Ring transformation of chromone-3-carboxamide

4-Hydroxycoumarin-3-carboxaldehyde (5) was obtained from chromone-3-carboxaldehyde (1) via chromone-3-carboxamide (2) and 3-aminomethylene-2H-chroman-2,4-dione (3). 3-Alkylaminomethylenechroman-2,4-diones (7,8) were obtained from the reaction of primary aliphatic amines with chromone-3-carboxamide (2). Treatment of chromone-3-carboxamide with sodium methoxide gives 3-(2-hydroxybenzoyl)-2H-chromeno[2,3-b]pyridine-2,5(1H)-dione (9).     

Reactions of chromone-3-carboxamides with 2-cyanothioacetamides

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Synthesis and characterization of new metal complexes of thiosemicarbazone derived from 4-phenyl-3-thiosemicarbazide and chromone-3-carboxaldehyde

Summary The reaction between chromone-3-carboxaldehyde-4-phenylthiosemicarbazone (HCPT) and some hydrated metal salts of Co^II, Ni^II and Cu^II give complexes of the type [Cu(HCPT)Cl₂],[Cu(CPT)BrH₂O],[Cu(CPT)₂]·2H₂O, [Ni(CPT)₂(H₂O)₂]·2H₂O, [Co(CPT)₂(OAc)] and [Co(CPT)₂(H₂O)₂]X·2H₂O (where X=Cl or Br). The metal complexes were characterized by elemental analyses, molar conductivities, and spectal (i.r. and visible) and magnetic studies. I.r. spectra show that the HCPT coordinates in the thione or thiol form and behaves in a bidentate manner. Also, HCPT behaves as an oxidizing agent towards Co^II forming diamagnetic Co^III complexes. An octahedral structure is proposed for both Co^III and Ni^II complexes, while a square-planar structure is proposed for Cu^II complexes on the basis of magnetic and spectral measurements.     

Reaction of chromone-3-carboxaldehydes with TOSMIC: synthesis of 4-(2-hydroxybenzoyl)pyrroles

Chromone-3-carboxaldehydes 1 react with tosylmethylisocyanide (TOSMIC) in the presence of DBU in THF at room temperature to furnish, after in situ deformylation, good yields of 2-tosyl-4-(2-hydroxybenzoyl)pyrroles 2. When the same reaction is performed with potassium carbonate in methanol under reflux pyrroles 2 are again isolated, but in lower yields. Finally, from the reaction of 1a in the presence of a stronger base (NaOH) only a small amount of the 3-substituted derivative 3a along with polymeric material is isolated.     

Kinetics and mechanism of hydrogen peroxide oxidation of chromone-3-carboxaldehydes in aqueous acid and micellar media

Oxidation of chromone-3-carboxaldehyde (CCA) and substituted analogues by H₂O₂ has been carried out in aqueous acid (HCl and H₂SO₄) and micellar media. Reaction kinetics indicated order in [CCA] as well as [H₂O₂] to be unity while it is a fraction (1 > n > O) in [acid]. Reaction rates were found to be faster in the solvents of low-dielectric constant (D). Added salt (KCl or (NH₄)₂SO₄) increased the rate of oxidation marginally. On the basis of observed linearity of Amis plot and marginal positive salt effect, protonated CCA (enol form of CCA, a cation) and H₂O₂ (neutral molecule) were considered as reactive species in the rate limiting step. Reaction rates were found to be enhanced significantly in anionic and nonionic micellar (sodium dodecylsulfate (SDS) and Triton X-100 (Tx), respectively) media. However, cationic micelles [cetyl trimethyl ammonium bromide (CTAB)] indicated marginal retardation effect. Effect of anionic and cationic micelles has been interpreted in terms of electrostatic interactions, while that of nonionic micelles in terms of hydrophobic interactions. Structure-reactivity correlations have been interpreted by Hammett's equation. Negative “ρ” (reaction constant) values indicated cationic transition state. © 1996 John Wiley & Sons, Inc.     

The reaction of ethyl chromone-2-carboxylates with 1,2-diaminobenzene

Ethyl chromone-2-carboxylate and all its benzoanalogs were prepared and caused to react with 1,2-diami-nobenzene to give 2-(2-hydroxybenzoyl)methinyl-3-oxo-1,2,3,4-tetrahydroquinoxaline and its benzo analogs. The condensation products of diethyl oxalate and methyl hydroxyaryl ketones which were required for the preparation of the starting esters, were found to be subject to ring chain tautomerism.     

Synthesis of dispiropyrrolidines from chromone-3-carbaldehyde using sarcosine and ninhydrin as the source of an azomethine ylide

An efficient one-pot synthesis of several novel dispirochromanopyrrolidines has been accomplished by the reaction of chromone-3-carbaldehyde, sarcosine and ninhydrin. The structures were confirmed by single crystal X-ray diffraction studies.     

Reaction of chromone-3-carbaldehyde with α-amino acids—syntheses of 3- and 4-(2-hydroxybenzoyl)pyrroles

Azomethine ylides generated from the reaction of chromone-3-carbaldehyde with α-amino acids undergo 1,5-electrocyclization reactions to afford 3- and 4-(2-hydroxybenzoyl)pyrroles. These ylides can be trapped with dipolarophiles in 1,3-dipolar cycloaddition reactions to yield chromonyl pyrrolidines. The reaction of chromone-3-carbaldehyde with methyl glycinate gives a mixture of pyrrole, pyridine, and 3-aza-9-xanthenone derivatives.     

A study of the reactions of 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones with chromone-3-carboxaldehydes

Reaction of 3-formylchromones with 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones in the presence of pyridine leads to formation of a mixture of novel N-thioaroyl-5-hydroxy-2H,5H-pyrano[3,2-с]chromen-2-one-3-carboxamides and 2-aryl-5-(4′-oxochromen-3′-yl)-6,7-dihydro-4H,5H-pyrano[2,3-d][1,3]thiazine-4,7-diones. The yields of these compounds clearly depend on the nature of the substituent on the 3-formylchromone and on the reaction conditions.     

Synthesis, structure, infrared and fluorescence spectra of new rare earth complexes with 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand and its four complexes, [LnL2(NO3)2]NO3 [Ln = Eu(1), Sm(2), Tb(3), Dy(4)], were synthesized. The complexes were characterized by the elemental analyses, molar conductivity and IR spectra. The crystal and molecular structure of Sm(III) complex was determined by single-crystal X-ray diffraction: crystallized in the triclinic system, space group P-1, Z = 1, a = 11.037(4) A, b = 14.770(5) A, c = 15.032(7) A, alpha = 60.583(4), beta = 75.528(7), gamma = 88.999(4), R1 = 0.0349. The fluorescence properties of complexes in the solid state and in the organic solvent were studied in detail, respectively. Under the excitation of ultraviolet light, strong red fluorescence of solid europium complex was observed. But the green fluorescence of solid terbium complex was not observed. These observations show that the ligand favor energy transfers to the emitting energy level of Eu3+. Some factors that influence the fluorescent intensity were also discussed.     

Synthesis, characterization, cytotoxic activity and DNA binding Ni(II) complex with the 6-hydroxy chromone-3-carbaldehyde thiosemicarbazone

A new ligand L, 6-hydroxy chromone-3-carbaldehyde thiosemicarbazone, and its Ni(II) complex have been synthesized and characterized. The crystal structure of Ni(II) complex was determined by single crystal X-ray diffraction. Ni(II) complex and ligand L were subjected to biological tests in vitro using THP-1, Raji and Hela cancer cell lines. Compared with the ligand, Ni(II) complex showed significant cytotoxic activity against these three cancer cell lines. The interactions of Ni(II) complex and ligand L with calf thymus DNA were then investigated by spectrometric titration, ethidium bromide displacement experiments and viscosity measurements methods. The experimental results indicated that Ni(II) complex bound to DNA by intercalative mode via the ligand L. The intrinsic binding constants of Ni(II) complex and ligand L with DNA were (1.10 ± 0.65) × 10⁶ M⁻¹ and (1.48 ± 0.57) × 10⁵ M⁻¹, respectively.     

New metal complexes derived from S-benzyldithiocarbazate (SBDTC) and chromone-3-carboxaldehyde: synthesis,characterization, antimicrobial,antitumor activity and DFT calculations

Novel monobasic tridentate ONS donor ligand (HL) was synthesized from the condensation reaction of chromone-3-carboxaldehyde with S-benzyldithiocarbazate (SBDTC). Reaction of the ligand with the metal ions copper(II), nickel(II), cobalt(II), oxidovanadium(IV), cerium(III), manganese(II), zinc(II), and cadmium(II) afforded dimeric complexes with the general formula [ML(Y)_m(H₂O)_x]₂·(Y)_m·nH₂O·zCH₃OH, Y?=?NO₃ or Cl, m?=?0–2, x?=?0–2, n?=?0–2, and z?=?0–1 for all complexes except oxidovanadium(IV) complex which has the formula [VOL(H₂O)]₂(SO₄). Structures of the ligand and its metal complexes were established through elemental, spectroscopic data (FT-IR, UV-Vis, and mass), thermal analyses, as well as conductivity and magnetic susceptibility measurements. The geometrical structures of the metal complexes are octahedral and square planar. The ligand and its complexes were subjected to in vitro bioassays against the gram-negative and gram-positive bacteria and the fungus strain with good results for some of these compounds. The antitumor activity of the ligand and its copper(II) and oxidovanadium(IV) complexes were investigated against HepG2 cell line. The molecular parameters of the ligand and its metal complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program, and computed data were correlated with the experimental results. The HOMO→LUMO electron transition potentially occurs from S-benzyldithiocarbazate to chromone moieties with 4.048?eV. The Mn(II) complex has the highest value of energy barrier, while Cu(II) complex has the lowest value among the complexes. All synthesized complexes have energy gap lower than free ligand and therefore these complexes are more reactive than the free ligand.     

The standard molar enthalpies of formation of chromone-3-carboxylic acid, 6-methylchromone-2-carboxylic acid,and 6-methyl-4-chromanone determined by micro-combustion calorimetry

The energies of combustion of chromone-3-carboxylic acid (C3CA), 6-methylchromone-2-carboxylic acid (6MCC), and 6-methyl-4-chromanone (6M4C) were determined using an isoperibolic micro-combustion calorimeter. The calorimeter used in the present work has been assembled, calibrated, and tested in our laboratory with the desired results. Prior to the measurement of the energies of combustion, the purities, heat capacities (C _p), fusion temperatures (T _fus), and enthalpies of melting (Δ_fus H) for each compound were determined by differential scanning calorimetry. The values of the energies of combustion were used to derive standard molar enthalpies of combustion ( \( \Delta _{{\text{c}}} H_{{\text{m}}}^{\circ } \) ) and standard molar enthalpies of formation ( \( \Delta _{{\text{f}}} H_{{\text{m}}}^{\circ } \) ) in the crystalline phase at T = 298.15 K. The values found for the \( \Delta _{{\text{f}}} H_{{\text{m}}}^{\circ } \) of C3CA, 6MCC, and 6M4C were ?(619.5 ± 2.6), ?(656.2 ± 2.2), and ?(308.9 ± 3.0) kJ mol^?1, respectively.     

A novel conversion of chromone-3-carboxaldehyde to 5-nitro-2,3-benzofurandione-(Z)-2-oxime

The conversion of chromone-3-carboxaldehyde to 5-nitro-2,3-benzofurandione-($\text{Z}$)-2-oxime under nitrating conditions is reported.     

Serendipitous stereoselective synthesis of brand-new fluorescent dyes: (1Z)-3-(alkylimino)-1-[(chromone-3-yl)methylene]-1,3-dihydro-9H-furo[3,4-b]chromen-9-one-type fluorophores with blue fluorescence emission properties

The reactions of 3-formylchromones with alkyl isocyanides in dry dichloromethane at room temperature lead to new types of organic fluorophores (1Z)-3-(alkylimino)-1-[(chromone-3-yl)methylene]-1,3-dihydro-9H-furo[3,4-b]chromen-9-one, which exhibited strong blue emission in solution. The reactions involve a [4+1] cycloaddition followed by an activated electrophilic aromatic substitution at the furan ring and dehydration sequence.     

Réaction de l'acide chromone-2 carboxylique avec les carbodiimides: Synthèse de spiro [(chromanone-4)-2: 5′-hydantoïnes]

The reaction of 4-oxo-1-benzopyran-2-carboxylic acid ( I ) with carbodi-imides 2 yield N-acylureas 3 . These N-acylureas are easly cyclised in ethanol to yield the corresponding spiro-4-oxo-1-benzopyrans 4 .