische Diorganomagnesiumverbindungen. MgRR'(L) und solvensgetrennte Ionenpaare mit R = Me, Et, R' = Cyclopentadienyl, Indenyl, Fluorenyl, Phenylethinyl, L = Tetramethylethylendiamin, Pentamethyldiethylentriamin / On Metal Alkyl and Aryl Compounds, Part 51 Unsymmetrical Diorganomagnesium Compounds. MgRR'(L) and Solvens Separated Ion Pairs with R = Me, Et, R' = Cyclopentadienyl, Indenyl, Fluorenyl, Phenylethynyl, L = Tetramethylethylenediamine, Pentamethyldiethylenetriamine

1994 ◽  
Vol 49 (1) ◽  
pp. 89-99 ◽  
Author(s):  
Heiko Viebrock ◽  
Dirk Abein ◽  
Erwin Weiss
Keyword(s):  
Ion Pairs ◽  
Direct Interaction ◽  
The Other ◽  
Steric Repulsion ◽  
Complicated Structure ◽  
Acid Base ◽  
Polar Solvents ◽  
X Ray ◽  
Ch Acids ◽  
Amine Adducts

Abstract Amine adducts of diorganomagnesium compounds MgR2(L) are soluble in hydrocarbons and therefore valuable synthons for reactions in non-polar solvents. In this way unsymmetrically substituted derivatives MgRR'(L) become available by substituting one organic group by a different carbanion via acid-base reactions, according to eq. (1): R2Mg(L) + HR' -> RR'Mg(L) + HR (1) with HR' being stronger CH-acids than HR. Using the amin adducts R2Mg(L) (R = Me, Et) with chelating amines (L = tetramethyl­ ethylenediamine, TMEDA, pentamethylethylenetriamine, PMDTA) and the strong CH-acids cyclopentadiene, indene, fluorene and alkynes the following compounds have been synthesized and their structures derived by X-ray analyses: MgMe(η3-cyclopentadienyl)(tmeda) (1), MgMe(η3-indenyl)(tmeda) (2), MgMe(η1-fluorenyl)(tmeda) (3), [Mg2Me2(pmdta)2]2+[fluorenyl]−2benzene (4) and [Mg2Et(phenylethynyl)3(tmeda)]2 ∙ benzene (5). It is remarkable, that cyclopentadienyl, indenyl, and fluorenyl ligands have a lower hapticity than η5 to the metal, due to steric repulsion by the other ligands. In 4 the bulky tridentate base PMDTA prevents any direct interaction between the fluorenide anion and magnesium, giving solvens separated ion pairs with the unusual and hitherto rare example of an organomagnesium cation [Mg2Me2(pmdt)2]2+. The 1:3 compound 5 has a more complicated structure, related to that of alkali metal alkynyl magnesates.

Synthesis and structure of new trichloromethyl-β-diketones — 5-Trichloromethylisoxazole and 5-isoxazolecarboxylic acid derivatives

2005 ◽  
Vol 83 (8) ◽  
pp. 1171-1177 ◽  
Author(s):  
Marcos A.P Martins ◽  
Sergio Brondani ◽  
Victor L Leidens ◽  
Darlene C Flores ◽  
Sidnei Moura ◽  
...  
Keyword(s):  
Hydroxylamine Hydrochloride ◽  
Enol Form ◽  
Improved Method ◽  
Keto Form ◽  
Dicarbonyl Compounds ◽  
Multinuclear Nmr ◽  
Nmr Study

An improved method for the synthesis of a new series of trichloromethyl-β-diketones including 1,1,1-trichloropentan-2,4-dione (2a), 1,1,1-trichloro-3-methylhexan-2,4-dione (2b), 4,4,4-trichloro-1-phenylbutan-1,3-dione (2c), 4,4,4-trichloro-2-methyl-1-phenylbutan-1,3-dione (2d), 2-trichloroacetylcyclohexanone (2e), 4-tert-butylcyclohexanone (2f), 4-tert-butylcycloheptanone (2g), and 4-tert-butylcyclooctanone (2h) is reported. A multinuclear NMR study showed that β-dicarbonyl compounds 2b and 2d–2h are predominantly in the keto form and 2a and 2c are in the enol form. The trichloromethyl-β-diketones react with hydroxylamine hydrochloride leading to three sets of isoxazole derivatives.Key words: acetals, acylation, trichloromethyl-1,3-diketones, 2-trichloroacetylcycloalkanones, isoxazoles, cyclocondensation.

scholarly journals Determination of the enol form of asymmetric 1,3-dicarbonyl compounds: 2D HMBC NMR data and DFT calculations

2018 ◽  
Vol 83 (9) ◽  
pp. 953-968
Author(s):  
Meltem Tan ◽  
İshak Bildirici ◽  
Nurettin Mengeş
Keyword(s):  
Experimental Data ◽  
Driving Force ◽  
Theoretical Calculations ◽  
Enol Form ◽  
Dihedral Angles ◽  
Dicarbonyl Compounds ◽  
1H And 13C Nmr ◽  
Nmr Data ◽  
Cdcl3 Solution

In this study, a series of asymmetric aryl 1,3-dicarbonyl compounds were synthesized and their enol forms were observed via experimental data and theoretical calculations. According to the 1H- and 13C-NMR results, all the investigated compounds were found as a single enol form in CDCl3 solution. Moreover, their HMBC spectra were applied to identify the observed enol forms and correlations between certain protons and carbon atoms were considered. The dihedral angles of the asymmetric compounds that have aryl units on both sides were calculated by DFT to understand the reason for the observed enol forms. Small dihedral angles caused longer conjugation, resulting in more stable compounds and it was found that the observed enol forms were based on small dihedral angles, namely, resonance is the driving force. Furthermore, the compounds possessing both aryl and alkyl moieties prefer the enol form towards the aromatic ring side due to longer conjugation.

Dicarbonyl derived post-translational modifications: chemistry bridging biology and aging-related disease

2020 ◽  
Vol 64 (1) ◽  
pp. 97-110
Author(s):  
Christian Sibbersen ◽  
Mogens Johannsen
Keyword(s):  
Mass Spectrometry ◽  
Future Research ◽  
Amino Acid Residues ◽  
Post Translational Modification ◽  
Dicarbonyl Compounds ◽  
Protein Targets ◽  
Post Translational Modifications ◽  
Reactive Protein ◽  
Glycation End Products ◽  
Direct Mass Spectrometry

Abstract In living systems, nucleophilic amino acid residues are prone to non-enzymatic post-translational modification by electrophiles. α-Dicarbonyl compounds are a special type of electrophiles that can react irreversibly with lysine, arginine, and cysteine residues via complex mechanisms to form post-translational modifications known as advanced glycation end-products (AGEs). Glyoxal, methylglyoxal, and 3-deoxyglucosone are the major endogenous dicarbonyls, with methylglyoxal being the most well-studied. There are several routes that lead to the formation of dicarbonyl compounds, most originating from glucose and glucose metabolism, such as the non-enzymatic decomposition of glycolytic intermediates and fructosyl amines. Although dicarbonyls are removed continuously mainly via the glyoxalase system, several conditions lead to an increase in dicarbonyl concentration and thereby AGE formation. AGEs have been implicated in diabetes and aging-related diseases, and for this reason the elucidation of their structure as well as protein targets is of great interest. Though the dicarbonyls and reactive protein side chains are of relatively simple nature, the structures of the adducts as well as their mechanism of formation are not that trivial. Furthermore, detection of sites of modification can be demanding and current best practices rely on either direct mass spectrometry or various methods of enrichment based on antibodies or click chemistry followed by mass spectrometry. Future research into the structure of these adducts and protein targets of dicarbonyl compounds may improve the understanding of how the mechanisms of diabetes and aging-related physiological damage occur.

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