Showing papers on "Pyran published in 2008"
TL;DR: Magnesium oxide (MgO) as a highly effective heterogeneous base catalyst effectively catalyzes the three component reaction of aryl aldehydes, malononitrile and α-hydroxy or α-amino activated C-H acids as mentioned in this paper.
Abstract: Magnesium oxide (MgO) as a highly effective heterogeneous base catalyst effectively catalyzes the three component reaction of aryl aldehydes, malononitrile and α-hydroxy or α-amino activated C–H acids such as 1,3-cyclohexanedione, dimedone, 4-hydroxy-6-methylpyrone, 4-hydroxycoumarin, 1,3-dimethylbarbituric acid and 1,3-dimethyl-6-amino uracil to the formation of the corresponding pyran annulated heterocyclic systems The catalyst is inexpensive and easily obtained, stable and storable, easily recycled and reused for several cycles with consistent activity
178 citations
TL;DR: Sodium selenate has been found to be an outstanding catalyst for the preparation of tetrahydrobenzo[b]pyran derivatives in aqueous media in very good yields and under entirely green and eco-friendly conditions as mentioned in this paper.
146 citations
TL;DR: Highly potent bryostatin analogues which contain the complete bRYostatin core structure have been synthesized using a pyran annulation approach as a key strategic element.
Abstract: Highly potent bryostatin analogues which contain the complete bryostatin core structure have been synthesized using a pyran annulation approach as a key strategic element. The A ring pyran was assembled using a pyran annulation reaction between a C1−C8 hydroxy allylsilane and an aldehyde comprising C9−C13. This pyran was transformed to a new hydroxy allylsilane and then coupled with a preformed C ring aldehyde subunit in a second pyran annulation, with concomitant formation of the B ring. This tricyclic intermediate was elaborated to bryostatin analogues which displayed nanomolar to subnanomolar affinity for PKC, but displayed properties indistinguishable from a phorbol ester in a proliferation/attachment assay.
86 citations
TL;DR: In this paper, an efficient and convenient approach to the synthesis of 2-amino-3-cyano-4-aryl-7,7-dimethyl-5-oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran derivatives using N-methylimidazole as the organocatalyst (20 mol%) is described.
Abstract: An efficient and convenient approach to the synthesis of 2-amino-3-cyano-4-aryl-7,7-dimethyl-5-oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran derivatives using N-methylimidazole as the organocatalyst (20 mol%) is described. This method has several advantages, such as mild conditions, high yields, and simple work-up procedure.
85 citations
TL;DR: Five indole alkaloids (naucleofficines A-E) were isolated from the stems of Nauclea officinalis and in vitro activity screening of the above seven compounds showed weak to moderate inhibitory activity against Plasmodium falciparum.
65 citations
TL;DR: An enantioselective synthesis of the Hsp90 inhibitor geldanamycin was achieved in 20 linear steps and 2.0% overall yield from 2-methoxyhydroquinone.
55 citations
TL;DR: A catalytic system used to promote the coupling between secondary propargylic alcohols and cyclic 1,3-diketones and the nature of the resulting products was found to be dependent on the ring size of the dicarbonyl compound employed.
Abstract: A catalytic system consisting of the 16-electron allyl-ruthenium(II) complex [Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6] (dppf = 1,1′-bis(diphenylphosphino)ferrocene) and trifluoroacetic acid (TFA) has been used to promote the coupling between secondary propargylic alcohols and cyclic 1,3-diketones. The nature of the resulting products was found to be dependent on the ring size of the dicarbonyl compound employed. Thus, whereas 6,7-dihydro-5H-benzofuran-4-ones have been selectively obtained starting from 1,3-cyclohexanediones, via furan-ring formation, the use of 1,3-cyclopentanedione leads instead to 6,7-dihydro-4H-cyclopenta[b]pyran-5-ones via a pyran-ring formation process.
53 citations
TL;DR: In this paper, a diastereoselective synthesis of pyranobenzopyrans and furanobensopyrants via 2 ǫ% of molecular iodine-catalyzed reaction of o -hydroxybenzaldimines with 3,4-dihydro-2 H -pyran and 2,3-dhydrofuran at ambient temperature is described.
53 citations
TL;DR: The synthesis and pharmacological evaluation of thiophene bioisosteres of the highly potent spirocyclic benzopyran 1 are detailed and the activity of 2a in the mouse capsaicin assay seems to indicate sigma 1 antagonistic activity.
Abstract: Herein, the synthesis and pharmacological evaluation of thiophene bioisosteres of the highly potent spirocyclic benzopyran 1 are detailed. The synthesis of 1-benzyl-6′-methoxy-6′,7′-dihydrospiro[piperidine-4,4′-thieno[3.2-c]pyran] (2a) was performed starting with 3-bromothiophene (3). After introduction of the acetaldehyde substructure (7), halogen metal exchange, addition of 1-benzylpiperidin-4-one, and cyclization led to the spirocyclic thienopyran 2a. The removal of the benzyl group afforded the secondary amine 2f, which was substituted with various residues. With respect to σ1 affinity the N-benzyl derivative 2a, the N-cyclohexylmethyl derivative 2d, and the N-p-fluorobenzyl derivative 2i represent the most potent compounds of this series binding with Ki values of 0.32, 0.29, and 0.62 nM, respectively. Electronic properties of the substituents have only little impact on σ1 affinity. The most potent σ1 ligands display high selectivity against σ2, 5-HT1A, 5-HT6, 5-HT7, α1A, α2, and NMDA receptors. The a...
48 citations
TL;DR: A new class of base-catalyzed Diels-Alder reactions of 2H-pyran-2,5-diones has been developed using catalytic amount of dicyclohexylmethylamine in tert-butyl alcohol with good yields and exclusive endo selectivity.
47 citations
TL;DR: A three-component reaction of an isocyanide, a dialkyl acetylenedicarboxylate, and tetronic acid in dichloromethane at room temperature afforded 4H-furo[3,4-b]pyran derivatives which have a broad spectrum of biological activity.
TL;DR: An efficient and convenient method for the synthesis of fused pyran rings via intramolecular palladium-catalysed cyclisation followed by β-H elimination or C-H activation has been developed as discussed by the authors.
TL;DR: In this paper, a seed germination stimulant was synthesized using direct and regioselective Ti-crossed aldol addition between dihydro-2 H -pyran-3(4 H )-ones and methyl pyruvate as the key step.
TL;DR: A diversity-oriented synthesis of a range of fused pyran-gamma-lactones that was effected through a versatile Pd-thiourea complex-catalyzed intramolecular alkoxycarbonylative annulation is reported.
TL;DR: Thermal generation of acylketenes in diol-containing substrates results in dual macrocyclization/pyran-hemiketal formation, and the challenging macrolactonization of a tertiary alcohol was achieved.
Abstract: Thermal generation of acylketenes in diol-containing substrates results in dual macrocyclization/pyran-hemiketal formation. This transformation expands the scope of acylketene macrolactonizations and their application to the synthesis of complex macrolides. Triol and even tetrol substrates also have been closed in highly regioselective fashion. Additionally, the challenging macrolactonization of a tertiary alcohol was achieved.
TL;DR: In this paper, a series of novel butenolides as seed germination stimulants are described, and the key steps include the cyclization reaction of enamine 4 to form a pyran ring, the efficient halogenating reaction and the selective lithiation reaction.
TL;DR: An enantioselective, convergent, total synthesis of the antiviral marine natural product (-)-hennoxazole A has been completed in 17 steps, longest linear sequence, from serine methyl ester and in 9 steps from an achiral bisoxazole intermediate.
Abstract: An enantioselective, convergent total synthesis of the antiviral marine natural product (-)-hennoxazole A is completed in 14 steps (longest linear sequence) from commercially available 4-methyloxazole-2-carboxylic acid Synthesis of the C(1)-C(15) pyran/bisoxazole fragment takes advantage of an aldol-like coupling between a dimethyl acetal and an N-acetylthiazolidinethione for the direct, stereoselective installation of the C(8)-methoxy-bearing stereocenter A one-pot acetoacetate acylation/decarboxylation/cyclodehydration of another elaborate thiazolidinethione allows for rapid assembly of the pyran-based ring system Synthesis of the C(15)-C(25) skipped triene side chain fragment makes use of a [2,3]-Wittig-Still rearrangement for efficient installation of the trisubstituted Z-double bond Key late-stage coupling of the two fragments is effected by deprotonation of the methyl group on the bisoxazole system using lithium diethylamide, followed by alkylation with an allylic bromide side chain segment to form the C(15)-C(16) bond
TL;DR: An expedient synthesis of a series of 2-pyrones, bearing a CF 3 group at the 6-position and aryl group at position 4, from readily available aries, trifluorobutane-1,3-diones, PCl 5, and sodium diethyl malonate is described.
TL;DR: In this paper, five different types of 2D-π-pyran derivatives, each having two donor (2D) and one acceptor (A) groups showed significantly large Stokes shifts.
01 Jan 2008
TL;DR: In this paper, a basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide, [bmIm]OH has been used as an efficient catalyst for the synthesis of a variety of 4H-benzo[b]pyran derivatives by a one-pot three component condensation of aldehydes, cyclohexa-1,3-diones and malononitrile/ethyl cyano acetate at room temperature.
Abstract: A basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide, [bmIm]OH has been used as an efficient catalyst for the synthesis of a variety of 4H-benzo[b]pyran derivatives by a one-pot three component condensation of aldehydes, cyclohexa-1,3-diones and malononitrile/ethyl cyano acetate at room temperature. The reactions are very fast (5-20 min), high yielding (85-98%) and do not require any organic solvent.
TL;DR: Diverse substituted 4-di(Tri)fluoromethyl-3-cyanopyridine-2(1H)-thiones were synthesized via the Claisen condensation of alpha-methyl(methylene)ketones with di(tri)fluoroacetate, and utilized in domino reactions to produce first various substituted thieno[2,3-b]pyridine and, then, thienopyridines polyannulated with
Abstract: Diverse substituted 4-di(tri)fluoromethyl-3-cyanopyridine-2(1H)-thiones were synthesized via the Claisen condensation of alpha-methyl(methylene)ketones with di(tri)fluoroacetate, followed by the immediate Thorpe-Guareschi reaction of the preformed di(tri)fluoromethyl-1,3-diketones with cyanothioacetamide. The procedure allows facile synthesis of the di(tri)flouromethylated pyridine-2(1H)-thiones in 50-95% yields, without the need for isolation and purification of intermediates. Resultant 4-di(tri)fluoromethyl-3-cyanopyridine-2(1 H)-thiones were subsequently utilized in domino reactions to produce first various substituted thieno[2,3-b]pyridines and, then, thienopyridines polyannulated with pyridine, pyrimidine, benzodiazocine, diazepine, and pyran rings.
TL;DR: Careful orchestration of the alcohol protecting groups was necessary to facilitate deprotection of alcohol functionality in the presence of the chemically sensitive polyene chain.
TL;DR: In this paper, a method for the synthesis of 2′-amino-1,2-dihydrospiro[(3H)-indole-3,4′-(4′H)-pyran]-2-ones has been suggested consisting in the three-component reaction of isatins, cyanoacetic acid derivatives, and α-methylenecarbonyl compounds (β-dicarbonyls compounds, activated phenols, and OH-substituted heterocycles) in ethanol in the presence of triethylam
Abstract: A versatile method for the synthesis of 2′-amino-1,2-dihydrospiro[(3H)-indole-3,4′-(4′H)-pyran]-2-ones has been suggested consisting in the three-component reaction of isatins, cyanoacetic acid derivatives, and α-methylenecarbonyl compounds (β-dicarbonyl compounds, activated phenols, and OH-substituted heterocycles) in ethanol in the presence of triethylamine as a catalyst. The reaction proceeds selectively to form spiro[(3H)-indole-3,4′-(4′H)-pyrans].
TL;DR: 12 overcomes CDDP resistance and induces programmed cell death with molecular features different from CDDP, suggesting that both drugs induce apoptosis through different initial pathways.
Abstract: (4-(tetrahydro-2H-pyran-2-yloxy)R1)R2-diamminedichloroplatinum(II) complexes (1−12) consisting of CDDP linked to THP via aliphatic CH2-spacers were tested in two TGCT cell lines. The most promising...
Journal Article•
TL;DR: In this article, a basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide, [bmIm]OH has been used as an efficient catalyst for the synthesis of a variety of 4H-benzo[b]pyran derivatives by a one-pot three component condensation of aldehydes, cyclohexa-1,3-diones and malononitrile/ethyl cyano acetate at room temperature.
Abstract: A basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide, [bmIm]OH has been used as an efficient catalyst for the synthesis of a variety of 4H-benzo[b]pyran derivatives by a one-pot three component condensation of aldehydes, cyclohexa-1,3-diones and malononitrile/ethyl cyano acetate at room temperature. The reactions are very fast (5-20 min), high yielding (85-98%) and do not require any organic solvent.
TL;DR: Palladium-catalyzed carbon−sulfur bond formation using modified Migita reaction conditions was explored and applied to the synthesis of a former antiasthma drug candidate, tetrahydro-4-[3]-4-(2-methyl-1H-imidazol-1-yl)phenyl]thio]phenyl-2H-pyran-4-carboxamide as discussed by the authors.
TL;DR: An efficient one-pot procedure for the synthesis of fused 2′-amino-3′-R-spiro-[indole-3,4′-pyran]-2(1H)-ones via base-catalyzed three-component condensation of isatins with the corresponding nitriles and 1,3-diketones was proposed in this article.
Abstract: An efficient one-pot procedure has been proposed for the synthesis of fused 2′-amino-3′-R-spiro-[indole-3,4′-pyran]-2(1H)-ones via base-catalyzed three-component condensation of isatins with the corresponding nitriles and 1,3-diketones.
TL;DR: In this paper, a short and stereocontrolled route to amino carbohydrate derivatives with 1,2-oxazines as crucial relay compounds was established, which can be regarded as protected 4-amino-1,4-dideoxyhex-3-ulose derivatives.
TL;DR: A transition metal-mediated, atom-economical approach toward the crucial A and D rings of miyakolide is described, utilizing an Ru-catalyzed alkene-alkyne coupling followed by a Pd-Catalyzed allylic alkylation to establish the all-cis stereochemistry.