Study of Substituted Formylchromones

Abstract

Substituted derivatives of 2-and 3-formylchromone were synthesized and studied by IR, 13 C and 1 H NMR spectroscopy and the AM1 quantum chemical method. Energy and electron distribution calculations confirm the preference of the synplanar conformation in 3-formylchromones. The calculated charges on the carbon atoms correlate well with the experimental 13 C chemical shifts. Substituents bonded to the aromatic nucleus have only small effect on the electron structure of the pyrone ring.Thanks to their biological activity, chromone derivatives are the subject of considerable pharmaceutical and chemical interest 1 . In connection with prediction and preparation of biologically active compounds we synthesized some derivatives of 2-and 3-formylchromone. Whereas the derivatives of 3-formylchromone were prepared by methods described in the literature 2 , the hitherto used method of preparation of 2-formylchromones 3 was modified to give better results.Conformational analysis was performed using the AM1 quantum chemical method, the electron structure was studied by 13 C and 1 H NMR spectroscopy and the theoretical AM1 method. EXPERIMENTALThe melting points were determined on a Kofler block and are uncorrected. IR spectra were recorded in Nujol on a Specord 75 IR instrument (Zeiss, Jena) in the region 400 -4 000 cm −1 . NMR spectra were measured on an FT NMR spectrometer Bruker AM 300 at 298 K in CDCl 3 with tetramethylsilane as internal standard. The resolution in the 1 H NMR spectra was 0.12 Hz per point. Parameters of the 13 C NMR spectra (75.46 MHz) are as follows: relaxation delay 3 s, pulse width 30°, digital resolution 1.6 Hz per point. The 13 C NMR signals were assigned using a semiselective INEPT experiment, optimized to the long-range coupling constant value J = 6 Hz. Synthesis of Nitrones Ia -If. General MethodA solution of sodium ethoxide (prepared from 44 mg (2 mmol) of Na and 15 ml of ethanol) was added dropwise to a cold (−5 to 0 °C) solution of the 2-methylchromone derivative (2 mmol) andSubstituted Formylchromones

Synthesis and Reactions of New 4-Oxo-4H-benzopyran-3-carboxaldehydes Containing Hydroxy Groups or 2-Oxopyran Cycles

“…The difference in the heats of formation is about 20 kJ mol -1 for acetophenones 1 and 22 -26 kJ mol -1 for 3-formylchromones 3, 5 . In accordance with the 1 H NMR spectra, the results of theoretical calculation of both isomers of aldehydes 5d and 5d 1 (Scheme 2) shows that the isomer 5d is about 4.5 kJ/mol more stable than the isomer 5d 1 . …”

Synthesis of some new azole, azepine, pyridine, and pyrimidine derivatives using 6‐hydroxy‐4H‐4‐oxo[1]‐benzopyran‐3‐ carboxaldehyde as a versatile starting material

“…The versatile starting compound, 6-hydroxy-4H-4-oxo[l]benzopyran-3-carboxaldehyde (1) [13] was obtained in good yield from Vilsmeier-Haack formylation of 2,5-dihydroxy acetophenone. Compound 1 was condensed with hydroxylamine hydrochloride in ethanol to give a quantitative yield of the corresponding oxime 2 that was refluxed in acetic anhydride to give 6-acetoxy-4H-4-oxo [1]-benzopyran-3-carbonitrile (3).…”

Synthesis, antifungal activity and semi-empirical AM1-MO calculations of some new 4-oxo-4H-chromene derivatives

“…These compounds possess a highly polarized C2-C3 -bond and their reactions with dinucleophiles start predominantly from the attack of the unsubstituted C-2 atom (1,4-addition) and are accompanied by pyrone ring opening to form the -dicarbonyl intermediate capable of undergoing intramolecular heterocyclizations [7,8]. In continuation to our interest in the chemistry of 4-oxo-4H-chromene-3carbaldehydes ring system [9][10][11][12][13][14], owing to its considerable biological activities. The present work describes the preparation of new systems derived from the reaction of 4-oxo-4H-chromene-3-carbaldehydes 1a,b with primary amines 2a,e and amide/thioamide derivatives 6a-d in polar and non-polar solvents.…”