Showing papers on "Pyran published in 2002"
TL;DR: In this article, an aqueous smoke flavouring from oak (Quercus sp.) sawdust was obtained on the laboratory scale and its qualitative and quantitative composition was studied by gas chromatography.
134 citations
TL;DR: In this paper, the Pd-catalyzed alkynylzinc-β-haloacrylic acid coupling with 5-10 mol% of ZnBr2 can produce 6-alkyl-2H-pyran-2-ones (2 ) along with minor amounts of (Z)-5alkylidenefuran-2(5H)-ones (3 ) in >90% combined yields, with often very high pyranone/furanone ratios.
88 citations
TL;DR: This sequences allows for the asymmetric convergent union of two aldehydes with silyl-stannane reagent 1 in a two-step process: catalytic asymmetric allylation of the first aldehyde using 1 with a BITIP catalyst, followed by reaction of the alcohol so obtained with a second alde Hyde and TMSOTf.
72 citations
TL;DR: Nucleophilic addition of organozincs to 1,2-dihydropyranyl acetates represents a new, broadly defined method for the stereocontrolled synthesis of alpha-substituted pyrans.
56 citations
TL;DR: A mixture of cyclopropylideneacetic acids (or esters) and CuBr(2) (or CuI/I(2)) in aqueous acetonitrile afforded 4-substituted 2(5H)-furanones or 5,6-dihydro-2H-pyran-2-ones in moderate to good yields.
55 citations
TL;DR: The disagreement between the experiment and the theory concerning the heat of formation and the electronic nature of the isobenzene 2 is resolved by demonstrating that the experimental data can provide only an upper limit of the DeltaH(f) degrees value.
Abstract: The six-membered cyclic allenes given in the title have been studied theoretically by means of an MR-CI approach. For all compounds, the allene structures were found to be the ground states in the gas phase. In the cases of cyclohexa-1,2-diene (1), the isobenzene 2, and the isonaphthalene 7, the most stable structures having a planar allene moiety are the diradicals 1b, 2b, and 7b, representing the transition states for the racemization of 1a, 2a, and 7a and being less stable than the latter by 14.1, 8.9, and 11.2 kcal/mol, respectively. At variance with this order, the 3δ2-pyran 4 and the chromene 5 have the zwitterions 4c and 5c as the most stable planar structures, which lie only 1.0 and 5.4 kcal/mol above 4a and 5a, respectively. According to the simulation of the solvent effect, 4c even becomes the ground state of 4 in THF solution. The frontier orbitals of the respective states of 2 and 4 suggest different rates and sites for the reaction with nucleophiles. For the first time, the pyran 4 has been g...
54 citations
TL;DR: The alkoxy radical generated by reaction of 3,7-anhydro-2-deoxyoctitols with (diacetoxyiodo)benzene (DIB) and iodine abstracts regioselectively either the proton at C7 or that at C4 depending on the electronegativity of the substituent at C3.
51 citations
TL;DR: In this article, a synthesis of mono-, di-and tri-substituted pyran-4-ones from isoxazoles is reported, which undergo a reductive cleavage reaction with Mo(CO) 6 to generate enamino ketone intermediates.
51 citations
TL;DR: In this article, the molecular and crystal structure of 2-amino-3-cyano-6-hydroxy-4-phenyl-4H-benzo[f]chromene was established by X-ray diffraction analysis.
Abstract: Substituted 2-aminochromenes were synthesized by three-component condensation of aromatic aldehydes, derivatives of cyanoacetic acid, and phenols or naphthols. The molecular and crystal structure of 2-amino-3-cyano-6-hydroxy-4-phenyl-4H-benzo[f]chromene was established by X-ray diffraction analysis.
43 citations
TL;DR: In this article, a series of novel naphthopyrans containing fluorine substituents has been prepared and their behaviour following irradiation with UV light has been investigated, and the spectral properties of the resulting coloured naphthalene-based dienones are discussed.
41 citations
TL;DR: In this article, a convergent total synthesis of dysiherbaine was achieved by an alkylation at the γ-carbon of a protected glutamate with a highly substituted pyran derived from mannose.
Abstract: A convergent total synthesis of the marine natural product dysiherbaine was accomplished. The key steps of the synthesis are an alkylation at the γ-carbon of a protected glutamate with a highly substituted pyran derived from mannose, which was followed by a ring-contraction cascade reaction, which simultaneously gave the tetrasubstituted carbon and the hexahydrofuro[3,2-b]pyran ring system of the natural product.
TL;DR: The coupling of Fischer carbene complexes with 3-alkynyl-2-heteroaromatic carboxaldehyde derivatives has been examined in this paper, and the reaction affords pyrones fused to furans or thiophenes in a single step.
Abstract: The coupling of Fischer carbene complexes with 3-alkynyl-2-heteroaromatic carboxaldehyde derivatives has been examined. The reaction affords pyrones fused to furans or thiophenes in a single step. The compounds are stable enough for isolation. If the carbene complex features a remote alkene substituent, a subsequent Diels-Alder reaction can occur. This reaction has been used as the key step in the synthesis of a naturally occurring cadinene derivative.
TL;DR: Indium trichloride (InCl 3 ) and triphenyl phosphonium perchlorate (TPP) were found to be effective catalysts for the cyclization of o -hydroxyaldimines with 3,4-dihydro-2 H -pyran and 2,3-dhydrofuran at ambient temperature to afford novel pyrano and furanobenzopyran derivatives in excellent yields with high diastereoselectivity as mentioned in this paper.
TL;DR: In this paper, the 1:1 zwitterionic intermediate generated from dimethyl acetylenedicarboxylate and isocyanide is intercepted with 2-hydroxy-1,4-naphthoquinone, 4-hydroxymethylquinolinone and 1 naphthol in one-pot to give pyran annulated heterocyclic systems in good yields.
Abstract: The 1:1 zwitterionic intermediate generated from dimethyl acetylenedicarboxylate and isocyanide is intercepted with 2-hydroxy-1,4-naphthoquinone, 4-hydroxycoumarin, 4-hydroxy-1-methylquinolinone, 4-hydroxy-6-methylpyrone, and 1-naphthol in one-pot to give novel pyran annulated heterocyclic systems in good yields.
TL;DR: In this article, a synthetic approach to the C3-C15 segment of the cytotoxic marine metabolite phorboxazoles is described, which consists of a methylene linked bisoxane structure.
TL;DR: A series of diazoketones bearing remote benzyl or allyl ethers was subjected to a variety of conditions for catalytic diazodecomposition and cyclic oxonium ylide formation as a possible method for polycyclic ether synthesis as discussed by the authors.
TL;DR: The reactive 1 ∶ 1 intermediate produced in the reaction between alkyl or aryl isocyanides and dialkyl acetylenedicarboxylates was trapped by 3-methylcyclopentane-1,2,4 trione to yield highly functionalized tetrahydrocyclopenta[b]pyran derivatives in excellent yields as discussed by the authors.
Abstract: The reactive 1 ∶ 1 intermediate produced in the reaction between alkyl or aryl isocyanides and dialkyl acetylenedicarboxylates was trapped by 3-methylcyclopentane-1,2,4-trione to yield highly functionalized tetrahydrocyclopenta[b]pyran derivatives in excellent yields.
TL;DR: The 1,3-dipolar cycloaddition of aryl (or benzyl) azides with 1,1,trifluoro-4-ethoxy-3-butene-2-one proceeded smoothly by heating without solvent as mentioned in this paper.
TL;DR: The biochemical properties of flavonoid acetates, such as irreversible activation of NADPH cytochrome C reductase and microsome-catalyzed aflatoxin B(1) binding to DNA in vitro were found to be in tune with their specificity to TA.
TL;DR: A novel method for the synthesis of formyl and hydridemethyl derivatives of 4H-PYRAN-4-ONE is described in this paper, where the authors present a novel approach for the SYNTHESIS of FORMYL and HYDROXYMETHYL DERIVATIVES.
TL;DR: In this paper, an asymmetric induction with up to 57% de has been achieved by using α,β-unsaturated aldehydes bearing asymmetric carbon center at the β-position.
TL;DR: In this article, it was established by X-ray crystallographic analysis that pyranopyrazoles exist in the 2H and not the 1H tautomeric form.
Abstract: Substituted 6-aminopyrano[2,3-c]pyrazoles were synthesized by the two-component condensation of arylidenemalononitriles and substituted 5-pyrazolones or three-component condensation of aromatic aldehydes, malononitrile, and substituted 5-pyrazolones. It was established by X-ray crystallographic analysis that pyranopyrazoles exist in the 2H and not the 1H tautomeric form.
TL;DR: A tetracyclic benzocyclopentabenzopyran-4-one was synthesized via a domino reaction involving an initial aroyl transfer as in the Baker-Venkataraman rearrangement as mentioned in this paper.
TL;DR: In this article, the regiochemical behavior of deoxy anhydrosugars, prepared in an enantioselective way starting from methyl α-d -glucopyranoside, was examined in opening reactions, both under standard and chelating conditions.
Journal Article•
TL;DR: The antimicrobial activity of the two novel coumarin derivatives, 3-cyanonaphthol[1,2-(e)]pyran-2-one and3-cyanocoumarin was determined and it showed that they are largely active against E. coli to a lesser extent against S. aureus and C. albicans.
Abstract: The antimicrobial activity of the two novel coumarin derivatives, 3-cyanonaphthol[1,2-(e)]pyran-2-one and 3-cyanocoumarin was determined. The two novel coumarin derivatives showed specific activity against most gram-positive organisms and yeast with lower activity against most gram-negative bacteria. The MIC values of compounds showed that they are largely active against E. coli to a lesser extent against S. aureus and C. albicans.
TL;DR: The preparation of a novel spirocyclic template from tert-butoxycarbonyl-4-piperidone is reported and the addition of amines to epoxides derived from 4 was determined to occur primarily at C3.
Abstract: The preparation of a novel spirocyclic template from tert-butoxycarbonyl-4-piperidone is reported. The synthesis of N-(tert-butoxycarbonyl)-1-oxa-9-aza-spiro[5.5]undec-3-ene (4) for exploratory library generation involves ketone allylation, etherification, and ring-closing metathesis (RCM) reactions. Epoxidation of the alkene formed in the RCM followed by addition of volatile amines to the epoxides led rapidly to an exploratory library of structurally novel spirocyclic amino alcohols. The addition of amines to epoxides derived from 4 was determined to occur primarily at C3.
Journal Article•
TL;DR: In this paper, the pyrazolo[1,5-a]pyrimidines were synthesized by reacting 3-dimethylamino-2-(1, 5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carbonyl)-acrylonitrile (2) with 5-amino-3, 4-substituted-1-H-pyridine.
Abstract: Some novel pyrazolo[1,5-a]pyrimidines 5a,e, 1,2,4-triazolo[1,5-a]pyrimidine 10 and benzo[4,5]imidazo[1,2-a]pyrimidine 15 could be synthesized by reacting 3-dimethylamino-2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carbonyl)-acrylonitrile (2) with 5-amino-3,4-substituted-1H-pyrazoles 3a-e, 3-amino-1,2,4-triazole 9 and 2-aminobenzimidazole 12 respectively. The reaction of 2 with 2-benzimidazolylacetonitrile (17) afforded the benzo[4,5]imidazo[1,2-a]pyridine 18. On the other hand, the reaction of 2 with hydrazine, phenylhydrazine, malononitrile dimer and ethyl cyanoacetate dimer produced the pyrazoles 22, 23, the pyridine 26 and the pyrone 28, respectively.
TL;DR: In this article, an innovative and convenient one-pot synthesis of unsymmetrical macrocyclic biaryls (3, 5 and 8), dibenzo[a,c]cycloheptenes (10), 3,4-dihydro-2(1H)-naphthones (15), tetrahydroisoquinolines (18), dihydro-1H-isothiochromenes (20), benzo[c]thiochromene (22), and 2,3-dioxioxioxox
Abstract: An innovative and convenient one-pot synthesis of unsymmetrical macrocyclic biaryls (3, 5 and 8), dibenzo[a,c]cycloheptenes (10), 3,4-dihydro-2(1H)-naphthones (15), tetrahydroisoquinolines (18), dihydro-1H-isothiochromenes (20), benzo[c]thiochromenes (22) and 2,3-dihydro-1-benzothiophenes (24) is described. These compounds are obtained through base-catalyzed ring transformation reactions of suitably functionalized 2H-pyran-2-ones (1,6) by a carbanion, generated from
cycloalkanone (2,4,7), benzosuberone (9), cyclohexanedione monoketal (12), 4-piperidone (17), tetrahydrothiopyran-4-one (19), thiochroman-4-one (21) or tetrahydrothiophene-3-one (23).
TL;DR: Tris[ortho-chloromethylphenyl]bismuth diacetate reacted with phenols and enolisable substrates in the presence of a base to afford good yields of oxaphenanthrene derivatives as discussed by the authors.