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Seven-membered Ring (seven-membered + ring)
Selected AbstractsDihydroazulene Photoswitches: The First Synthetic Protocol for Functionalizing the Seven-Membered RingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2009Michael Åxman Petersen Abstract The first synthetic protocol for functionalizing the dihydroazulene (DHA) photoswitch in its seven-membered ring has been developed. This protocol is based on regioselective bromination, followed by regioselective elimination of HBr, and finally a palladium-catalyzed cross-coupling reaction with a terminal alkyne. The position of functionalization (C-7) was confirmed by X-ray crystal structure analysis. Light-induced ring opening of this compound to its vinylheptafulvene (VHF) isomer followed by thermal ring closure provides a mixture of two DHA regioisomers in a ratio that depends on the wavelength of irradiation and solvent polarity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Further Studies on the Synthesis of meso -Tetraarylazuliporphyrins under Lindsey,Rothemund Reaction Conditions and Their Conversion into BenzocarbaporphyrinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2003Timothy D. Lash Abstract Azulene has been shown to react with pyrrole and a series of aromatic aldehydes in the presence of boron trifluoride etherate to give meso -tetraarylazuliporphyrins 6. Good yields of azuliporphyrins were obtained for benzaldehyde, 4-chlorobenzaldehyde, 4-bromobenzaldehyde, and 4-iodobenzaldehyde, and under dilute conditions p -tolualdehyde gave respectable yields. In each case, substantial amounts of meso -tetraarylporphyrins were also formed and a minor fraction of carbaporphyrin by-products could be detected, but otherwise no other macrocyclic products could be identified. 4-Nitrobenzaldehyde gave relatively poor yields of the corresponding azuliporphyrin, while p -anisaldehyde only gave trace amounts of product. Pentafluorobenzaldehyde gave variable results, although in this case a large number of additional by-products were identified including N -fused pentaphyrin, hexaphyrin, and higher order porphyrinoids, but no expanded azulene-containing macrocycles could be detected. Azuliporphyrins undergo reversible nucleophilic substitution on the seven-membered ring with pyrrolidine, benzenethiol, hydrazine, or benzylamine to give carbaporphyrin adducts. This property appears to facilitate an oxidative ring contraction of azuliporphyrins 6 with tert -butyl hydroperoxide in the presence of potassium hydroxide to produce mixtures of benzocarbaporphyrins 19 and 20. Tetraaryl-benzocarbaporphyrins exhibit slightly reduced diatropic ring currents compared to their meso -unsubstituted counterparts, although their UV/Vis spectra are very porphyrin-like and exhibit strong Soret bands near 450 nm. The benzocarbaporphyrins undergo reversible protonation to give monocationic and dicationic species. The latter involves C -protonation to generate an internal CH2 within the macrocyclic cavity. X-ray crystallography of tetraphenylbenzocarbaporphyrin 19a confirms that the preferred tautomer has the two NHs on either side of the indene subunit, in agreement with previous theoretical and spectroscopic studies. In addition, the presence of phenyl substituents at the 5,20-positions was found to tilt the indene moiety substantially by 27.4(1)° relative to the [18]annulene substructure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Structure,Activity Relationship in the Domain of Odorants Having Marine NotesHELVETICA CHIMICA ACTA, Issue 7 2007Jean-Marc Gaudin Abstract We synthesized or re-synthesized a large series of 2H -1,5-benzodioxepin-3(4H)-ones 9 (Scheme,1), 4,5-dihydro-1-benzoxepin-3(2H)-ones 10 (Schemes 3 and 4) and 5,6,8,9-tetrahydro-7H -benzocyclohepten-7-ones 11 (Schemes 5 and 6), since the lead compound for the olfactory note of perfumes based on marine accords is a well-known benzodioxepinone named Calone 1951® (9b). We meticulously described the odor profile of each synthesized compound and discussed relevant structure,odor relationships (Tables,1,3). In particular, we revealed a correlation between the conformation of the seven-membered ring and the activities of these compounds (Table,4 and Fig.,3). We also clarified the effect of the position and the size of the alkyl substituent at the aromatic ring. [source] Theoretical study of carbon atom scrambling in benzenium ions with ethyl or isopropyl groupsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2006Bjørnar Arstad Abstract Carbon atom scrambling is observed in benzenium ions in the mass spectrometer and in isotopic labeling experiments in the methanol-to-hydrocarbons reaction over acidic zeolites. We have shown plausible scrambling mechanisms in ethyl- and isopropylbenzenium ions and various intramolecular interconversion reactions that may take place in alkylbenzenium ions. Quantum chemical Density Functional Theory (DFT) modeling at the B3LYP/cc-pVTZ//B3LYP/6-311G(d,p) level of theory has been carried out to investigate carbon atom scrambling reactions in ethyl- and isopropyl(methyl)benzenium ions. A total of 85 stationary points have been calculated (48 minima and 37 transition states). The carbon atom scrambling reactions start with an initial ring expansion of the benzenium ions to a seven-membered ring. The seven-membered ring may rearrange and at a later stage re-contract to the original benzenium species, albeit with some atoms interchanged, i.e. there has been atom scrambling. Copyright © 2005 John Wiley & Sons, Ltd. [source] Gas-phase fragmentation study of novel synthetic 1,5-benzodiazepine derivatives using electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2008Mohamed Rida The fragmentation patterns of a series of three novel synthesized 3-hydroxy-4-phenyl-tetrahydro-1,5-benzodiazepin-2-ones (1,3), possessing the same backbone structure, were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) techniques. A simple methodology, based on the use of ESI (positive ion mode) and by increasing the declustering potential in the atmospheric pressure/vacuum interface, collision-induced dissociation (CID), was used to enhance the formation of the fragment ions. In general, the novel synthetic 1,5-benzodiazepine derivatives afforded, in the gas phase, both protonated and sodiated molecules. This led to the confirmation of the molecular masses and chemical structures of the studied compounds. Exact accurate masses were measured using a high-resolution ESI-quadrupole orthogonal time-of-flight (QqToF)-MS/MS hybrid mass spectrometer instrument. The breakdown routes of the protonated molecules were rationalized by conducting low-energy collision CID-MS/MS analyses (product ion- and precursor ion scans) using a conventional quadrupole-hexapole-quadrupole (QhQ) tandem mass spectrometer. All the observed major fragmentations for the 1,5-benzodiazepines occurred in the saturated seven-membered ring containing the nitrogen atoms. These formed a multitude of product ions by different breakdown routes. All the major fragmentations involved cleavages of the N -1,C -2 andC -3,C -4 bonds. These occurred with concomitant eliminations of glyoxal, benzene and ethyl formate, forming the product ion at m/z 119, which was observed in all the studied compounds. In addition, an unique simultaneous CID-MS/MS fragmentation was noticed for the 1,5-benzodiazepines 1 and 3, which occurred by a pathway dictated by the substituent located on the N -1-position. It was evident that the aromatic ring portion of the 1,5-benzodiazepines was resistant to CID-MS/MS fragmentation. Re-confirmation of the various geneses of the product ions was achieved by conducting a series of precursor ion scans. ESI-MS and CID-MS/MS analyses have thus proven to be a specific and very sensitive method for the structural identification of these novel 1,5-benzodiazepine derivatives. Copyright © 2008 John Wiley & Sons, Ltd. [source] 2-Amino-4-(piperidin-1-yl)-11H -pyrimido[4,5- b][1,5]benzodiazepin-6-ium chloride monohydrate and 2-amino-4-[methyl(2-methylphenyl)amino]-11H -pyrimido[4,5- b][1,5]benzodiazepin-6-ium chloride,benzene-1,2-diamine (1/1): complex sheets generated by multiple hydrogen bondsACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Jairo Quiroga In each of 2-amino-4-(piperidin-1-yl)-11H -pyrimido[4,5- b][1,5]benzodiazepin-6-ium chloride monohydrate, C16H19N6+·Cl,·H2O, (I), and 2-amino-4-[methyl(2-methylphenyl)amino]-11H -pyrimido[4,5- b][1,5]benzodiazepin-6-ium chloride,benzene-1,2-diamine (1/1), C19H19N6+·Cl,·C6H8N2, (II), the seven-membered ring in the cation adopts a boat conformation. The pyrimidine ring in (II) adopts a twist-boat conformation, but the corresponding ring in (I) is essentially planar. The amino groups of the benzene-1,2-diamine component of (II) are both pyramidal. The independent components of (I) are linked into complex sheets by a combination of N,H...O, N,H...N, N,H...Cl and O,H...Cl hydrogen bonds. In the crystal structure of (II), one N,H...N hydrogen bond and six independent N,H...Cl hydrogen bonds combine to link the components into complex sheets. [source] rac -5-Diphenylacetyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine and rac -5-formyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepineACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Thanikasalam Kanagasabapathy rac -5-Diphenylacetyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine, C26H27NOS, (I), and rac -5-formyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine, C13H17NOS, (II), are both characterized by a planar configuration around the heterocyclic N atom. In contrast with the chair conformation of the parent benzothiazepine, which has no substituents at the heterocyclic N atom, the seven-membered ring adopts a boat conformation in (I) and a conformation intermediate between boat and twist-boat in (II). The molecules lack a symmetry plane, indicating distortions from the perfect boat or twist-boat conformations. The supramolecular architectures are significantly different, depending in (I) on C,H...O interactions and intermolecular S...S contacts, and in (II) on a single aromatic ,,, stacking interaction. [source] (P,M)-1,2,3,9,10,11-Hexamethoxy-5,7-dihydrodibenz[c,e]oxepine and (P,M)-1,11-dimethyl-5,5,7,7-tetraphenyl-5,7-dihydrodibenz[c,e]oxepineACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004Anthony Linden The title compounds, C20H24O7 and C40H32O, respectively, are racemic oxepines, the molecules of which contain a chiral axis. Both molecules possess crystallographic C2 symmetry and the seven-membered ring adopts a twisted-boat conformation. [source] Diéthyl 10-chloro-7-méthyl-6-oxo-11b-phényl-2,3,5,6,7,11b-héxahydrooxazolino[3,2- d][1,4]benzodiazépine-2,3-carboxylateACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2000R. Benelbaghdadi The structure of the title compound, C24H25ClN2O6, has been established and the central seven-membered ring is fused to chlorobenzo and oxazolino rings to form the core of the molecule. [source] Bonding in Tropolone, 2-Aminotropone, and Aminotroponimine: No Evidence of Resonance-Assisted Hydrogen-Bond EffectsCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2008Pablo Sanz Dr. Abstract The properties of the intramolecular hydrogen bond (IMHB) in tropolone, aminotropone, and aminotroponimine have been compared with those in the corresponding saturated analogues at the B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d,p) level of theory. In general, all those compounds in which the seven-membered ring is unsaturated exhibit a stronger IMHB than their saturated counterparts. Nevertheless, this enhanced strength is not primarily due to resonance-assisted hydrogen-bond effects, but to the much higher intrinsic basicity and acidity of the hydrogen-bond acceptor and donor groups, respectively, in the unsaturated compounds. These acidity and basicity enhancements have a double origin: 1),the unsaturated nature of the moiety to which the hydrogen-bond donor and acceptor are attached and 2),the cyclic nature of the compounds under scrutiny. As has been found for hydroxymethylene and aminomethylene cyclobutanones, and cyclobutenones and their nitrogen-containing analogues, the IMHB strength follows the [donor, acceptor] trend: [OH, CNH]>[OH, CO]>[NH2, CNH]>[NH2, CO] and fulfills a Steiner,Limbach correlation similar to that followed by intermolecular hydrogen bonds. [source] Bisamides Derived from Azulene-1,3- and -5,7-dicarboxylic Acids as New Building Blocks for Anion ReceptorsCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2008Tomasz Zieli, ski Dr. Abstract Bisamides based on the azulene moiety were investigated as building blocks for anion receptors. In the course of these studies, derivatives of azulene-1,3- and -5,7-dicarboxylic acid were synthesized and thoroughly characterized. The anion affinities of the derivatives based on functionalization in the five-membered ring and in the seven-membered ring were determined by 1H,NMR titration. The structural analysis of these building blocks was performed by X-ray diffractometry, molecular modelling and 2D NMR spectroscopy. The five-membered ring derivatives are easy to obtain, offer a binding site preorganized in the syn,syn conformation and bind anions with a strength similar to those of pyrrole-based analogues. There is also strong evidence for aromatic CH,,,anion interactions. The ligands substituted at the 5- and 7-positions offer a binding cleft with an uncommon geometry that originates from the seven-membered ring and seems to be complementary to the chloride anion. [source] Four 2-amino-6-aryl-4-methoxy-11H -pyrimido[4,5- b][1,4]benzodiazepines: similar molecular structures but different crystal structuresACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2008Ricaurte Rodríguez 2-Amino-4-methoxy-6-phenyl-11H -pyrimido[4,5- b][1,4]benzodiazepine, C18H15N5O, (I), and its 6-(2-fluorophenyl)-, 6-(3-nitrophenyl)- and 6-(4-methoxyphenyl)- analogues, viz. C18H14FN5O, (II), C18H14N6O3, (III), and C19H17N5O2, (IV), respectively, all adopt molecular conformations which are almost identical, containing boat-shaped seven-membered rings. In each structure, paired N,H...N hydrogen bonds link the molecules into centrosymmetric dimers. In each of (I),(III), the dimers are further linked, forming a different three-dimensional framework in each case, while in compound (IV) the dimers are linked into sheets. The significance of this study lies in the observation of different crystal structures in four compounds whose molecular structures are very similar. [source] A comparison of 2,7-dihydro-2,2,7,7-tetramethyl-3,6-diphenyl-1,4,5-thiadiazepine and the corresponding 1,1-dioxideACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2001Eric Cuthbertson The structures of the highly substituted title heterocycles, C20H22N2S and C20H22N2O2S, have been determined at 123,(1),K. Both molecules possess exact C2 symmetry and the seven-membered rings have very similar twist-boat conformations. The magnitudes of the C,S,C bond angles, 107.13,(6) and 108.27,(7)°, respectively, are influenced significantly by the four substituent methyl groups on the seven-membered rings. [source] 1,4,4-Trimethyl-9-phenyl-8-oxa-9-azabicyclo[3.2.2]non-6-en-2-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2000Silvia Russi The structure of the adduct of eucarvone with nitrosobenzene, C16H19NO2, is reported. The [3.2.2] bicyclic system corresponds to two seven-membered rings in boat and distorted chair conformations and a six-membered ring that adopts a distorted boat conformation. No conjugation is observed between the phenyl group and the N,O system. The packing is directed mainly by a C,O hydrogen bond, C,H,O-(1,,,x, ,y, z) and by intermolecular C,H,, interactions. [source] | ||||||||||