Showing papers in "Heterocycles in 2004"
TL;DR: In this paper, a 2-Aminobenzenethiol and an aryl aldehyde were allowed to react to give 2-arylbenzothiazole in good yield in the presence of a catalytic amount of scandium triflate Sc(OTf) 3.
Abstract: 2-Aminobenzenethiol and an aryl aldehyde were allowed to react to give a 2-arylbenzothiazole in good yield in the presence of a catalytic amount of scandium triflate Sc(OTf) 3 . The detailed study showed that Sc(OTf) 3 catalyzed two steps, that is, the formation of a thiazoline ring and the oxidation of the thiazoline to a thiazole ring. This is the first example that scandium(III) ion catalyzed oxidation of an organic compound using molecular oxygen as an oxidant. The reaction was applied to o-phenylenediamine and an aryl aldehyde to give corresponding 2-arylbenzimidazole in moderate to good yields depending upon the structure of aldehyde.
135 citations
TL;DR: The exploration of β-lactone reactivity and transformations has continued since the first synthesis of these strained heterocycles by Einhorn in 1883 as discussed by the authors and has led to further developments in the area of novel transformations of (3lactones and significantly increased applications in natural product total synthesis.
Abstract: The exploration of β-lactone reactivity and transformations has continued since the first synthesis of these strained heterocycles by Einhorn in 1883. The principal reactivity modes of β-lactones include nucleophilic addition resulting in either acyl C2-O1 or alkyl C4-O1 cleavage, rearrangement leading to ring expansion, decarboxylation, and electrophilic reactions of β-lactone enolates. Recent advances in asymmetric β-lactone synthesis has led to further developments in the area of novel transformations of (3-lactones and significantly increased applications in natural product total synthesis. The latter topic is the focus of this review and covers the period inclusive to the end of 2003.
121 citations
TL;DR: In this paper, a review of different kinds of heterocyclic compounds under microwave irradiation were reviewed. But, the authors did not consider the effect of microwave radiation on the properties of the synthesized compounds.
Abstract: Microwave technique has been applied extensively in organic syntheses. In this paper, syntheses of different kinds of heterocyclic compounds under microwave irradiation were reviewed.
117 citations
TL;DR: New dioxo- or trioxopiperazine metabolites named gliocladins A-C and glioperazine have been isolated from a strain of Gliocladium sp.
Abstract: New dioxo- or trioxopiperazine metabolites named gliocladins A-C (1 - 3 ) and glioperazine (4) have been isolated from a strain of Gliocladium sp., originally separated from the sea hare. Their structures have been elucidated by spectroscopic analyses using various NMR spectroscopic techniques. Structurally unique trioxopiperazine (3) exhibited significant cytotoxicity against cultured P388 cells.
104 citations
TL;DR: In this paper, the synthesis of N-ethynyl-heterocycles by elimination, nucleophilic substitution, isomerization, benzotriazole intermediates and other methods are reviewed.
Abstract: Synthesis of N-ethynyl-heterocycles by elimination, nucleophilic substitution, isomerization, benzotriazole intermediates and other methods are reviewed. The reactions of N-ethynyl-heterocycles including additions, cycloadditions and polymerizations are discussed.
67 citations
TL;DR: A new compound named trolline was isolated from the ethanol extract of the flowers of Trollius chinensis Bunge as mentioned in this paper, which exhibited appreciable antibacterial activity against respiratory bacteria such as Staphylococcus aureus, Streptococcus pneumoniae and Klebsiella pneumoniae.
Abstract: A new compound, named as trolline was isolated from the ethanol extract of the flowers of Trollius chinensis Bunge. The chemical structure of this compound was elucidated by NMR, MS, IR, UV spectra and single-crystal X-Ray analysis. The in vitro antibacterial and antiviral experiments revealed that trolline exhibited appreciable antibacterial activity against respiratory bacteria such as Staphylococcus aureus, Streptococcus pneumoniae and Klebsiella pneumoniae. Trolline was also demonstrated to have moderate antiviral activity against influenza virus A and B.
66 citations
TL;DR: In this article, diaminochromenes (3a-f, 7a-c, and 10), 7-amino-4-aryl-coumarins (8a,b), 7hydroxy 4-aryl -1,2-dihydroquinolines (9a-b), and 2-aminos-7-hydroxy-4-(4-chlorophenyl)-4H-chromene-2-carbonitrile (16a-d) were synthesized with the addition of different substituted aminonaphth
Abstract: Some new diaminochromenes (3a-f, 7a-c, and 10), 7-amino-4-aryl-coumarins (8a,b), 7-hydroxy-4-aryl-1,2-dihydroquinolines (9a-c) and 2-amino-7-hydroxy-4-(4-chlorophenyl)-4H-chromenes (16a-d) were synthesized viu Michael addition of different substituted aminonaphthol (1), aminophenol (6), resorcinol derivatives (15a-d), chloronaphthol (17) and 4-hydroxycoumarin (19) with a-cyanocinnamonitriles (2a-c) and ethyl α-cyanocinnamate (2d-f). 2-Acetylamino-7-amino-4-(4-chlorophenyl)-4H-chromene-2-carbonitrile (14) was obtained as a unique product via hydrazinolysis of ethoxymethyleneamino derivative (13). The formation of coumarins (8a,b) and quinolines (9a-c) were anomalous case. Structures of the titled compounds cited in this article were elucidated by spectrometric data (IR, 1 H NMR, 1 3 C NMR (APT) and EMS). All of the newly synthesized compounds were evaluated for antimicrobial activities, where 16b and 16c exhibited activity against staphylococcus aureus (ATCC 25923).
58 citations
TL;DR: In this article, 2-Nitroaniline and aromatic aldehydes were coupled to give benzimidazoles in high yields in the presence of 2-bromo-2-nitropropane and indium at room temperature.
Abstract: 2-Nitroaniline and aromatic aldehydes were coupled to give benzimidazoles in high yields in the presence of 2-bromo-2-nitropropane and indium at room temperature.
58 citations
TL;DR: In this paper, the isolation and development of total syntheses of naturally occurring furocarbazole alkaloids are described, and diverse synthetic strategies which were elaborated by different research groups are discussed and compared.
Abstract: The isolation and the development of total syntheses of naturally occurring furocarbazole alkaloids are described. The diverse synthetic strategies which were elaborated by different research groups are discussed and compared.
52 citations
47 citations
TL;DR: In this paper, 2-Aminobenzenethiol and an aryl aldehyde reacted to give a benzothiazoline via an imine intermediate, which was aromatized by oxygen or hydrogen peroxide to give the high yield of 2-arylbenzothiazole in the presence of a catalytic amount of Sc(OTf) 3.
Abstract: 2-Aminobenzenethiol and an aryl aldehyde reacted to give a benzothiazoline via an imine intermediate, and the benzothiazoline was aromatized by oxygen or hydrogen peroxide to give a high yield of 2-arylbenzothiazole in the presence of a catalytic amount of scandium triflate Sc(OTf) 3 . The intermediary benzothiazoline was isolated and allowed to react with O 2 or H 2 O 2 in the presence of Sc(OTf) 3 , and the Lewis acid was found to also catalyze the oxidative process other than the ring closing step.
TL;DR: An optimized analog of prostaglandin E 2 which incorporates a γ-lactam in place of the cyclopentanone ring and which incorporates metabolically stabilized side chains, has been identified and shown to exhibit potent and selective EP4 receptor agonism.
Abstract: An optimized analog of prostaglandin E 2 which incorporates a γ-lactam in place of the cyclopentanone ring and which incorporates metabolically stabilized side chains, has been identified and shown to exhibit potent and selective EP4 receptor agonism. The compound (2) (L-000902688) is also well absorbed on oral dosing and exhibits a long half-life making it an excellent tool for the study of the role of EP4 receptor in physiology and disease. An efficient synthesis of 2 from a chiral synthon is described.
TL;DR: Peroxy containing, polyketide derived metabolites constitute a prevalent class of biologically potent metabolites from Plakortis species.
Abstract: Metabolites from the Plakortis genus of sponges are reviewed, with major focus on P. halichondrioides, P.simplex, P. angulospiculatus, P. lita, P. nigra, P. quasiamphiaster, P. zygompha, and the closely related Plakinastrella onkodes. The structures, stereochemistry, pharmacological activity and selected syntheses of these metabolites are discussed. Peroxy containing, polyketide derived metabolites constitute a prevalent class of biologically potent metabolites from Plakortis species.
TL;DR: In this article, a solvent-free microwave-assisted synthesis of trisubstituted imidazoles is reported, which is produced by condensation of α-hydroxyketone with an aldehyde over silica gel or alumina impregnated with ammonium acetate as the solid support.
Abstract: A solvent-free microwave-assisted synthesis of trisubstituted imidazoles is reported. The imidazoles are produced by the condensation of α-hydroxyketone with an aldehyde over silica gel or alumina impregnated with ammonium acetate as the solid support in short time with good yields. An air oxidation mechanism is proposed, and this clean air oxidation considerably reduces the cost of imidazole synthesis.
TL;DR: A stereoselective total synthesis of (′)-xyloketal D (′-2) has been achieved using a cycloaddition reaction of an ortho-quinone methide and a dihydrofuran as a key step.
Abstract: A stereoselective total synthesis of (′)-xyloketal D (′-2) has been achieved using a cycloaddition reaction of an ortho-quinone methide and a dihydrofuran as a key step. Preliminary model studies towards the total synthesis of xyloketal A (1) are also reported.
TL;DR: Leptosphaeria sp. originally separated from the marine alga Sargassum tortile has been elucidated on the basis of spectroscopic analyses of their acetate derivatives (6-10) using various ID and 2D NMR techniques and some chemical transformations as mentioned in this paper.
Abstract: Leptosins O (1), P (2), Q (3), R (4) and S (5) have been isolated from a strain of Leptosphaeria sp. originally separated from the marine alga Sargassum tortile. Their absolute stereostructures have been elucidated on thebasis of spectroscopic analyses of their acetate derivatives (6-10) using various ID and 2D NMR techniques and some chemical transformations. The NMR and NOE spectral analyses of 6-10 revealed that they exist in a single conformer of B type in CDCl 3 . Among these metabolites, leptosins O (1) and P (2) exhibited significant cytotoxicity against cultured P388 cells.
TL;DR: The synthesis of pyrrolo[3,2,c]quinolines is comprehesively reviewed in this paper, which is based upon the endeavors in this area by three independent groups.
Abstract: The synthesis of pyrrolo[3,2,c]quinolines is comprehesively reviewed. Synthetic approaches to martinelline alkaloids are then considered which are based upon the endeavors in this area by three independent groups.
TL;DR: In this paper, pyridinium chiral ionic liquids have been synthesized from the corresponding pyridine and chiral primary amines, and the physical properties of these salts were determined; one of the salts is a room-temperature ionic liquid thermally stable up to 215 °C.
Abstract: New pyridinium chiral ionic liquids have been synthesised from the corresponding pyridine and chiral primary amines. The physical properties of these salts were determined; one of the salts is a room-temperature ionic liquid thermally stable up to 215 °C and suitable for organic synthesis.
TL;DR: In this article, a microwave-assisted synthesis of 4(3H)-quinazolinones by the condensation of isatoic anhydride, primary amines and orthoesters in the presence of catalytic amounts of p-toluenesulfonic acidin high yields is reported.
Abstract: Efficient microwave-assisted synthesis of 4(3H)-quinazolinones by the one-pot three-component condensation of isatoic anhydride, primary amines and orthoesters in the presence of catalytic amounts ofp-toluenesulfonic acidin high yields is reported.
TL;DR: In this article, an extensive survey of both thermal and photochemical methodologies that have been applied to fluorinated oxadiazoles, and shows how molecular rearrangements can be an alternative and in some cases the most convenient route for the synthesis of several fluorinated heterocycles.
Abstract: Molecular rearrangements of O-N bond-containing azoles (1-oxa-2- azoles) represent a wide class of reactions by which various heterocycle-to- heterocycle transformations can be performed as alternative synthetic methodologies. The material presented in this review is an extensive survey of both thermal and photochemical methodologies that have been applied to fluorinated oxadiazoles, and shows how molecular rearrangements can be an alternative and in some cases the most convenient route for the synthesis of several fluorinated heterocycles.
TL;DR: Sapphyrins fused with mono-bicyclo[2.2]octadiene (BCOD) and di-BCOD units are prepared, which are converted into mono- and dibenzosappyrins by heating at 200 °C as discussed by the authors.
Abstract: Sapphyrins fused with mono-bicyclo[2.2.2]octadiene (BCOD) and di-BCOD units are prepared, which are converted into mono- and dibenzosappyrins by heating at 200 °C; soret bands are red shifted by 10-20 nm by introduction of fused benzene rings, but Q bands are not much affected in benzosapphyrins.
TL;DR: In this article, the authors converted 1H-indazoles upon reaction with carbon monoxide with [Cp*Fe(CO) 2 ] 2 as a catalyst, and showed that the resulting 1Hindazole can be converted to 1HIndazoles with carbon dioxide.
Abstract: ortho-Nitro-ketoximes are converted to 1H-indazoles upon reaction with carbon monoxide with [Cp*Fe(CO) 2 ] 2 as catalyst.
TL;DR: Isomeric 2-, 3- and 4-quinolinols (11-13) underwent selective ionic hydrogenation with cyclohexane in CF 3 SO 3 H-SbF 5 system to give 5,6,7,8-tetrahydro-2( 1 H)-quinolinone, 5, 6,7 and 8-to-8-toothhexane, 3,4-dihydro 2(1H)-quinol and 4,1H-quinol, respectively.
Abstract: Isomeric 2-, 3- and 4-quinolinols (11-13) underwent selective ionic hydrogenation with cyclohexane in CF 3 SO 3 H-SbF 5 system to give 5,6,7,8-tetrahydro-2( 1 H)-quinolinone, 5,6,7,8-tetrahydro-3-quinolinol and 5,6,7,8-tetrahydro-4(1H)-quinolinone (28-30), respectively. When reaction was carried out in the presence of excess of aluminum chloride, 11 gave 3,4-dihydro-2(1H)-quinolinone (31), whereas 13 gave the product (30). Compounds (11) and (13) condense with benzene in the presence of aluminum halides producing phenyl substituted derivatives of 28, 31 and 30 (products 32-34), respectively. The mechanism of these and related reactions involving superelectrophilic dicationic intermediates is discussed.
TL;DR: In this article, a three-step procedure from triethylorthoformate and activated methylene derivatives leading to alkoxymethylenemalonates followed by reaction with aromatic amines and finally a cyclization is described.
Abstract: Quinolones can be prepared in a three step procedure from triethylorthoformate and activated methylene derivatives leading to alkoxymethylenemalonates followed by reaction with aromatic amines and finally a cyclization. All the reactions were carried out under solvent-free conditions possibly under microwave activation with benefits for the first step.
TL;DR: In this article, a review highlighting this aspect covers literature up to 2003 and highlights the applications of 3-cinnamoyl-4-hydroxy-6-methyl-2-oxo-2H-pyrans (Chalcone analogues of DHA) in the synthesis of heterocyclic compounds.
Abstract: 3-Acetyl-4-hydroxy-6-methyl -2-oxo-2H-pyran (Dehydroacetic acid, DHA) and its simple derivatives such as 3-cinnamoyl-4-hydroxy-6-methyl-2-oxo-2H-pyrans (Chalcone analogues of DHA) find interesting applications in the synthesis of various heterocyclic compounds. The review highlighting this aspect covers literature up to 2003.
TL;DR: In this article, a TMSOTf-catalyzed condensation of a potential electrophile with a nucleophile was achieved with a high level of 3,4-trans condensation, and succeeded in the stereoselective synthesis of procyanidin B2 and its peracetate.
Abstract: TMSOTf-catalyzed condensation of a potential electrophile with a nucleophile was achieved with a high level of 3,4-trans condensation, and we succeeded in the stereoselective synthesis of procyanidin B2 and its peracetate. Studies on the inhibitory activity of the Maillard reaction of four 3,4-trans series of catechin and epicatechin dimers, procyanidin Bl, B2, B3 and B4, and their peracetates were also carried out.
TL;DR: An improved synthesis of a suitably functionalized tricyclic core of sarains was developed by adaptation of Katritzky's cycloaddition using a 3-oxidopyridinium betaine as discussed by the authors.
Abstract: An improved synthesis of a suitably functionalized tricyclic core of sarains has been developed by adaptation of Katritzky's cycloaddition using a 3-oxidopyridinium betaine.
TL;DR: In this paper, o-nitrophenols containing a CO 2 Me or OMe group on their benzene rings and N,N-diethylaniline were examined to investigate the effects of the position and electronic character of these substituents on the formation of the oxazole ring.
Abstract: o-Nitrophenols and o-nitroaniline were reacted with amines at 210-215°C to produce the corresponding benzoxazoles and benzimidazoles, respectively, in moderate yields. The reactions between o-nitrophenols containing a CO 2 Me or OMe group on their benzene rings and N,N-diethylaniline were examined to investigate the effects of the position and electronic character of these substituents on the formation of the oxazole ring.
TL;DR: In this article, an efficient and generalized photochemical methodology for the preparation of fluorinated quinazolin-4-ones is described, where the starting substrate is derived from 5-polyfluoro-3-phenyl(methyl)-1,2,4-oxadiazoles.
Abstract: An efficient and generalized photochemical methodology for the preparation of fluorinated quinazolin-4-ones is described. Depending on the starting substrate, quinazolin-4-ones bearing a perfluoroalkyl- or perfluoroarylsubstituent in position 2 or fluorine atoms on any positions of the benzo-fused moiety can easily be obtained. 5-Aryl-3-perfluoroalkylpentafluorophenyl- or 5-polyfluoroaryl-3-phenyl(methyl)-1,2,4-oxadiazoles, respectively, can be considered as ideal precursors that can be transformed into the target quinazolin-4-ones by irradiation in the presence of triethylamine (TEA) (at λ = 313 nm) or pyrene (at X = 365 nm) in dry methanol or acetonitrile as solvent. Some mechanistic considerations confirm the involvement of a photoinduced electron transfer process.
TL;DR: In this paper, the synthesis of natural pseurotins A and F 2 (8-Odemethylpseurotin A) and structurally related azaspirene (3), each possessing a novel heterospirocyclic system, i.e., 1-oxa-7-azaspiro[4.4]non-2-ene-4,6-dione skeleton, have been accomplished starting from D-glucose.
Abstract: Total syntheses of natural pseurotins A (1) and F 2 (8-Odemethylpseurotin A) (2) and structurally related azaspirene (3), each possessing a novel heterospirocyclic system, i.e., 1-oxa-7-azaspiro[4.4]non-2-ene-4,6-dione skeleton, have been accomplished starting from D-glucose.