Showing papers on "Pyran published in 2001"
TL;DR: The synthesis of new naphtho[1',2':5,6]pyrano[2,3-d]pyrimidines and related heterocycles has been reported and antimicrobial activity was shown for some of the synthesized compounds.
Abstract: The synthesis of new naphtho[1′,2′:5,6]pyrano[2,3-d]pyrimidines and related heterocycles has been reported. The key intermediate 3-amino-8-bromo-1-(p-methoxyphenyl)-1H-naphtho[2,1-b] pyran-2-carbonitrile (3c) was obtained in one pot synthesis by treating α-cyanocinnamonitrile (1c) with 6-bromo-2-naphthol (2). Antimicrobial activity was shown for some of the synthesized compounds.
111 citations
TL;DR: A series of 2-amino-5,6,7,8-tetrahydro-5-oxo-4-aryl-7,7-dimethyl-4H-benzo-[b]-pyran-3-ethylcarboxylates were synthesized by reaction of β-cyano-β-carbothoxy styrene and 5,5-dimmethyl-1,3-cyclo-hexanedione under microwave irradiation without catalyst and solvent as discussed by the authors.
67 citations
TL;DR: The reaction of the activated olefins 1 with the allylic carbonate 2, having a hydroxy group at the terminus of the carbon chain, in the presence of catalytic amounts of Pd(2)dba(3) and dppe in THF at room temperature gave the corresponding cycloaddition products, tetrahydrofuran derivatives 5, in good to very high yields.
Abstract: The reaction of the activated olefins 1 with the allylic carbonate 2, having a hydroxy group at the terminus of the carbon chain, in the presence of catalytic amounts of Pd2dba3·CHCl3 and dppe in THF at room temperature gave the corresponding cycloaddition products, tetrahydrofuran derivatives 5, in good to very high yields. The diastereoselectivities (trans/cis ratios) of the products were in the range of ca. 60−70/40−30. The reaction of 1 with the hydroxy allylic carbonate 3 in the presence of catalytic amounts of Pd2dba3·CHCl3 and (o-tolyl)3P in THF at 50 °C afforded the corresponding cycloaddition products, tetrahydropyran derivatives 6, in good to high yields. The trans/cis ratios of the products were in the range of ca. 0−40/99−80. The reaction of 1a with the hydroxy allylic carbonate 4 needed higher reaction temperatures (∼100 °C) to give the cycloaddition product, the oxepane 7a, in 31% yield with low diastereoselectivity. Next, catalytic asymmetric syntheses of tetrahydrofuran and -pyran derivati...
54 citations
TL;DR: The quinone methide generated in situ by the Knoevenagel condensation of formaldehyde and 4-hydroxycoumarin underwent facile Diels-Alder reactions with pentafulvenes to afford novel pyranocoumarins derivatives in good yields as discussed by the authors.
36 citations
TL;DR: Decarboxylation of 11 provided known 7-hydroxylentiginosine derivative 14, whereas oxidative decar boxylation gave indolizidine 15 structurally related to castanospermine.
32 citations
TL;DR: In this paper, an efficient addition of R1R2NH to unsaturated heterocycles has been achieved using palladium catalysts using deuterium labelling experiments, and the methodology was applied to the synthesis of α-amino tetrahydrofurans and pyrans.
30 citations
TL;DR: An innovative approach to the one-pot synthesis of highly functionalized 6-aryl-3-carbomethoxy-4-methylthio-2H-pyran-2-one and a carbanion generated from tetrahydrothiopyran -4-one, 4-thiochromanone, 2,3-dihydro-1-benzothiophenes, and 4-chroman one through ring-transformation reactions.
Abstract: An innovative approach to the one-pot synthesis of highly functionalized 3,4-dihydro-1H-isothiochromenes (3), 6H-benzo[c]thiochromenes (5, 6), 6H-benzo[c]chromenes (8), and 2,3-dihydro-1-benzothiop...
29 citations
TL;DR: In this article, two methods for the synthesis of 1, 3-disubstituted naphtho[2,3-c]pyran-5,10-diones, which involve the introduction of acylmethyl groups onto 2-(1-hydroxyethyl)-1,4-naphthoequinones and subsequent base and acid-induced ring closure, were developed.
28 citations
TL;DR: In this paper, the authors show that the reaction of β-chloro-α,β-unsaturated esters with internal alkynes with triethylamine and palladium complexes, bis(triphenylphosphine)palladium species in particular, to afford to 2H-pyran-2-ones.
Abstract: Heteroannulation of β-chloro-α,β-unsaturated esters with internal alkynes proceeded in the presence of triethylamine
and palladium complexes, bis(triphenylphosphine)palladium species in particular, to afford to 2H-pyran-2-ones.
Treatment of methyl (Z)-3-chloro-2-heptenoate with Pd(PPh3)4 generates [(Z)-1-butyl-2-methoxycarbonylethenyl]chlorobis(triphenylphosphine)palladium ia oxidative addition, which gives the corresponding 2H-pyran-2-one upon addition
of 4-octyne. Terminal alkynes also reacted with β-chloro-α,β-unsaturated esters, but the major products were
β-alkynylated α,β-unsaturated
esters.
27 citations
TL;DR: In this paper, the photochromic behavior of two new bichromophoric molecules (a symmetric one formed by two 3,3-diphenyl]-naphtho[2,1-b]pyran moieties, and an asymmetric one, formed by a naphthopyran and a spiro[indoline-naphthusazine] moiety) linked through an ethenic double bond has been studied.
Abstract: The photochromic behaviour of two new bichromophoric molecules (a symmetric one, formed by two 3,3-diphenyl-[3H]-naphtho[2,1-b]pyran moieties, and an asymmetric one, formed by a naphthopyran and a spiro[indoline-naphthoxazine] moiety) linked through an ethenic double bond has been studied. A model compound, where the chromene moiety is linked to a naphthalene group, was also investigated for comparison purpose. The photochemical and thermal evolution of the bichromophoric molecules were followed spectrophotometrically and by high performance liquid chromatography (HPLC). The photochromic reaction was found to be only partially photoreversible. Massive irradiation with visible light led to degradation. The reaction mechanism for these molecules containing a chromene moiety is characterised by an intermediate, which thermally evolves to different products. The quantum yield of formation and the first-order kinetic constant of the thermal evolution of the intermediate were determined. The identification of the photoproducts was helped by information from a parallel NMR study. Comparison of these results with those previously obtained on related monochromophoric and bichromophoric compounds allowed reasonable photoreaction mechanisms to be proposed.
27 citations
TL;DR: In this article, a series of new 4-(dicyanomethylene)-2-methyl-6-( p -dithylamino-styryl)-4 H -pyran derivatives were designed and their electron spectra and nonlinear optical properties were studied.
TL;DR: In this paper, a synthesis of unsymmetrical highly functionalized biaryls with an amino substituent juxtaposed with two nitrile groups in one of the phenyl rings is delineated and illustrated by the carbanion-induced ring-transformation.
Patent•
26 Jan 2001TL;DR: In this article, a novel process for producing a δ-lactone of the formula (I) using an acyl halide was proposed, where R?1, R2, R3? and X are described as intermediates.
Abstract: The present invention relates to a novel process for producing a δ-lactone of the formula (I) using an acyl halide of the formula (1) wherein R?1, R2, R3? and X are described herein, as well as novel intermediates. In particular, the present invention relates to a process for enantioselectively producing the (R)-δ-lactone.
TL;DR: The intramolecular ene reaction of the 1,6-diene on a bicyclo[3.2.1] octane framework proceeds in a highly diastereoselective manner to form a trisubstituted pyrrolidine on the pyran ring in excellent yield as discussed by the authors.
TL;DR: In this paper, the title compounds were prepared from hetero-Diels-Alder reactions of β-imino- meso-tetraphenylporphyrin derivatives with 3,4-dihydro-2 H -pyran or 2,3-dhydrofuran catalysed by lanthanum triflate.
TL;DR: In this paper, an innovative synthesis of unsymmetrical biaryls (2,6) with electronacceptor and electron-donor substituents through carbanion-induced C-C bond formation from 6-aryl-3-cyano-4-methylthio-2H-pyran-2-ones (1) and 4-sec-amino-6-aryl 2H pyran -2-ylidene (5), using aliphatic ketones as a source of carbanions, is delineated and illustrated.
Abstract: An innovative synthesis of unsymmetrical biaryls (2,6) with electron-acceptor and electron-donor substituents through carbanion-induced C–C bond formation from 6-aryl-3-cyano-4-methylthio-2H-pyran-2-ones (1) and 4-sec-amino-6-aryl-2H-pyran-2-ones (5), using aliphatic ketones as a source of carbanion, is delineated and illustrated. However, a reaction of pyran-2-ones (1) with aromatic ketones failed to yield any desired product and in lieu a new compound isolated was characterized as the corresponding (4,6-diarylpyran-2-ylidene)acetonitrile (3). The structure of two representative compounds 5h and 6q has been confirmed by single-crystal X-ray
diffraction analysis.
TL;DR: In this paper, reaction of 1-(phenylsulfenyl)-, 1-phenyl sulfinyl)-, and 1-propanones as well as 2-acetophenone with 2-(3-methyl-2-butenyloxy)- and 2-((E)-3-phenyllsulfyl-2propenyloxy)benzaldehydes yielded the corresponding Knoevenagel condensation products.
Abstract: Reaction of 1-(phenylsulfenyl)-, 1-(phenylsulfinyl)-, and 1-(phenylsulfonyl)-2- propanones as well as 2-(phenylsulfonyl)-acetophenone with 2-(3-methyl-2-butenyloxy)- and 2-((E)-3-phenyl-2-propenyloxy)-benzaldehydes yielded the corresponding Knoevenagel condensation products. The latter compounds underwent intramolecular cycloadditions affording cis-fused 2H-pyran derivatives as the major products.
Journal Article•
TL;DR: In this article, the authors proposed two other routes according to retrosynthetic analysis using RCM as shown in Scheme 1. The first pathway is employing oxazolidinone as a chiral auxiliary.
Abstract: Preparation of 3,6-dihydro-2 H-pyran in the previous communication required 2-benzenesulfonyl-3-phenyloxaziridine to introduce a hydroxy group at the α-position of carbonyl group (Eq. 1). In order to circumvent the cumbersome use of this oxaziridine reagent, we planned two other routes according to retrosynthetic analysis using RCM as shown in Scheme 1. First pathway is employing oxazolidinone as a chiral auxiliary. This methodology was implemented by Crimmins
TL;DR: In this article, a suitably protected aryllithium derivative with citral, and subsequent deprotection and cyclization was used to obtain dibenzopyran, a precursor of the tricyclic quinone.
TL;DR: The coupling of Fischer carbene complexes with 3-alkynyl-2-heteroaromatic carboxaldehyde derivatives has been examined and has been used as the key step in the synthesis of a naturally occurring cadinene derivative.
TL;DR: In this paper, the organic ligand of the cofactor of the oxomolybdoenzymes has been synthesised in the protected and masked form, 5.5, and the key steps in the conversion of the previously prepared 3, a protected 5-(2-amino-4-oxopteridin-6-yl)-4-(1,2-dihydroxyethyl)-1,3-dithiol-2-one were: formation of the pyran ring by reaction with a chloroformate giving a protected 8-am
Abstract: The organic ligand of the cofactor of the oxomolybdoenzymes has been synthesised in the protected and masked form, 5. The key steps in the conversion of the previously prepared 3, a protected 5-(2-amino-4-oxopteridin-6-yl)-4-(1,2-dihydroxyethyl)-1,3-dithiol-2-one were: formation of the pyran ring by reaction with a chloroformate giving a protected 8-amino-4-hydroxymethyl-6-(alkyloxycarbonyl)-5a,6,9,10-tetrahydro-[1,3]dithiolo[4′,5′:4,5]pyrano[3,2-g]pteridine-2,10-dione, 10, cyanoborohydride reduction of the 11,11a-imine, protection at N-11, and finally conversion of the alcohol into a protected phosphate giving 5.
TL;DR: The mechanisms as well as the influence of resonance, cyclic strain, aromatic, and polar effects on the reactivity of the calculated systems were determined.
Abstract: Nucleophilic substitutions by a hydroxide ion at vinylic carbons of methoxyethene (system A), 3-methoxypropenal (system B), 2,3-dihydro-4H-pyran-4-one (system C), and 4H-pyran-4-one (system D) were calculated by Becke's three-parameter hybrid density functional-HF method with the Lee−Yang−Parr correlation functional (B3LYP//B3LYP) and the second-order Moller−Plesset theory (MP2//B3LYP) using the 6-31+G(d) and AUG-cc-pVTZ basis sets. In addition, bulk solvent effects (aqueous solution) were estimated by the polarized continuum (overlapping spheres) model (PCM-B3LYP//B3LYP) and the polarizable conductor PCM model (CosmoPCM-B3LYP//B3LYP). The mechanisms as well as the influence of resonance, cyclic strain, aromatic, and polar effects on the reactivity of the calculated systems were determined. In the gas phase the rate-determining step of nucleophilic vinylic substitutions by a hydroxide ion may be either addition of hydroxide ion at the vinylic carbon (systems A and B) or elimination of the leaving group (s...
Journal Article•
TL;DR: Refluxing 6-aminopyrano[2,3-c]pyrazole-5-carbonitriles with formic acid afforded the corresponding quinoline-2,5(1H,6H)-diones 7 and the antimicrobial properties of the prepared compounds was screened.
Abstract: Reaction of various fused pyran compounds with formic acid was studied. Thus, refluxing 6-aminopyrano[2,3-c]pyrazole-5-carbonitriles 3 with formic acid afforded the corresponding 3-aryl-3-(5-hydroxy-3-methyl-1H-pyrazole-4-yl)propanoic acids 4. Whereas, reaction of formic acid with 2-amino-4H-1-benzopyran-3-carbonitriles 6 gave the corresponding quinoline-2,5(1H,6H)-diones 7. The study was also extended towards many spiro compounds possessing pyran residue. The antimicrobial properties of the prepared compounds was screened.
TL;DR: A facile approach for the synthesis of flavans was developed by employing a BF3·Et2O-catalyzed pyran cyclization in an aprotic polar solvent as a key step, by which concise total syntheses of (±)-7...
Abstract: A facile approach for the synthesis of flavans was developed by employing a BF3·Et2O-catalyzed pyran cyclization in an aprotic polar solvent as a key step, by which concise total syntheses of (±)-7...
TL;DR: A highly efficient, stereocontrolled synthesis of (+)-4, the common C(7-19) tricyclic spiroketal fragment of the lituarines A, B, and C (1-3), has been achieved.
TL;DR: A number of 4-[N-4′-aryloxy but 2-ynyl N-methyl amino-6-methyl pyran-2-ones (4a-g) have been prepared in excellent yields from N-(1-yloxymethylene-1,7-dimethyl- 1,2,3-trihydropyridino-[3,2-c] pyrans 5-ones) as discussed by the authors.
TL;DR: Unsubstituted 12H-benzo[b][1,7]phenanthrolin-7-ones 14 and 19, which include a pyridine nitrogen in the same 4-position as the pyran oxygen of acronycine exhibited cytotoxic activities within the same range of magnitude as acronyCine itself.
Abstract: Condensation of either 2-bromobenzoic acid (4) or 2-chloro-3-nitrobenzoic acid (5) with suitable aminoquinolines 6-8 afforded phenylquinolylamines 9-13. Acid mediated cyclization gave the corresponding 12H-benzo[b][1,7]phenanthrolin-7-ones 14 and 15, and 12H-benzo[b][1,10]phenanthrolin-7-ones 16-18. Compounds 14, 16, and 17 were subsequently N-methylated to 6-demethoxyacronycine and acronycine analogues 19-21, whereas reduction of the aromatic nitro group of 18 gave the amino derivative 22. Unsubstituted 12H-benzo[b][1,10]phenanthrolin-7-ones 16, 17, 20, and 21 were devoid of significant cytotoxic activity, whereas 18 and 22, bearing a nitrogen substituent at position 11, were significantly active. Unsubstituted 12H-benzo[b][1,7]phenanthrolin-7-ones 14 and 19, which include a pyridine nitrogen in the same 4-position as the pyran oxygen of acronycine exhibited cytotoxic activities within the same range of magnitude as acronycine itself.
TL;DR: Synthesis of GLA-60 type pyran carboxylic acid analogues with an alkyl chain instead of an ester chain and their LPS-antagonist activity toward human U937 cells are described.