Pyran Compounds Research Articles

New thallium(I) ion selective electrode based on indeno pyran compound

Thallium(I) ion selective sensor based on 2′-amino-1,3,5′-trioxospiro[indane-2,4′(5′H)-3′-cyano-indeno(1,2-b)]pyran as a novel ionophore has been prepared and studied. This sensor displays a rapid and linear response for thallium(I) ion over the concentration range 0.1–1.0×10−6moll−1 TlNO3 with a Nernstian slope of 59mV per decade. It has a fast response time of about 5s. The sensor response is stable for at least 3 months and shows a high selectivity, stability and reproducibility. The nature of the indeno pyran ionophore and its thallium(I) complex is examined using Fourier-transform infrared analysis, elemental analysis, X-ray fluorescence and X-ray diffraction techniques. The present electrode is successfully applied to thallium(I) assays in human urine and can be used as an indicator electrode in potentiometric titrations.

Three‐Step One‐Pot Organobismuth‐Mediated Synthesis of Benzo[b]pyran Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Analysis of volatile compounds of rosemary honey. Comparison of different extraction techniques

The analysis of the volatile fraction from honey requires the sugar matrix to be separated prior to the analysis by GC-MS. In this study, three extraction techniques, simultaneous extraction-distillation, liquid-liquid extraction and solid-phase extraction, were compared to the extraction of the volatile compounds of a rosemary honey. Analysis of these fractions by gas chromatography—mass spectrometry enabled the tentative identification of up to 122 volatile compounds (alcohols, ketones, aldehydes, acids, esters, terpenes, hydrocarbons, phenol, furan and pyran compounds). SDE extracts were rich in terpenes and esters, while the other two techniques avoided the formation of artefacts due to heating the sample.

Three-step one-pot organobismuth-mediated synthesis of benzo[ b]pyran compounds

Tris[ ortho-chloromethylphenyl]bismuth diacetate reacted with phenols and enolisable substrates in the presence of a base to afford good yields of oxaphenanthrene derivatives.

REACTIONS WITH PHOSPHACUMULENES: SYNTHESIS OF PYRAN DERIVATIVES FROM THE REACTION OF N-PHENYLIMINOKETENYLIDENE TRIPHENYL-PHOSPHORANE WITH α,β-UNSATURATED CARBONYL COMPOUNDS

Abstract 2-Benzylidene-1,3-indanedione (2), 4-benzylidene-1,2-diphenyl-3,5-pyrazolidenedione (4) and/or 5-benzylidenebarbituric acid (6) can be converted by reaction with N-phenyliminoketenylidene triphenylphosphorane (1) into pyransubstituted phosphoranes 3, 5 and 7. The structure of the new cyclic imino-phosphoranes 3, 5 and 7 was confirmed on the basis of elemental analysis and spectral studies. Moreover, when Wittig reaction was carried out on the pyran compound 7, using p-nitrobenzaldehyde, the new olefin 8 was isolated.

ChemInform Abstract: Chemistry of Di‐ and Tetrahydropyrans. Part 5. The Ritter Reaction in the Series of Pyran Compounds.

AbstractDie Ritter‐Reakton der 4‐Methyl‐5,6‐dihydropyrane (I) oder der 4‐Methylen‐tetrahydropyrane (IV) mit den Nitrilen (II) liefert die 4‐Methyl‐ 4‐acylaminotetrahydropyrane (III).

Cyclocondensation of F-2-methyl-2-pentene with activated methylene compounds using ‘freeze-dried’ potassium fluoride

The reactions of F -2-methyl-2-pentene with activated methylene compounds such as acetylacetone, ethyl acetoacetate, benzoylacetonitrile, and benzoylmethyl perfluoroalkyl ketones in the presence of potassium fluoride were carried out. Each reaction proceeded smoothly in acetonitrile at room temperature by using ‘freeze-dried’ potassium fluoride as a condensing agent. Acetylacetone and ethyl acetoacetate gave both divinyl ether and pyran compounds, whereas other activated methylene compounds afforded only pyrans in good yields.

Pyran and Polyribonucleotides: Differences in Biological Activities

Maleic anhydride-divinyl ether copolymer (pyran) and the polyribonucleotides are both large polyanions with potent antiviral activity. However, they are biologically quite different. Interferon levels of 100 units or more/ml were associated with antiviral activity of polyribonucleotides. Interferon induction by pyran compounds was not primarily involved in antiviral resistance because preparations that did not induce interferon possessed antiviral activity equal to that of interferoninducing preparations. Both polyriboinosinic-cytidylic acid [poly (rI.rC)] and pyran increased the immune response to sheep erythrocytes in the Jerne hemolytic plaque-forming cell (PFC) assay, but their modes of immunoadjuvant action differed. On peak day, poly (rI.rC)-treated mice demonstrated 5.1 x 10(4) PFC/spleen (557 PFC/10(6) nucleated cells) and pyran-treated mice exhibited 4.5 x 10(4) PFC/spleen (299 PFC/10(6) nucleated cells), as compared with 2.7 x 10(4) PFC/spleen (261 PFC/10(6) nucleated cells) in controls. The compounds also differed in phagocytic alteration; polyribonucleotides did not affect phagocytosis whereas pyran produced a biphasic response. Both polyanions exhibited toxic inhibition of liver microsomal enzyme metabolism of type I and type II drugs. However, whereas pyran sensitized mice 50-fold to the lethal effects of endotoxin, the polyribonucleotides did not significantly sensitize mice to endotoxin.

Research into analogs of pyran and related compounds

Research into analogs of pyran and related compounds

Research into analogs of pyran and related compounds

Research into analogs of pyran and related compounds

Research into analogs of pyran and related compounds

The reaction of 2-methoxycarbonyl-4, 4-dichloro-2-chromene with 1-piperidino-1-cyclohexene, for example, shows the high alkylating ability of 4, 4-dichlorochromenes toward enamines. In this case, the reaction is accompanied by the transfer of the reaction center in the dichloro compound from the 4-to the 2-position (allyl rearrangement), resulting (after acid hydrolysis) in the formation of 2-methoxycarbonyl-2-(2′-oxo-1′-cyclohexyl)-4-chloro-3-chromene in two diastereoisomeric pairs (IIa and b). The structure of compounds IIa and b is proved by hydrogenation to the diastereoisomeric 2-methoxycar-bonyl-2-(2′-oxo-1′-cyclohexyl) chromans (IIIa and b) and examination of the NMR spectra of the latter. Hydrazides (IVa and b) were obtained from IIa and b, compound IVb then being cyclized to the intramolecular acylhydrazone V, which provides additional support for the structure II.

Studies on pyran, its analogs, and related compounds

Studies on pyran, its analogs, and related compounds

Pyran, its analogs, and related compounds

The effect of amines (benzylamine, N,N-dimethylethylenediamine, and ethylenediamine) on the tert-butyl ester (I) and tert-butyl amide (II) of chromone-2-carboxylic acid was studied. In contrast to the sterically unhindered derivatives of chromone-2-carboxylic acid, I and II do not undergo amidation or transamidation by reaction with the amines but are converted directly to pyran-ring-opening products. In the case of ethylenediamine, further intramolecular cyclization also occurs to form 5-(o-hydroxyphenyl)-7-carboxy-1,4-diaza-4,6-cycloheptadiene derivatives (VII and IX).

Investigations on pyran and related compounds

A convenient method for obtaining 4-aminocoumarins by the reaction of 4-chlorocoumarin with amines in dimethyl sulfoxide is proposed. The reactions of 4-chlorocoumarin with CD3ONa in CD3OD and with [N-D1]piperidine, of [3-D1]-4-chlorocoumarin with CH3ONa in CH3OH and with aniline and n-butylamine and of 4-methoxycoumarin with CD3ONa in CD3OD have been studied and the mechanism of nucleophilic and substitution in position 4 of the coumarin system is discussed.

Investigation on pyran and related compounds

Investigation on pyran and related compounds

Studies on pyran, its analogs, and related compounds

The bromination of 6,7-dibenzyloxy-4-methylcoumarin has given 6,7-dibenzyloxy-3-bromo-4-methylcoumarin and this has been converted by the Perkin reaction into 5, 6-dibenzyloxy-3-methylbenzofuran and its 2-carboxy derivative. 5, 6-Dihydroxy-3-methylbenzofuran-2-carboxylic acid has been synthesized by the catalytic debenzylation of the latter compound.

Studies in pyran, its analogs, and related compounds

Studies in pyran, its analogs, and related compounds

4H-Pyran-2,6-dicarboxylate as a Substitute for Dipicolinate in the Sporulation of Bacillus megaterium

Abstract 4H-Pyran-2,6-dicarboxylic acid, an analogue of dipicolinic acid, has been shown to completely replace dipicolinic acid in restoring normal sporulation to an aspartic semialdehyde pyruvate-condensing enzyme-less (hence dipicolinate-less) mutant of Bacillus megaterium. A large number of other, related, compounds were unable to replace dipicolinic acid. In the case of the pyran compound, the mutant culture invariably produced spores with a higher density and greater heat stability than in the presence of dipicolinic acid. Furthermore, the sporulation rate was increased. Spores of both the wild and mutant types are destabilized by lysozyme without prior treatment.