A Conventient Synthesis of 3-Hydroxy-4-chromanone Using Iodobenzene Diacetate

A useful synthesis of 3-hydroxy-4-chromanone (6) is not currently available. Lead tetraacetate oxidation of 4-chromanone (4) yields the C(3) acetoxy derivative but this compound could not be deacetylated to 6.¹ Recently Donnelly and Maloney reported² that the Algar-Flynn-Oyamada reaction (H₂O₂/CH₃OH/NaOH), which is commonly used for the conversion of o-hydroxychalcones (1) into 3-hydroxyflavanone (2) and 3-hydroxyflavones (3), does not yield 6 when applied to o-hydroxya-crylophenone 1 (R = H). The authors found that under less basic conditions using K₂CO₃ some 6 is formed but the major product is catechol. These observations clearly indicate the necessity of developing a method for making 6. The present note describes a staightforward way of preparing 3-hydroxy-4-chromanone (6) in good yield.     

The conducting polymer electrolyte based on polypyrrole-polyvinyl alcohol and its application in low-cost quasi-solid-state dye-sensitized solar cells

The effect of polypyrrole (PPy) on the polyvinyl alcohol (PVA)-potassium iodide (KI)-iodine (I₂) polymer electrolytes has been investigated and optimized to use in a dye-sensitized solar cell (DSSC). The different weight ratios of PVA: PPy (93: 2, 91: 4, 89: 6, 87: 8, and 85: 10 wt%) polymer electrolytes (PE) were prepared by solution casting. Structural, complex formation and surface roughness of the prepared electrolytes was confirmed by X-ray diffraction, FTIR, and atomic force microscopy (AFM) respectively. Conductivity plots of all polymer films showed increasing trend with temperature and concentration of PPy. The activation energy of the optimized system found to be 0.871 kJ mol^?1. UV-visible spectrum was adopted to characterize the absorption spectra of the material revealed that increase in the absorbance with increasing PPy content and shifting the absorbance maximum towards lower energy. The indirect band gap decreased from 3.78 to 2.14 eV and direct band gap decreased from 3.88 to 2.71 eV. The EIS analyses revealed the lower charge transfer resistance of 3.029 Ω cm² at the interface between CE and PE. The excellent performance was observed in the fabricated DSSCs using PVA (85%)/PPy (10%)/KI (5%)/I₂ polymer electrolyte with a short-circuit current density of 11.071 mA cm^?2, open-circuit voltage of 0.644 V, fill factor of 0.575, and photovoltaic conversion efficiency of 4.09% under the light intensity of 100 mW cm^?2. Hence, the PPy content in polymer electrolyte influences the remarkable performance of low-cost DSSC.     

One-pot three-component azide-alkyne cycloaddition: Synthesis of new pyrazole, 1,2,3-triazole,and oxadiazole tethered and their anti-inflammatory,quantitative structure-activity relationship,and docking studies

A simple and efficient one-pot three-component azide-alkyne cycloaddition of 5-chloro-1-phenyl-pyrazole-4-carbaldehyde with 2-(prop-2-yn-1-ylthio)-5-(substituted phenoxy)methyl-1,3,4-oxadiazole and sodium azide is reported. The newly synthesized compounds were characterized by spectral and analytical data. They were screened for in vitro anti-inflammatory activity by bovine serum albumin denaturation assay. All the tested compounds showed moderate anti-inflammatory activity, whereas three compounds ( 4d , 4i , and 4k ) showed excellent activity comparable with that of the standard drug diclofenac sodium. The quantitative structure-activity relationship (QSAR) study was carried out for anti-inflammatory activities of the synthesized compounds and developed a QSAR model. Inspired by their in vitro anti-inflammatory activities, they were docked to the active site of COX-2 to know the anti-inflammatory potency in silico.     

In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer

Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au or fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL), using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from such molecules as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces. Analysis of the modified surfaces was performed in situ by Cs⁺ secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as that used to mass select the primary ions for SL. Soft-landing times as short as 30 s provided surfaces that yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were generated in an attached reaction chamber into which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor-phase chlorotrimethylsilane before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way to characterize the products produced by either technique.     

In vitro studies of carbon fiber microbiosensor for dopamine neurotransmitter supported by copper-graphene oxide composite

A composite was prepared from copper and graphene oxide (Cu-GO) by in-situ chemical reduction of a mixture containing GO and Cu(II) ions with potassium borohydride. The morphology and structure of the composite were confirmed by various physicochemical techniques. The materials were used in a tyrosinase-based microbiosensor where the enzyme is immobilized in a biocompatible matrix consisting of poly(ortho-phenylene diamine) and Cu-GO. The composite was deposited on the surface of an 8-μm thick carbon fiber microelectrode. The role of each component in the sensing layer was systematically investigated with respect to the analytical performance of the system. In its optimal configuration, the biosensor demonstrated (a) a sensitivity of 6.1?±?3 nA mM^-1 dopamine (DA), (b) a linear response to DA (with a Michaelis-Menten constant of 0.29?±?0.03 mM), (c) good selectivity over ascorbic acid and uric acid, and (d) a high blocking capacity (112.2?±?2 mM) for ascorbic acid.

The Role of Methoxy Group in the Nazarov Cyclization of 1,5-bis-(2-Methoxyphenyl)-1,4-Pentadien-3-one in the Gas Phase and Condensed Phase

ESI-protonated 1,5-bis-(2-methoxyphenyl)-1,4-pentadien-3-one (1) undergoes a gas-phase Nazarov cyclization and dissociates via expulsions of ketene and anisole. The dissociations of the [M + D]⁺ ions are accompanied by limited HD scrambling that supports the proposed cyclization. Solution cyclization of 1 was effected to yield the cyclic ketone, 2,3-bis-(2-methoxyphenyl)-cyclopent-2-ene-1-one, (2) on a time scale that is significantly shorter than the time for cyclization of dibenzalacetone. The dissociation characteristics of the ESI-generated [M + H]⁺ ion of the synthetic cyclic ketone closely resemble those of 1, suggesting that gas-phase and solution cyclization products are the same. Additional mechanistic studies by density functional theory (DFT) methods of the gas-phase reaction reveals that the initial cyclization is followed by two sequential 1,2-aryl migrations that account for the observed structure of the cyclic product in the gas phase and solution. Furthermore, the DFT calculations show that the methoxy group serves as a catalyst for the proton migrations necessary for both cyclization and fragmentation after aryl migration. An isomer formed by moving the 2-methoxy to the 4-position requires relatively higher collision energy for the elimination of anisole, as is consistent with DFT calculations. Replacement of the 2-methoxy group with an OH shows that the cyclization followed by aryl migration and elimination of phenol occurs from the [M + H]⁺ ion at low energy similar to that for 1.

Chemical Synthesis Elucidates the Immunological Importance of a Pyruvate Modification in the Capsular Polysaccharide of Streptococcus pneumoniae Serotype 4

Carbohydrate modifications are believed to strongly affect the immunogenicity of glycans. Capsular polysaccharides (CPS) from bacterial pathogens are frequently equipped with a pyruvate that can be placed across the 4,6‐, 3,4‐, or 2,3‐positions. A trans‐2,3‐linked pyruvate is present on the CPS of the Gram‐positive bacterium Streptococcus pneumoniae serotype 4 (ST4), a pathogen responsible for pneumococcal infections. To assess the immunological importance of this modification within the CPS repeating unit, the first total synthesis of the glycan was carried out. Glycan microarrays containing a series of synthetic antigens demonstrated how antibodies raised against natural ST4 CPS specifically recognize the pyruvate within the context of the tetrasaccharide repeating unit. The pyruvate modification is a key motif for designing minimal synthetic carbohydrate vaccines for ST4.     

Fe(0)-mediated synthesis of tri- and tetra-substituted olefins from carbonyls: an environmentally friendly alternative to Cr(II)

Fe(0) was investigated as a cost-effective, environmentally friendly alternative to Cr(II) for the olefination of carbonyls by activated polyhalides. In many instances, Fe(0) was equivalent or superior to Cr(II). Notably, Fe(0), but not Cr(II), proved compatible with a wide range of functionality, inter alia, unprotected phenol, aryl nitro, carboxylic acid, and alkyl nitrile. A surprising reversal of stereoselectivity for aldehydes versus ketones was observed using both metals. The resultant alpha-halo-alpha,beta-unsaturated or alpha,beta-unsaturated carboxylic acids, esters, and nitriles are common structural elements in numerous compounds of interest as well as key intermediates in the preparation of other functionality.     

Electrosynthesis of cyclic carbonates from epoxides and atmospheric pressure carbon dioxide

The use of CO(2) for the preparation of value-added compounds has dramatically increased due to increased global warming concerns. We herein report an electrochemical cell containing a copper cathode and a magnesium anode that effectively converts epoxides and carbon dioxide to cyclic carbonates under mild electrochemical conditions at atmospheric pressure.