Home About us Contact
|
Home About us Contact | ||
|
|
||
Heterocyclic Ring (heterocyclic + ring)
Kinds of Heterocyclic Ring Terms modified by Heterocyclic Ring Selected AbstractsChemInform Abstract: Synthesis of Homoproline Analogues Containing Heterocyclic Rings and Their Activity as Organocatalysts for Michael Reaction.CHEMINFORM, Issue 38 2009Efrosini Barbayianni Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Zeolite-Catalyzed Simple Synthesis of Different Heterocyclic Rings.CHEMINFORM, Issue 4 2005Part 2. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of some novel bis(hetaryl)azo disperse dyes and investigation of their absorption spectraHETEROATOM CHEMISTRY, Issue 6 2007Zeynel Sefero 3-Amino-2-cyano-4,6-disubstituted-thieno{2,3-b}pyridines and 3-aminopyridine were diazotized and coupled with 2-phenylindole, 2-methylindole, and 1-methyl-2-phenylindole, respectively. These dyes were characterized by UV-Visible, FT-IR, 1H NMR, and mass spectroscopic techniques. Solvent effects on the visible absorption spectra of the dyes were evaluated. The color of the dyes is discussed with respect to the nature of the heterocyclic ring and substituent present therein. In addition, effects of temperature, concentration, as well as acid and base on the visible absorption maxima of the dyes are reported. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:622,630, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20361 [source] Theoretical studies on thiabenzene and its fused derivatives: DFT and ab initio computationsHETEROATOM CHEMISTRY, Issue 5 2006M. Z. Kassaee The molecular structures of thiabenzene (1), 1-thianaphthalene (2), 2-thianaphthalene (3), and 9-thiaanthracene (4) are studied using HF and DFT methods with 6-31+G* basis set. The nonplanar boat conformers of 1,4, with 6,-electrons in their heterocyclic ring, appear more stable than the corresponding planar conformers with 8,-electrons in the ring. This study focuses on the stability, the ylide character, the inversion barrier energy of sulfur atoms, and the conformational flexibility of the ring in 1,4. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:376,381, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20214 [source] Bis-8-hydroxyquinoline and bis-8-hydroxyquinaldine N -substituted amines: A single methyl group structural difference between the two heterocycles, which modulates the antiproliferative effectsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2010Sébastien Madonna The synthesis of a series of bis-8-hydroxyquinoline- and bis-8-hydroxyquinaldine-substituted N -benzyl or thiophenyl amines and their corresponding bis-8-hydroxyquinoline is reported. In vitro growth inhibitory effects of both series have been evaluated. It has been observed that analogs from the bis-8-hydroxyquinoline series exert nanomolar range activity, whereas the antiproliferative activity of the corresponding analogs from the bis-8-hydroxyquinaldine series was found to be drastically lower. Molecular docking and chemical,physical properties account for these observed growth inhibitory differences between the two series of analogs, which differ only by the presence of a methyl group at the 2 position of the heterocyclic ring. J. Heterocyclic Chem., (2010). [source] Conformational exchange in pimonidazole,a hypoxia markerMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2007Cristina Gabellieri Abstract Pimonidazole is one of a series of nitroimidazole compounds that is widely used as a marker for qualitative and quantitative assessment of tumour hypoxia. We have observed a novel dynamic conformational exchange process in this molecule in aqueous solution. By a combination of 1H, 13C, two-dimensional 1H,1H EXchange SpectroscopY (EXSY) and spectral simulation, we unambiguously attribute the conformational exchange process to flipping of the six-membered heterocyclic ring. Copyright © 2007 John Wiley & Sons, Ltd. [source] Degradation of anilinopyrimidine fungicides photoinduced by iron(III),polycarboxylate complexesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2006Laura Anfossi Abstract The photoinduced degradation of three anilinopyrimidine fungicides (cyprodinil, pyrimethanil and mepanipyrim) by Fe(III),polycarboxylate complexes in aqueous solution was investigated. A photochemical redox reaction of Fe(III) complexes of oxalate and citrate occurs during irradiation (simulating sunlight) and is an important source of Fe(II) and a series of oxidants such as H2O2 and O radicals. The mechanism involves the formation of polycarboxylate radicals and/or carbon-centred radicals derived from decarboxylation, whereas the contribution of Fe(OH)2+ to O radical formation is negligible. The attack of O radicals on the fungicide molecules produces numerous photodegradation products, which were identified by means of LC-ES-MS and turned out to be mono- or dihydroxylated derivatives of the active ingredients, except for 2-amino-4,6-dimethylpyrimidine, which is only formed by pyrimethanil. The half-lives of the active ingredients, when submitted to irradiation in the presence of iron(III),polycarboxylate complexes, were estimated to vary between 28 and 79 min (photodegradation rates in the same conditions: mepanipyrim > cyprodinil > pyrimethanil), and photodegradation is slower in citrate than in oxalate solutions. Photoproducts and their kinetics of formation are very similar for the three fungicides. The OH substitution involves the aromatic and the heterocyclic ring and the nitrogen bridge between the two rings, except for mepanipyrim when the hydroxylation also involves the propynylic side chain. Copyright © 2006 Society of Chemical Industry [source] Influence of substituent groups at the 3-position on the mass spectral fragmentation pathways of cephalosporinsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010Jin Li The structural fragment ions of nine cephalosporins were studied by electrospray ionization quadrapole trap mass spectrometry (Q-Trap MSn) in positive mode. The influence of substituent groups in the 3-position on fragmentation pathway B, an ,-cleavage between the C7C8 single bond, coupled with a [2,4]-trans-Diels-Alder cleavage simultaneously within the six-membered heterocyclic ring, was also investigated. It was found that when the substituent groups were methyl, chloride, vinyl, or propenyl, fragmentations belonging to pathway B were detected; however, when the substituents were heteroatoms such as O, N, or S, pathway B fragmentation was not detected. This suggested that the [M,R3]+ ion, which was produced by the bond cleavage within the substituent group at the 3-position, had a key influence on fragmentation pathway B. This could be attributed to the strong electronegativity of the heteroatoms (O, N, S) that favors the production of the [M,R3]+ ion. Moreover, having the positive charge of the [M,R3]+ ion localized on the nitrogen atom in the 1-position changed the electron density distribution of the heterocyclic structure, which prohibits a [2,4]-reverse-Diels-Alder fragmentation and as a result fragmentation pathway B could not occur. The influence of the substituent group in the 3-position was determined by the intensity ratio (e/d) of ions produced by fragmentation pathway A, a [2,2]-trans-Diels-Alder cleavage within the quaternary lactam ring, including the breaking of the amide bond and the C6C7 single bond (ion d), and fragmentation pathway B (ion e). The results indicate that the electronegativity of the substituent group was a key influencing factor of pathway B fragmentation intensity, because the intensity ratio (e/d) is higher for a chlorine atom, a vinyl, or a propenyl group than that of a methyl group. This study provided some theoretical basis for the identification of cephalosporin antibiotics and structural analysis of related substances in drugs. Copyright © 2010 John Wiley & Sons, Ltd. [source] 10-Benzyl-4-oxo-2,3,4,10-tetrahydropyrimido[4,5- b]quinolin-2-iminium chloride sesquihydrate: a polarized electronic structure within a complex hydrogen-bonded sheet structureACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Jorge Trilleras In the title compound, C18H15N4O+·Cl,·1.5H2O, one water site is fully ordered with unit occupancy while the other, which lies close to an inversion centre in the space group C2/c, has only 0.5 occupancy. The cation exhibits bond fixation in the fused carbocyclic ring and electronic polarization in the terminal heterocyclic ring. The components are linked into complex sheets by a combination of N,H...O, N,H...Cl, O,H...O, O,H...Cl and C,H...O hydrogen bonds. [source] Anomeric effect and hydrogen-bonded supramolecular motif in 5-(3-fluoro-4-methoxyphenyl)-1-[(3-fluoro-4-methoxyphenyl)aminomethyl]-1,3,5-triazinane-2-thioneACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Zhenfeng Zhang In the title compound, C18H20F2N4O2S, the triazinane-2-thione ring adopts an envelope conformation, the ring substituents lie on the same side of the mean plane of the heterocyclic ring and the exo lp,N,C,Ntriaz unit (lp is a lone pair and triaz is the triazinane ring) exhibits an antiperiplanar orientation, which is shown to be governed by strong anomeric effects. Molecules are linked into a complex three-dimensional framework by a combination of two N,H...S hydrogen bonds, three C,H...F hydrogen bonds and a ,,, stacking interaction. [source] Conformational and configurational disorder in 6-(3,4,5-trimethoxyphenyl)-6,7-dihydro-5H -1,3-dioxolo[4,5- g]quinolin-8(5H)-one and 6-(1,3-benzodioxol-5-yl)-6,7-dihydro-5H -1,3-dioxolo[4,5- g]quinolin-8-one: a hydrogen-bonded chain of rings and ,-stacked hydrogen-bonded chainsACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Paola Cuervo In 6-(3,4,5-trimethoxyphenyl)-6,7-dihydro-5H -1,3-dioxolo[4,5- g]quinolin-8(5H)-one, C19H19NO6, (I), the six-membered heterocyclic ring adopts a conformation intermediate between envelope and half-chair forms; it is disordered over two enantiomeric configurations, with occupancies of 0.879,(3) and 0.121,(3), leading to positional disorder of the 3,4,5-trimethoxyphenyl unit. In 6-(1,3-benzodioxol-5-yl)-6,7-dihydro-5H -1,3-dioxolo[4,5- g]quinolin-8-one, C17H13NO5, (II), the molecules are similarly disordered, with occupancies of 0.866,(4) and 0.134,(4). The molecules in (I) are linked by one three-centre N,H...(O)2 hydrogen bond and one two-centre C,H...O hydrogen bond to form a complex chain of rings whose formation is reinforced by two independent aromatic ,,, stacking interactions. In (II), a single N,H...O hydrogen bond links the molecules into a simple chain, and pairs of chains are linked by a single aromatic ,,, stacking interaction. [source] The influence of sulfur substituents on the molecular geometry and packing of thio derivatives of N -methylphenobarbitalACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Alicja Janik The room-temperature crystal structures of four new thio derivatives of N -methylphenobarbital [systematic name: 5-ethyl-1-methyl-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trione], C13H14N2O3, are compared with the structure of the parent compound. The sulfur substituents in N -methyl-2-thiophenobarbital [5-ethyl-1-methyl-5-phenyl-2-thioxo-1,2-dihydropyrimidine-4,6(3H,5H)-dione], C13H14N2O2S, N -methyl-4-thiophenobarbital [5-ethyl-1-methyl-5-phenyl-4-thioxo-3,4-dihydropyrimidine-2,6(1H,5H)-dione], C13H14N2O2S, and N -methyl-2,4,6-trithiophenobarbital [5-ethyl-1-methyl-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trithione], C13H14N2S3, preserve the heterocyclic ring puckering observed for N -methylphenobarbital (a half-chair conformation), whereas in N -methyl-2,4-dithiophenobarbital [5-ethyl-1-methyl-5-phenyl-2,4-dithioxo-1,2,3,4-tetrahydropyrimidine-6(5H)-one], C13H14N2OS2, significant flattening of the ring was detected. The number and positions of the sulfur substituents influence the packing and hydrogen-bonding patterns of the derivatives. In the cases of the 2-thio, 4-thio and 2,4,6-trithio derivatives, there is a preference for the formation of a ring motif of the R22(8) type, which is also a characteristic of N -methylphenobarbital, whereas a C(6) chain forms in the 2,4-dithio derivative. The preferences for hydrogen-bond formation, which follow the sequence of acceptor position 4 > 2 > 6, confirm the differences in the nucleophilic properties of the C atoms of the heterocyclic ring and are consistent with the course of N -methylphenobarbital thionation reactions. [source] Low-temperature study of 3-acetylindole at 110,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008Barbara Hachu The title compound, C10H9NO, contains an acetyl group that is nearly coplanar with the indole ring system, with an angle between the planes of the heterocyclic ring and the acetyl group of 1.75,(17)°. The planes of the benzene and pyrrole rings in the indole system make a dihedral angle of 2.05,(11)°. Each molecule in the unit cell is linked through N,H...O hydrogen bonds to two other molecules, forming hydrogen-bonded chains in the [101] direction with graph set C(6). The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds in this structure, as well as in the comparison drawn between the molecular structure of the title compound and those of several other indole derivatives possessing a 3-carbonyl group. The correlation between the IR spectrum of this compound and the structural data is also discussed. [source] 5-Acetyl-2-amino-6-methyl-4-phenyl-4H -pyran-3-carbonitrile and 2-amino-5-benzoyl-6-methyl-4-phenyl-4H -pyran-3-carbonitrile acetonitrile solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2006Vladimir N. Nesterov The syntheses, X-ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C15H14N2O2, (II), and C20H16N2O2·C2H3N, (III), respectively. In both molecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo-axial phenyl substituent and the flat part of the pyran ring are 92.7,(1) and 93.2,(1)° in (II) and (III), respectively. In the crystal structure of (II), intermolecular N,H,N and N,H,O hydrogen bonds link the molecules into a sheet along the (103) plane, while in (III), they link the molecules into ribbons along the a axis. [source] 18-Deoxy-13,,14-dihydrolycoctam: the lycoctamone rearrangement confirmedACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2006Michael Benn The structure of the title compound, C23H35NO4, contains a unique pentacyclic ring system wherein one cyclohexyl ring adopts a chair conformation, two cyclohexyl rings are in boat conformations, and a six-membered heterocyclic ring and a cyclopentyl ring are in envelope conformations. The structures of the lycoctamones, ,,,-unsaturated aldehydes produced by acid-catalyzed degradation of lactams of lycoctonine-type alkaloids, previously deduced from the results of extensive chemical investigations have been proven to be correct by the determination of the crystal structure of this compound. [source] An oximino tautomer of 1- n -decyl-4-hydroxyimino-3-methyl-1H -pyrazol-5(4H)-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2006Ricardo Baggio The title compound, C14H25N3O2, consists of a five-membered heterocyclic ring to which a pendant decyl group is attached. The oximino tautomeric character of the molecule is clearly defined by the distribution of well defined double bonds in the heterocycle region (one C=O and two C=N). The most conspicuous packing interaction is the strong intermolecular hydrogen bond linking the oximino OH group and the carbonyl O atom to define broad planar hydrophilic strips running along the unique b axis. The alkyl chains adopt a fully extended conformation and lie almost at right angles to these one-dimensional structures, defining their hydrophobic counterpart. [source] 2-Amino-4-(1-naphthyl)-5-oxo-5,6,7,8-tetrahydro-4H -chromene-3-carbonitrile and 2-amino-7,7-dimethyl-4-(1-naphthyl)-5-oxo-5,6,7,8-tetrahydro-4H -chromene-3-carbonitrileACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2004Vladimir N. Nesterov Syntheses and X-ray structural investigations have been carried out for the two title compounds, C20H16N2O2, (IIIa), and C22H20N2O2, (IIIb). In (IIIa), the heterocyclic ring adopts a sofa conformation, while in (IIIb), the ring has a flattened boat conformation. In both molecules, the fused cyclohexenone ring adopts a sofa conformation. The dihedral angles between these two flat fragments are 3.5,(2) and 17.5,(2)° in (IIIa) and (IIIb), respectively. The dihedral angles between the pseudo-axial naphthalene substituents and the planes of the pyran rings are 90.9,(1) and 96.7,(1)°, respectively. In the crystal structure of (IIIa), intermolecular N,H,N and N,H,O hydrogen bonds link the molecules into infinite tapes along the b axis, while molecules of (IIIb) form centrosymmetric dimers via N,H,N hydrogen bonds, with only one H atom of the NH2 donor group taking part in hydrogen bonding. [source] 3,,4,-Bis(4-chlorophenyl)spiro[chroman-3,5,(4,H)-isoxazol]-4-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2001A. Abdul Ajees The title compound, C23H15Cl2NO3, crystallizes with two independent molecules in the asymmetric unit. The chromanone moiety consists of a benzene ring fused with a six-membered heterocyclic ring which adopts a sofa conformation. The five-membered spiroisoxazoline ring is in an envelope conformation. The p -chlorophenyl rings bridged by the five-membered ring are nearly perpendicular to each other. The chromanone moiety of one molecule packs into the cavity formed by the p -chlorophenyl rings of a second molecule through the formation of C,H,, interactions. The structure is stabilized by weak C,H,O, C,H,Cl and C,H,, interactions. [source] Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of PiperidinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2006Mercedes Amat Prof. Abstract A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2- a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiral auxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols with racemic or prochiral ,-oxo (di)acid derivatives in highly stereoselective processes involving dynamic kinetic resolution and/or desymmetrization of diastereotopic or enantiotopic ester groups. Se describe un procedimiento directo para la síntesis enantioselectiva de piperidinas polisustituidas. Consiste en la generación directa de oxazolo[3,2-a]piperidonas quirales no racémicas que ya incorporan sustituyentes carbonados en las diferentes posiciones del heterociclo, y en la posterior eliminación del auxiliar quiral. La etapa clave es una reacción de ciclocondensación entre el (R)-fenilglicinol, u otros amino alcoholes quirales, con derivados de , -oxo ácidos racémicos o proquirales, en procesos altamente estereoselectivos que implican una resolución cinética dinámica y/o la desimetrización de grupos diastereotópicos o enantiotópicos. [source] Zeolite-catalyzed simple synthesis of different heterocyclic rings, part 2,HETEROATOM CHEMISTRY, Issue 6 2004Adrienn Hegedüs A simple and environmentally friendly synthesis was developed for the preparation of 2-arylimidazoline derivatives and 2-arylbenzoxazole derivatives using a small pore size zeolite. The similar reaction was not applicable to the preparation of the sulfur-containing analogs cysteamine or 2-aminothiophenol, probably because of a disadvantageous reaction between the zeolite and the thio compound. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:428,431, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20036 [source] Pyrimido[4,5- c]pyridazine-5,7(6H, 8H)-diones: Marvelous substrates for study of nucleophilic substitution of hydrogenJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2005Alexander F. Pozharskii The data on nucleophilic substitution reactions of hydrogen in 6,8-dimethylpyrimido[4,5- c]pyridazine-5,7(6H,8H)-dione, its 3-chloride, N2 -oxide and some other derivatives are reviewed. All these compounds possess a remarkable ability to undergo not only simple functionalizations but also tandem and cascade transformations leading to annelation of various heterocyclic rings. [source] Synthesis and Biological Activity of Endomorphin-2 Analogs Incorporating Piperidine-2-, 3- or 4-Carboxylic Acids Instead of Proline in Position 2CHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2008Renata Staniszewska Novel endomorphin-2 (EM-2) analogs have been synthesized, incorporating unnatural amino acids with six-membered heterocyclic rings, such as piperidine-2-, 3- and 4-carboxylic acids (Pip, Nip and Inp, respectively) instead of Pro in position 2. [(R)-Nip2]EM-2 displayed an extremely high affinity for the ,-opioid receptor with IC50 = 0.04 ± 0.01 nm in comparison with IC50 = 0.69 ± 0.03 nm for EM-2. This analog was also very potent in the aequorin luminescence-based functional calcium assay and showed significantly enhanced stability in rat brain homogenate. [source] Identification, SAR Studies, and X-ray Co-crystallographic Analysis of a Novel Furanopyrimidine Aurora Kinase,A InhibitorCHEMMEDCHEM, Issue 2 2010Mohane Selvaraj Coumar Dr. Abstract Herein we reveal a simple method for the identification of novel Aurora kinase,A inhibitors through substructure searching of an in-house compound library to select compounds for testing. A hydrazone fragment conferring Aurora kinase activity and heterocyclic rings most frequently reported in kinase inhibitors were used as substructure queries to filter the in-house compound library collection prior to testing. Five new series of Aurora kinase inhibitors were identified through this strategy, with IC50 values ranging from ,300,nM to ,15,,M, by testing only 133 compounds from a database of ,125,000 compounds. Structure,activity relationship studies and X-ray co-crystallographic analysis of the most potent compound, a furanopyrimidine derivative with an IC50 value of 309,nM toward Aurora kinase,A, were carried out. The knowledge gained through these studies could help in the future design of potent Aurora kinase inhibitors. [source] | ||||||||||