Pyrone Ring Research Articles

Transformations of 3-acyl-4H-polyfluorochromen-4-ones under the action of amino acids and biogenic amines

For the first time 6,7,8-trifluoro- and 5,6,7,8-tetrafluorinated 3-benzoylflavones have been obtained. Their reactions with amino acids and biogenic amines were studied in comparison with polyfluorinated 3-acetyl-2-methylchromones. For chromones, reactions at the C-2 are preferred, which lead to the pyrone ring opening to form N-substituted aminoenketones. Whereas in the case of flavones the main route is the nucleophilic aromatic substitution of the fluorine atom at the C-7. Flavones and chromones react in the same way both with dopamine to give aminoenketones, and with proline to form 7-amino-substituted chromen-4-ones. All the reactions of chromen-4-ones are accompanied by deacylation, except ones of flavones with proline. Among the synthesized aminoenketones, compounds with high antimycotic and antibacterial action were found.

Phototoxicity of 7-oxycoumarins with keratinocytes in culture

Seventy-one 7-oxycoumarins, 66 synthesized and 5 commercially sourced, were tested for their ability to inhibit growth in murine PAM212 keratinocytes. Forty-nine compounds from the library demonstrated light-induced lethality. None was toxic in the absence of UVA light. Structure-activity correlations indicate that the ability of the compounds to inhibit cell growth was dependent not only on their physiochemical characteristics, but also on their ability to absorb UVA light. Relative lipophilicity was an important factor as was electron density in the pyrone ring. Coumarins with electron withdrawing moieties – cyano and fluoro at C3 – were considerably less active while those with bromines or iodine at that location displayed enhanced activity. Coumarins that were found to inhibit keratinocyte growth were also tested for photo-induced DNA plasmid nicking. A concentration-dependent alteration in migration on neutral gels caused by nicking was observed.

Microwave Assisted Rapid Extraction and Characterization of Coumarin from Fig Plant (Ficus carica)

Coumarins are fragrant natural bioactive organic compound find application as aroma, flavor and wide medicinal use. Fig plant (Ficus Carica) is a very good source of Coumarins. Coumarins are a member of the benzopyrone family and it has a benzene ring joined to a pyrone ring. There is a need for effective extraction and purification of Coumarins from plant materials. Different methods of extraction of Courmarin from Ficus Carica has been studied in this paper, among them, microwave extraction (180 W power) provided rapid extraction with 10 minutes time with extract yield of 0.67 g as compared to that of 1 hour of water bath extraction at 60C. Coumarin was isolated from the crude extract using NaOH and petroleum ether and their presence was characterized confirmed using UV spectroscopy, IR spectroscopy, TLC and fluorescence test. The antibacterial activity of coumarin was also evaluated using disc diffusion method and Minimum Inhibition Count (MIC). The present study analyzes and provides method of microwave assisted rapid extraction of Coumarin from Fig plant (Ficus Carica) and its characterization, which could be widely used as generic method from natural materials for different applications.

Exploring the transfer of hydrogen atom from kaempferol-based compounds to hydroxyl radical at ground state using PCM-DFT approach

Thermodynamic and kinetic studies of the hydrogen atom transfer (HAT) from hydroxyl (OH) groups of four kaempferol-based compounds, namely kaempferol, morin, morin-5*-sulfonate and morin-7-O-sulfate to hydroxyl radical (·OH), have been carried out using density functional theory (DFT) methods at the CAM-B3LYP/6–311++G(d,p) level equipped with polarizable continuum model (PCM) of solvation. All HAT reactions in aqueous solution are exothermic and spontaneous. For most compounds, the most preferable OH group for HAT is situated at position C3 (O3-H3) on the pyrone ring. The reaction potential of such a reactive group is found to be highest in morin-7-O-sulfate. The rate constants for the HAT reactions at different OH groups of each compound have been determined based on the transition state theory. The presence of substituents leads to the variation in either the characteristic interactions at the reactive site or the charge distribution on transition-state geometries, hence significantly affecting the kinetics of HAT. The highest rate of HAT is resulted for the OH group at position C4* (O4*-H4*) on the phenyl ring (ring B) of morin-5*-sulfonate because a hydrogen bond between ·OH and the sulfonate group favors the formation of transition state. However, for most compounds under study, the HAT reaction at O3-H3 initiated by ·OH is highly favorable both thermodynamically and kinetically.

A Copper(II) tris-imidazolylphosphine complex as a functional model of flavonol 2,4-dioxygenase

Reaction of tetrakis(acetonitrile)copper(I) perchlorate ([Cu(NCCH3)4][ClO4]), tris-1-ethyl-4-methylimidazolylphosphine (T1Et4MeIP) (1) and 3-hydroxyflavone (flavH) under ambient conditions produces an in-situ generated flavonol bound copper(II) complex, which converts to a stable green complex that formulates to [Cu(T1Et4MeIP)(flav)][ClO4] (2). The crystal structure of 2 was determined by X-ray diffraction and crystallizes in a triclinic system (P1¯) with unit cell dimensions of a = 14.537(15) Å, b = 15.794(14) Å, c = 17.044(17) Å, α = 65.58(3)˚, β = 86.80(5)˚, γ = 73.34(4)˚, V = 3376(6) Å3 and Z = 2. While the five-coordinate copper(II) complex is stable under ambient conditions in the solid state, it undergoes oxidative scission of the flavonol pyrone ring under photolytic (300 nm) and/or thermal (120 °C) conditions in the presence of molecular oxygen. The degradative process produces the corresponding methylated products: methylbenzoate, methyl salicylate and N,N-dimethylbenzamide. In addition, the previously undisclosed single crystal X-ray structure of tris-1-ethyl-4-methylimidazolylphosphine (1), T1Et4MeIP, is also reported.

Excited state hydrogen atom transfer in micro-solvated dicoumarol: A TDDFT/EFP1 study.

Ground (S0) and excited (S1) state properties of dicoumarol (DC) are investigated by applying density functional theory (DFT) and time dependent DFT (TDDFT) interfacing with the effective fragment potential (EFP) method of solvation. Benzene and pyrone rings of the each 4-hydroxy coumarin (4HC) moiety are in a plane and these planes are twisted by 180° with respect to each other. Two intra-molecular hydrogen bonds (HB) CO⋯HO exist between the carbonyl (CO) and hydroxyl (OH) groups of different 4HC moieties (4HC-1 and 4HC-2). DC(H2O)3 complex is formed using the original EFP model (EFP1). Four inter-molecular HBs are established by the carbonyl and hydroxyl oxygen atoms of 4HC-1 and 4HC-2 moieties; two HBs with two solvent molecules on one side of the complex and other two HBs with one solvent molecule at the other side. In S1 state, the hydrogen atomtransfer takes place only from the hydroxyl group of 4HC-1 to the carbonyl group of 4HC-2. The natural charge analysis and the modification of HBs manifest the intra-molecular charge transfer (ICT) from one 4HC moiety to another. Theoretical and experimental studies of the absorption spectra, and the theoretical study of potential energy curves of OH bonds at both S0 and S1 states affirm the hydrogen atom transfer from the hydroxyl group of 4HC-1 to the carbonyl group of 4HC-2 moiety.

A novel entry to xanthones by an intramolecular Diels-Alder reaction involving 2-(1,2-dichlorovinyloxy) aryl dienones

A wide array of synthetic methods are described in the literature for the preparation of xanthones—a prominent class of tricyclic molecules that occur widely in nature. Majority of these reported methods involve linking the two aromatic rings and forming the central pyrone ring using a variety of classical and non-classical cyclization strategies. In a conceptually different approach, we describe here a new xanthone synthesis wherein both the pyrone and the second aromatic rings were forged in a single step by an intramolecular cycloaddition reaction involving 2-(1,2-dichlorovinyloxy) aryldienones.

Khellinoflavanone, a Semisynthetic Derivative of Khellin, Overcomes Benzo[a]pyrene Toxicity in Human Normal and Cancer Cells That Express CYP1A1.

Cytochrome P450 family 1 (CYP1) enzymes catalyze the metabolic activation of environmental procarcinogens such as benzo[a]pyrene, B[a]P, into carcinogens, which initiates the process of carcinogenesis. Thus, stopping the metabolic activation of procarcinogens can possibly prevent the onset of cancer. Several natural products have been reported to show unique ability in inhibiting CYP1 enzymes. We found that khellin, a naturally occurring furanochromone from Ammi visnaga, inhibits CYP1A1 enzyme with an IC50 value of 4.02 μM in CYP1A1-overexpressing human HEK293 suspension cells. To further explore this natural product for discovery of more potent and selective CYP1A1 inhibitors, two sets of semisynthetic derivatives were prepared. Treatment of khellin with alkali results in opening of a pyrone ring, yielding khellinone (2). Claisen–Schmidt condensation of khellinone (2) with various aldehydes in presence of potassium hydroxide, at room temperature, provides a series of furanochalcones 3a–v (khellinochalcones). Treatment of khellinone (2) with aryl aldehydes in the presence of piperidine, under reflux, affords the flavanone series of compounds 4a–p (khellinoflavanones). The khellinoflavanone 4l potently inhibited CYP1A1 with an IC50 value of 140 nM in live cells, with 170-fold selectivity over CYP1B1 (IC50 for CYP1B1 = 23.8 μM). Compound 4l at 3× IC50 concentration for inhibition of CYP1A1 completely protected HEK293 cells from CYP1A1-mediated B[a]P toxicity. Lung cancer cells, A549 (p53+) and Calu-1 (p53-null), blocked in growth at the S-phase by B[a]P were restored into the cell cycle by compound 4l. The results presented herein strongly indicate the potential of these khellin derivatives for further development as cancer chemopreventive agents.

A Systematic Review on Pharmacological Activities of 4-Methylumbelliferon

Umbelliferon, the natural crenelated coumarin distributed in the plants of a piaceae family, has shown various biological activities, especially as a cancer chemo preventive agent. Coumarins have been categorized as a member of family of benzo-pyrone, that consist of pyrone ring united to benzene ring. The benzo-pyrones may be sectioned to alfa type that coumarins belong and the gama type that flavonoids have been major members. Coumarins are chemical entity which has being synthesized in the past few years many forms of its derivatives; the entity provides the principal origin of motivating to numerous chemist to investigate its diverse medical efforts especially with regards to the anticoagulant activity. In present article we review recent 4-Methylumbelliferon, (4-MU) that are synthesized with it pharmacological activities antioxidant, anti-inflammatory, antimicrobial activity, ant hepatitis, hepatoprotective, anticancer, antipyretic and analgesic activity. How to Cite this Article Pubmed Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. SRP. 2018; 9(1): 49-54. doi:10.5530/srp.2018.1.10 Web Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. http://www.sysrevpharm.org/?mno=302644548 [Access: March 28, 2021]. doi:10.5530/srp.2018.1.10 AMA (American Medical Association) Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. SRP. 2018; 9(1): 49-54. doi:10.5530/srp.2018.1.10 Vancouver/ICMJE Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. SRP. (2018), [cited March 28, 2021]; 9(1): 49-54. doi:10.5530/srp.2018.1.10 Harvard Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad (2018) Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. SRP, 9 (1), 49-54. doi:10.5530/srp.2018.1.10 Turabian Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. 2018. Systematic Review on Pharmacological Activities of Reviews in Pharmacy, 9 (1), 49-54. doi:10.5530/srp.2018.1.10 Chicago Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. A Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. Systematic Reviews in Pharmacy 9 (2018), 49-54. doi:10.5530/srp.2018.1.10 MLA (The Modern Language Association) Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad. A Systematic Review on Pharmacological Activities of 4-Methylumbelliferon. Systematic Reviews in Pharmacy 9.1 (2018), 49-54. Print. doi:10.5530/srp.2018.1.10 APA (American Psychological Association) Style Yasmeen Al-Majedy, Abdul Amir Kadhum, Hiba Ibraheem, Ahmed Al-Amiery, Ahmed Abdel Moneim, Abu Bakar Mohamad (2018) Systematic Review on Pharmacological Activities of Reviews in Pharmacy, 9 (1), 49-54. doi:10.5530/srp.2018.1.10

2-Oxo-2H-chromen-7-yl 4-methylbenzoate

In the title compound, C17H12O4, the benzoate ring is oriented at an acute angle of 60.14 (13)° relative to the coumarin plane (r.m.s. deviation = 0.006 Å). This conformation is stabilized by an intramolecular C—H...O weak hydrogen bond, which forms a five-membered ring. Also present are π–π stacking interactions between neighbouring pyrone and benzene rings [centroid-to-centroid distances in the range 3.6286 (1)–3.6459 (1) Å] and C=O...π interactions [O...centroid distances in the range 3.2938 (1)–3.6132 (1) Å]. Hirshfeld surface analysis has been used to confirm and quantify the supramolecular interactions.

Modification of Polyfluoro-Containing 3-(Ethoxycarbonyl)flavones by Biogenic Amines and Amino Acids

Aim and Objective: The objective of our work was to study the peculiarities of transformations of fluorine-containing flavone-3-carboxylates with N-nucleophiles, including biogenic amines and amino acids. Materials and Methods: 6,7,8-Trifluoro and 5,6,7,8-tetrafluoroflavone-3-carboxylates were involved in interactions with a number of N-nucleophiles, such as pyrrolidine, morpholine, proline, arginine, gammaaminobutyric acid, beta-alanine, histamine, dopamine and amantadine under different reaction conditions. All synthesized compounds were characterized by NMR 1H, 19F, (NMR 13C for some compounds) and IR spectroscopic data, and elemental analysis. Results: 3-(Ethoxycarbonyl)polyfluoroflavones react with morpholine, pyrrolidine and L-proline to form 7- monosubstituted flavone-3-carboxylates. For the reactions of tetrafluoroflavone with pyrrolidine and morpholine, the formation of 5,7-disubstituted products is also possible. Interaction with gamma-aminobutyric acid leads to the 4-{[3-ethoxy-2-(2-hydroxypolyfluorobenzoyl)-3-oxo-1-phenylprop-1-enyl]amino}butanoic acids as a result of the pyrone ring opening. In reactions with dopamine, histamine, L-arginine and β-alanine, polyfluoroflavone-3-carboxylates underwent a chromone-coumarin rearrangement. 3-(Ethoxycarbonyl)tetrafluoroflavone forms with amantadine the nucleophilic aromatic substitution product, while trifluoro-substituted analog gives the chromone-coumarin rearrangement product. Conclusion: This work showed possibilities of chemical modification of polyfluorinated flavones in the reactions with amines depending on the structure of the nucleophilic reagent. Synthesized compounds are of interest for biological testing.

Pharmacological and Nutritional Effects of Natural Coumarins and Their Structure-Activity Relationships.

Coumarins are fused benzene and pyrone ring systems with a wide spectrum of bioactivities, including antitumor, anti-inflammation, antiviral, and antibacterial effects. In this paper, the current development of coumarin-based drugs is introduced, and their structure-activity relationship is discussed by reviewing the relevant literature published in the past 20 years. Coumarin molecules can be customized by the target site to prevent systemic side effects by virtue of structural modification. The ortho-phenolic hydroxyl on the benzene ring has remarkable antioxidant and antitumor activities. Coumarins with aryl groups at the C-4 position have good activities in anti-HIV, antitumor, anti-inflammation, and analgesia. C-3 phenylcoumarins have strong anti-HIV and antioxidant effects. Tetracycline pyranocoumarins can significantly inhibit HIV; osthol structural analogues have antimicrobial activity. Praeruptorin C and its derivatives play an important role in lowering blood pressure and dilating coronary arteries, and khellactone derivatives have significant inhibitory effects on AIDS, cancer, and cardiovascular diseases. It is concluded that the specific site on the core structure of coumarin exhibits one or more activities due to the electronic or steric effects of the substituents. This review is intended to be conducive to rational design and development of more active and less toxic agents with a coumarin scaffold.

2-Oxo-2H-chromen-7-yl 4-tert-butyl-benzoate.

In the title compound, C20H18O4, the benzoate ring is oriented at an acute angle of 33.10 (12)° with respect to the planar (r.m.s deviation = 0.016 Å) coumarin ring system. An intra-molecular C-H⋯O hydrogen bond closes an S(6) ring motif. In the crystal, C-H⋯O contacts generate infinite C(6) chains along the b-axis direction. Also present are π-π stacking inter-actions between neighbouring pyrone and benzene rings [centroid-centroid distance = 3.7034 (18) Å] and C=O⋯π inter-actions [O⋯centroid = 3.760 (3) Å]. The data obtained from quantum chemical calculations performed on the title compound are in good agreement with the observed structure, although the calculated C-O-C-C torsion angle between the coumarin ring system and the benzoate ring (129.1°) is somewhat lower than the observed value [141.3 (3)°]. Hirshfeld surface analysis has been used to confirm and qu-antify the supra-molecular inter-actions.

Mechanistic Investigations of Photoinduced Oxygenation of Ru(II) Bis-bipyridyl Flavonolate Complexes.

We previously reported that a Ru-bound flavonolate model of flavonol dioxygenases, [RuII(bpy)2(3-hydroxyfla)][PF6], photochemically reacts with dioxygen in two different manners. Broad-band excitation generates mixtures of products characteristic of 1,3-addition of dioxygen across the central pyrone ring, as is observed in enzymatic reactions. However, low temperature excitation at wavelengths longer than 400 nm generates a unique Ru-bound 2-benzoatophenylglyoxylate product resulting from a 1,2-dioxetane intermediate. Herein, we investigate this reactivity in a series of Ru(II)bis-bipyridyl flavonolate complexes [RuII(bpy)2(3-hydroxyflaR)][PF6] (bpy = 2,2'-bipyridine; fla = flavonolate; R = p-OMe (1), p-Me (2), p-H (3), p-Cl (4)), and [RuII(bpy)2(5-hydroxyfla)][PF6] (5). The complexes' structures, photophysical and electrochemical properties, and photochemical reactivity with oxygen were investigated in detail. Two different reaction product mixtures, from 1,2- and 1,3-additions of dioxygen, are observed by illumination into distinct excitation/emission manifolds. By analogy to previous reports of excited state intramolecular proton transfer, the two manifolds are attributed to tautomeric diradicals that predict the observed reactivity patterns.

Identification of the Biosynthetic Gene Cluster for Himeic Acid A: A Ubiquitin-Activating Enzyme (E1) Inhibitor in Aspergillus japonicus MF275.

Himeic acid A, which is produced by the marine fungus Aspergillus japonicus MF275, is a specific inhibitor of the ubiquitin-activating enzyme E1 in the ubiquitin-proteasome system. To elucidate the mechanism of himeic acid biosynthesis, feeding experiments with labeled precursors have been performed. The long fatty acyl side chain attached to the pyrone ring is of polyketide origin, whereas the amide substituent is derived from leucine. These results suggest that a polyketide synthase-nonribosomal peptide synthase (PKS-NRPS) is involved in himeic acid biosynthesis. A candidate gene cluster was selected from the results of genome sequencing analysis. Disruption of the PKS-NRPS gene by Agrobacterium-mediated transformation confirms that HimA PKS-NRPS is involved in himeic acid biosynthesis. Thus, the him biosynthetic gene cluster for himeic acid in A. japonicus MF275 has been identified.

An investigation on 3-acetyl-7-methoxy-coumarin Schiff bases and their Ru(ii) metallates with potent antiproliferative activity and enhanced LDH and NO release.

New cyclometallated ruthenium(ii) complexes of 3-acetyl-7-methoxycoumarin-4N-substituted thiosemicarbazones were synthesized and characterized by analytical and spectral techniques. The crystal structures of the ligands H2L1–3 and complexes (1, 2 and 4) were confirmed by X-ray crystallography. The analysis showed that the ligands have undergone C–H activation at the C(4) carbon of the pyrone ring and acted in a tridentate fashion by binding through C, N and S atoms. CT-DNA and protein (BSA/HSA) binding studies were carried out to analyze their interaction with biomolecules. Good binding affinity with DNA was observed with intercalative binding mode, which was further confirmed by EB displacement and viscosity measurement studies. The quenching mechanism with BSA/HSA was found to be static. Three dimensional (3D) fluorescence measurements were carried out to validate the micro environmental changes in the serum albumins. Their antioxidant propensity and antimicrobial study insisted that the compounds displayed good spectrum of activity. Evaluation of their anticancer potential against MCF-7 (human breast cancer) and A549 (human lung carcinoma) cell lines revealed that the complexes exhibited better activity than the ligands and cisplatin. Further, the results of LDH and NO release assays supported the cytotoxic nature of the compounds. The non-toxic nature of the compounds was established by testing against the non-cancerous cell line HaCaT (human normal keratinocyte).

Trimerisation of carbon suboxide at a di-titanium centre to form a pyrone ring system.

The reaction of the syn-bimetallic bis(pentalene)dititanium complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(1,4-SiiPr3)2) 1 with carbon suboxide (O[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]O, C3O2) results in trimerisation of the latter and formation of the structurally characterised complex [{Ti2(μ:η5,η5-Pn†)2}{μ-C9O6}]. The trimeric bridging C9O6 unit in the latter contains a 4-pyrone core, a key feature of both the hexamer and octamer of carbon suboxide which are formed in the body from trace amounts of C3O2 and are, for example, potent inhibitors of Na+/K+-ATP-ase. The mechanism of this reaction has been studied in detail by DFT computational studies, which also suggest that the reaction proceeds via the initial formation of a mono-adduct of 1 with C3O2. Indeed, the carefully controlled reaction of 1 with C3O2 affords [Ti2(μ:η5,η5-Pn†)2 (η2-C3O2)], as the first structurally authenticated complex of carbon suboxide.

An alternative approach to the synthesis of 5H-chromeno[4,3-b]pyridin-5-one system using the cleavage of 5H,9H-pyrano[2',3':5,6]chromeno[4,3-b]pyridine-5,9-diones with binucleophiles

Hantzsch reaction has been successfully employed for a one-step assembling of pyranopyridine fragment to produce 5??,9??-pyrano[2',3':5,6]- chromeno[4,3-b]pyridine-5,9-diones which upon treatment with binucleophiles undergo chemoselective ??-pyrone ring opening with the concomitant recyclization to give five-membered cycles, providing a concise route to 6-pyrazolyl(isoxazolyl)-5H-chromeno[4,3-b]- pyridin-5-ones.

Novel copper(II), cobalt(II) and nickel(II) complexes with 5-(4-oxo-4H-chromen-3-yl)-4,5-dihydro-1,3,4-thiadiazole-2-carboxamide: Synthesis, structure, spectroscopic studies

A series of novel organic ligands, 5-(4-oxo-4H-chromen-3-yl)-4,5-dihydro-1,3,4-thiadiazole-2-carboxamide, which are the tautomeric forms of 2-oxo-2-(arylamino)-(2E)-2- [(4-hydroxy-2-oxo-2H-1-benzopyran-3-yl)-methyledene]ethanethioic acid hydrazides, have been synthesized from 3-formylchromone and oxamic acid thiohydrazides. Copper(II), cobalt(II) and nickel(II) complexes with 2-oxo-2-(arylamino)-(2E)-2-[(4-hydroxy-2-oxo-2H-1-benzopyran-3-yl)methyledene]ethanethioic acid hydrazides have been synthesized by the interaction of corresponding organic ligands with MCl2 (M = Cu, Co, Ni). The crystal structure of a copper(II) complex with 5-(4-oxo-4H-chromen-3-yl)-N-phenyl-4,5-dihydro-1,3,4-thiadiazole-2-carboxamide has been solved by a single-crystal X-ray diffraction method. The copper(II) ions in complex molecule are coordinated by aldimine nitrogen atom, thiolate sulfur atom and the oxygen atom the pyrone ring keto-group as well as two bridged chloride anions in a distorted triangular bipyramidal geometry. The electrochemical investigations of synthesized ligands and complexes have been performed by cyclic voltammetry technique.

Gold Catalysis for Heterocyclic Chemistry: A Representative Case Study on Pyrone Natural Products.

2-Pyrones and 4-pyrones are common structural motifs in bioactive natural products. However, traditional methods for their synthesis, which try to emulate the biosynthetic pathway of cyclization of a 1,3,5-tricarbonyl precursor, are often harsh and, therefore, not particularly suitable for applications to polyfunctionalized and/or sensitive target compounds. π-Acid catalysis, in contrast, has proved to be better for a systematic exploration of the pyrone estate. To this end, alkynes are used as stable ketone surrogates, which can be activated under exceedingly mild conditions due to the pronounced carbophilicity of [LAu]+ fragments (L=two electron donor ligand); attack of a tethered ester carbonyl group onto the transient alkyne-gold complex then forges the pyrone ring in a fully regiocontrolled manner.