Showing papers on "Pyran published in 1986"

Products from furans. 4. Selective oxidation of 2-furfuryl alcohol derivatives, in the presence of aryl thioethers, with N-bromosuccinimide (NBS). A new procedure for the preparation of 2H-pyran-3(6H)-ones

Abstract: Etude de l'oxydation par le NBS de l'alcool α-methyl α-[phenylthio-4 phenyl] furylique et de ses sulfoxyde et sulfone en hydroxy-6 dihydro-3,5 methyl-2 phenyl-4' phenyl-2 pyrannone-3 et sulfoxyde et sulfone

A Convenient Synthetic Method for β-Alkoxy- and β-Phenoxyacrylic Acids and 3,4-Dihydro-2H-pyran-5- and 2,3-Dihydrofuran-4-carboxylic Acids

Abstract: Hydrolyse basique d'alcoxy- et phenoxy-4 trihalogeno-1,1,1 butene-3ones-2 en les acides acryliques du titre; de la meme facon, synthese des heterocycles du titre a partir des trihalogenoacetyl-5 dihydro-3,4 pyrannes et trihalogenoacetyl-4 dihydro-2,3 furannes

Mutagenicity of K-region derivatives of 1-nitropyrene; remarkable activity of 1- and 3-nitro-5H-phenanthro[4,5-bcd]pyran-5-one.

Abstract: The mutagenic activities toward S. typhimurium strains TA98 and TA100 of K-region derivatives of 1-nitropyrene and pyrene were determined. The compounds tested were trans -4,5-dihydro-4,5-dihydroxy-1-nitropyrene (Compound 3), trans -4,5-dihydro-4,5-dihydroxypyrene (Compound 4), 1-nitropyrene-4,5-quinone (Compound 5), 1-nitropyrene-9,10-quinone (Compound 6), pyrene-4,5-quinone (Compound 7), and the lactones, 1-nitro-5 H -phenanthro[4,5- bcd ]pyran-5-one (Compound 8), 3-nitro-5 H -phenanthro[4,5- bcd ]pyran-5-one (Compound 9), and 5 H -phenanthro[4,5- bcd ]pyran-5-one (Compound 10). Neither pyrene nor any of its K-region derivatives was mutagenic, either in the absence or presence of S9 mix at the doses tested. Of the K-region derivatives of 1-nitropyrene, the lactones (Compounds 8 and 9) were generally the most active; 0.25 μg/plate induced 900–2200 revertants in TA98 or TA100 without activation. The 4,5-dihydrodiol (Compound 3), an established mammalian metabolite of 1-nitropyrene, was less mutagenic than was 1-nitropyrene in TA98, but was more mutagenic than was 1-nitropyrene in TA100, regardless of the presence of S9 mix. The quinones (Compounds 5 and 6) were less mutagenic than was 1-nitropyrene in the absence of S9 mix in both strains, but their activities were increased in the presence of S9 mix. The mutagenic activities of the lactones (Compounds 8 and 9) were lower in strains TA98NR and TA98/1,8-DNP 6 than in TA98, indicating that nitro-reduction and esterification are involved in their activation. The results of this study indicate that K-region derivatives of 1-nitropyrene may be important in its metabolic activation.

Organic synthesis using carbon monoxide. Regiospecific cobalt mediated synthesis of 2H-pyran-2-ones.

Abstract: Synthese des composes du titre a partir de Co(CO) 4 − et de cyclopropenylium via les η 3 -oxocyclobutenyl complexes de cobalt carbonyle

Studies on Heterocyclic Enamines: New Synthesis of Pyrano[2,3-b]pyndine, Pyrano[2,3-d]pyrimidine and Pyrano[2,3-c]pyrazole Derivatives

Abstract: Although 2-amino-3-cyanopyrans became recently readily obtainable via Soto’s pyran synthesis [1], util­ ity of these enaminonitriles in heterocyclic synthesis has received only limited interest compared with enaminofurans [2]. In conjunction of our effort di­ rected toward exploring the synthetic potential of enaminonitriles [3 — 5], we report here a synthesis of a new enaminopyran derivative and the chemistry of this enaminonitrile. Benzylidenemalononitrile 1 reacted with ethyl acetoacetate in refluxing ethanolic triethylamine to yield a 1:1 adduct. This could be proved to be the pyran derivative 2 and not the possible intermediate Michael adduct 3 based on 'H NMR of the reaction product. Thus, *H NMR revealed the absence of sig­ nals for protons in the region 3—6, other than the methylene quartet and pyran H-4 singlet at (3 4.8 ppm. If the reaction product was the acyclic 3, a multiplet should have appeared at 6 3—6 ppm. In contrast to the observed ready reaction of 2amino-3-cyano-4,5-dihydrofurans with ethyl cyanoacetate [6], compound 2 was recovered unreacted when treated with ethyl cyanoacetate under the same reaction conditions. However, when 2 was heated at 160 °C (bath T) a product of molecular formula C19H 17N304 was obtained. Two isomeric structures were considered (cf. structures 4 and 5). Structure 4 was eliminated based on IR spectrum which revealed only one CN signal and a highly chelated NH and OH bands extending from 3500 to 2700 cm-1. M oreover, the reaction product failed to couple with

The Formation of Bridged Bicyclic 1,2,4-Trioxanes by Intramolecular Capture of β-Hydroperoxy Cations

Abstract: The 1,4-endoperoxide, prepared from 3-(4-methylnaphth-1-yl)propanal by photo-oxygenation in CH2Cl2, gave on treatment with Amberlyst-15®, 3,10b-epidioxy-2,3,4a,10b-tetrahydro-6-methyl-1H-naphtho[2,1-b] pyran in 85% yield. Its structure was determined by X-ray crystal structure analysis. The 1,2,4-trioxane moiety is locked in a twist-boat conformation with trans fusion to the parent six-membered ring. The 1,4-endoperoxides of the methyl, butyl, and phenyl ketone analogues of the aforementioned aldehyde underwent similar acid-catalyzed rearrangement to the corresponding bridged bicyclic trioxanes in 94, 47, and 48% yields, respectively.

Activated nitriles in heterocyclic synthesis: a new approach for the synthesis of pyran derivatives

Abstract: Reactions d'acetylacetone et d'acetylacetate d'ethyle avec des α-benzoyl ou α-cyano cinnamonitriles ou -furanneacrylonitriles-2: synthese d'amino-2 aryl-4 cyano (ou benzoyl)-3 methyl-6 acetyl (ou ethoxycarbonyl)-5 4H-pyrannes et d'acetyl-3 cyano-5 methyl-2 phenyl-6 aryl-4 4H-pyrannes

Pyran derivatives, process for their preparation and their use for the preparation of aliphatic alcohols

Abstract: A description is given of pyran derivatives of formula containing an additional bond in one of the positions indicated by the dashes and in which R represents a hydrogen atom or a lower alkyl radical, and of a process for their preparation and of their use for the preparation of aliphatic alcohol of formula

Aggregation Behavior of a Thermotropic Discotic Bi-4H-pyran Derivative in Solution

Abstract: A Δ4.4′-bi-4H-pyran derivative that exhibits discotic mesomorphism of the thermotropic type was observed to self-associate in solution as well as in an ethyl cellulose polymer film at concentrations in the 10−5 M range. The aggregate structure was verified and characterized by its absorption and circular dichroism spectra. The molecular aggregate displays electronic transitions in roughly the smae spectral region as the monomeric species but with drastically different relative intensities, unlike those of J aggregates. The long-wavelength electronic transitions displayed by the aggregate are 17 times more intense than the corresponding absorption due to the monomer. The strong propensity for self-association in solution appears to be related to the ability of the pyran derivative to form a discotic mesophase structure. This phenomenon is believed to be general.

Naphtho[2,3-c]pyrane und Benz[g]isochinoline aus 6-Methoxy-2H-pyran-3(6H)-on1)

Abstract: Durch Cycloaddition des Methoxy-dihydro-3-pyranons 2 mit dem Isobenzofuran 1 entsteht 3 (exo/endo), das durch Dehydratisierung, Reduktion und erneute Wasserabspaltung in das Naphtho[2,3-c]pyran 6 ubergefuhrt werden kann. Reaktion mit Ammoniumacetat/Essigsaure bildet das Benzisochinolin 7, aus dem man durch N-Alkylierung und Hydrierung das Tetrahydro-Derivat 9 gewinnen kann. Naphtho[2,3-c]pyrans and Benz [g]isoquinolines from 6-Methoxy-2H-pyran-3(6H) one Cycloaddition of the dihydromethoxy-3-pyranone 2 with isobenzofuran 1 yields 3 (exo/endo) which can be converted into naphtho[2,3-c]pyran 6 by dehydration, reduction and repeated water elimination. Reaction with ammonium acetate/acetic acid leads to the benzoisoquinoline 7. Subsequent N-alkylation and hydrogenation result in the formation of the tetrahydro derivative 9.

Reactivity of heterocyclic compounds. VI. 2,6-Diaminopyrimidine-5-carbonitriles and 3,5-Dicyanopyridones from 2-amino-4H-pyran-3, 5-dicarbonitriles

Abstract: The reaction of different 2-amino-4H-pyrans (1, 10) with guanidine affords 2,6-diaminopyrimidine derivatives (3). Treatment of the pyrans mentioned or their acetylated derivatives with trityl tetrafluoroborate does not yield pyrylium salts, and pyrid-2-one systems (8, 11, 14) are obtained from the 2-amino-4H-pyrans (1, 10, 13) on treatment with H2SO4/ethanol.

Further studies on the biosynthesis of granaticin.

Abstract: Experiments with cerulenin-inhibited cultures of S. violaceoruber showed conversion of dihydrogranaticin (II) into granaticin (I), but not vice versa, confirming an earlier conclusion that II is the biosynthetic precursor of I. Feeding of CH3(13)C18O2Na followed by 13C-NMR analysis of the product by the 18O shift method indicated the expected incorporation of 18O at carbons 1, 11 and 13 of I and showed that the oxygen of the pyran ring originates from C-3 and not from C-15. Analysis of I biosynthesized from 13C2H3COONa by 13C[1H, 2H] triple resonance NMR spectroscopy showed the incorporation of one atom of deuterium each at C-2 and C-4. C-16 carried a maximum of 2, not 3, atoms of deuterium. These results are discussed in terms of biosynthetic mechanisms.

Certain tetrahydro-furan or pyran phosphate-ethylene or propylene ammonium derivatives

Abstract: Compounds of formula (I): ##STR1## [wherein: m is 1-3; A and B are oxygen or sulfur; and one of R 1 and R 2 is C 10 -C 22 alkyl and the other is a group of formula (II). ##STR2## where: n is 2 or 3; and --NR 3 R 4 R 5 is an amino group] and salts thereof are effective anti-cancer agents.

A physical Study on the Aromaticity of 4H-Pyran-4-one, 9H-Xanthen-9-one, and related sulphur Compounds

Abstract: Dipole moment analysis of 4H-pyran-4-one and 9H-xanthen-9-one, and their sulphur analogues, and of 9H-selenoxanthen-9-one, enables a discussion on their aromaticities. In the present work, the dipole moments of tetrahydro-4H-pyran-4-one, tetrahydrothio-4H-pyran-4-one, tetrahydroseleno- 4H-pyran-4-one, 9(10H)-anthracen-9-one, 9H-xanthen-9-one, 9H-thioxanthen-9-one and 9H-selenoxanthen-9-one were measured in benzene solution at 30.0 °C.