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The first stereoselective total synthesis of cytotoxic diacetylene pyranone B is described. The key steps involved in the synthesis are base-induced elimination protocol to generate the chiral acetylenic alcohol and selective cross-coupling of unsymmetrical terminal acetylenes. [ABSTRACT FROM AUTHOR]

A simple green method has been developed for the synthesis of a series of new 3-phenyl-6-(substituted)-thiopyrano[2,3-d]thiazole-2,5,7(6H)-triones, 6-cyano-2-oxo-3-phenyl-thiopyrano[2,3-d]thiazoles, 3-phenyl-3,5,5a,11b-tetrahydro-2H,6H-chromeno-[4′,3′:4,5]thiopyrano[2,3-d]thiazole-2,6-dione and 5-amino-6-cyano-2-oxo-3-phenyl-3,7-dihydro-2H-thiopyrano[2,3-d]thiazoles via hetero-Diels-Alder reaction by conventional method and green method using lemon juice as natural acid. The structure of all the newly synthesized compounds was interpreted by elemental analyses and spectral data. The synthesized compounds were evaluated for their in vitro antibacterial activity against some pathogenic bacteria. This study is a platform for the future design of more potent antimicrobial agents. [ABSTRACT FROM AUTHOR]

The structural and optical properties of 2-Amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl) - 5, 6- dihydro - 4H-pyrano [3,2-c] quinoline-3- carbonitrile (Ph-HPQ) and 2-Amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3,2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films are studied. The compounds are polycrystalline in as- synthesised powder form; they became nanocrystallites dispersed in amorphous matrix upon thermal deposition to form thin films. FTIR spectral measurements showed no change in chemical bonds of the compounds after being deposited to form thin films. The optical properties have been determined based on spectrophotometer measurements of transmittance and reflectance at nearly normal incidence of light in the spectral range of 200–2500 nm. The absorption parameters, molar extinction coefficient, oscillator strength and electric dipole strength, are reported. The type of electron transition is determined from analysis of absorption coefficient spectra near the onset and optical absorption edges. The onset and optical energy gaps for Ph-HPQ and Ch-HPQ thin films are determined. The single oscillator model is applied to calculate the dispersion parameters of the investigated thin films. In addition, oscillator and dispersion energies, the high-frequency dielectric constant, lattice dielectric constant and ratio of free charge carriers concentrations to their effective masses are evaluated for the compounds under investigation. [ABSTRACT FROM AUTHOR]

An atom-economic route to densely functionalized thiophenes has been developed via base-catalyzed rearrangement of 5-propargyl-2H-thiopyran-4(3H)-ones involving tandem retro-thio Michael addition, propargyl isomerization, and intramolecular thio-addition to allenes. [ABSTRACT FROM PUBLISHER]

The Achmatowicz rearrangement converts furfuryl alcohols, obtainable from renewable carbohydrates, into 6-hydroxy-2H-pyrane-3(6H)-ones, which are versatile intermediates for organic synthesis. We describe here the first examples of a solvent-free mechanochemical Achmatowicz rearrangement. Furfuryl alcohols were prepared from furfurals using mechanochemically initiated reductions and Reformatsky reactions. Mechanochemical reaction conditions for the Achmatowicz rearrangement of the obtained furfuryl alcohols were optimized and applied to a series of derivatives, yielding the corresponding rearrangement products in yields of 39 to 95%. [ABSTRACT FROM AUTHOR]

This review highlights the methods used for the synthesis of enaminonitriles of pyrano[2,3-c]pyrazole compounds. Their reactivity and synthetic importance were investigated. In this context, recent progress in the synthesis and use of enaminonitriles of pyrano[2,3-c]pyrazole as precursors for heterocyclic compounds is reviewed. The synthetic routes for preparation of enaminonitriles are based on multicomponent reactions including three- or four-component reactions. Enaminonitriles can be used as building blocks for carbocyclic five-, six-, and seven-membered heterocycles as well as fused heterocyclic compounds. The bibliography includes 94 references. [ABSTRACT FROM AUTHOR]

The coordination chemistry of a bis(3-hydroxypyran-4-one) containing two bidentate moieties was investigated with iron and copper. The affinity of this ligand for iron was determined by spectrophotometric titration. Using electrospray ionization mass spectrometry, it was established that this bis(hydroxypyranone) derivative does not function as a tetradentate ligand, but rather bis-bidentate, forming multinuclear species, with bridged structures. The major iron species under slightly basic conditions are the multiiron complexes Fe2L3, [Fe3L3]2+,and [Fe3L3(LH)]2+. In contrast speciation with copper is relatively simple, only two species are observed, Cu(LH)2and Cu2L2. [ABSTRACT FROM AUTHOR]

An efficient,general, and atom-economic procedure for the synthesis of 2-amino-6 methyl-4-aryl-8-[(E)-arylmethylidene]-5, 6, 7, 8-4H-pyrano [3, 2-c]pyridine-3-carbonitriles has been developed by reaction of 3,5-bis[(E)-arylmethylidene]-tetrahydro-4(1H)-pyridinones with malononitrile. The reaction proceeds under green media (EtOH/H2O, 1:1) and in the presence of diammonium hydrogen phosphate (10%) or piperidine (10%) to afford pyranopyridines at room temperature with good high yields. [ABSTRACT FROM PUBLISHER]

Simple and efficient method for the synthesis of substituted furo- and pyrano-carbazole derivatives from 1-hydroxycarbazoles was described. [ABSTRACT FROM AUTHOR]