- Highly stable dioxin-linked metallophthalocyanine covalent organic frameworks
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We report a series of highly stable metallophthalocyanine-based covalent organic frameworks (MPc-dx-COFs) linked by robust 1,4-dioxin bonds constructed through nucleophilic aromatic substitution (SNAr) reaction. The chemical structures and crystallinity of the COFs largely remain unchanged even after treating with boiling water (90 °C), concentrated acids (12 mol/L HCl) or bases (12 mol/L NaOH), oxidizing (30% H2O2) or reducing agents (1 mol/L NaBH4) for three days due to their stable M-Pc building blocks and resilient dioxin linkers. With metallated phthalocyanine active sites regularly arranged in the stable framework structures, MPc-dx-COFs can be directly used as efficient electrocatalysts for the oxygen reduction reaction (ORR) without pyrolysis treatment that has commonly been used in previous studies.
- Bodkin, Lauren,Canales Moya, Enrique,Holewinski, Adam,Huang, Shaofeng,Jin, Yinghua,Lei, Zepeng,Li, Patrick,Lucas, Francisco W. S.,Rong, Yicheng,Wesche, Aaron,Zhang, Wei
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- Supersnowflakes: Stepwise Self-Assembly and Dynamic Exchange of Rhombus Star-Shaped Supramolecules
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With the goal of increasing the complexity of metallo-supramolecules, two rhombus star-shaped supramolecular architectures, namely, supersnowflakes, were designed and assembled using multiple 2,2′:6′,2″-terpyridine (tpy) ligands in a stepwise manner. In the design of multicomponent self-assembly, ditopic and tritopic ligands were bridged through Ru(II) with strong coordination to form metal-organic ligands for the subsequent self-assembly with a hexatopic ligand and Zn(II). The combination of Ru(II)-organic ligands with high stability and Zn(II) ions with weak coordination played a key role in the self-assembly of giant heteroleptic supersnowflakes, which encompassed three types of tpy-based organic ligands and two metal ions. With such a stepwise strategy, the self-sorting of individual building blocks was prevented from forming the undesired assemblies, e.g., small macrocycles and coordination polymers. Furthermore, the intra- and intermolecular dynamic exchange study of two supersnowflakes by NMR and mass spectrometry revealed the remarkable stability of these giant supramolecular complexes.
- Zhang, Zhe,Wang, Heng,Wang, Xu,Li, Yiming,Song, Bo,Bolarinwa, Olapeju,Reese, R. Alexander,Zhang, Tong,Wang, Xu-Qing,Cai, Jianfeng,Xu, Bingqian,Wang, Ming,Liu, Changlin,Yang, Hai-Bo,Li, Xiaopeng
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- Efficient green procedures for the preparation of novel tetraalkynyl-substituted phthalocyanines
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This work provides a successful, easy and efficient process for the preparation of metal-free 2(3),9(10),16(17),23(24)-octamethoxyphthalocyanine, [(OMe)8PcH2] (2), and its metal complexes [(OMe)8PcM] (3-11) (M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) by using green energy techniques such as exposure to UV-irradiation as well as microwave irradiation. Two different routes have been used, which involve modifications to that reported in the literature. The results suggest that these techniques drastically reduce the reaction time of metallophthalocyanine [(OMe)8PcM] (3-11) formation from 5-96 h to 5-11 min. The prepared octamethoxyphthalocyanines [(OMe)8PcM] (2-4) (M = H2, Zn, Cu) are used as key materials to synthesize the corresponding novel tetraalkynyl-substituted phthalocyanines 15-17.
- Youssef, Tamer Ezzat
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- Synthesis and crystal structure of tris(2,3-triphenylenedioxy) cyclotriphosphazene: A new clathration system
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A new host compound TTPP (tris(2,3-triphenylenedioxy)cyclotriphosphazene), which is able to form a porous network, has been synthesized in five steps. When it crystallizes as a single component, TTPP exhibits a crystal structure with a monoclinic unit cell, the space group P21/c (no. 14) and unit cell dimensions of a = 14.909(2) A, b = 31.013(4) A, c = 9.074(1) A, β = 102.12(1)°. Co-crystallization of TTPP with 1,2,4-trichlorobenzene forms an inclusion crystal having a triclinic unit cell with a P1 space group (no. 2) and unit cell dimensions of a = 8.769(2) A, b = 15.024(2) A, c = 21.216(2) A, α = 94.82(0)°, β = 99.98(0)°, γ = 98.23(1). The guest lies in two kinds of channel-like cavities with dimensions of 6.1 × 8.4 A2 and 10.7 × 12.4 A2 respectively. This represents the biggest porous network built up by spirocyclotriphosphazene derivatives to date.
- Reynes, Mathias,Dautel, Olivier J.,Virieux, David,Flot, David,Moreau, Joel J. E.
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- Tetraphenyl ethylene terpyridine organic ligand compound and preparation method thereof Coordination supermolecule and preparation and application thereof (by machine translation)
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The invention belongs to the technical field of supramolecular materials, and particularly discloses a tetraphenyl ethylene terpyridine organic ligand compound as well as preparation and application thereof. The supramolecular has good fluorescence performance. (by machine translation)
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Paragraph 0049; 0056; 0057; 0089; 0090
(2020/12/15)
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- Synthesis of Metallopolymers and Direct Visualization of the Single Polymer Chain
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During the past few decades, the study of the single polymer chain has attracted considerable attention with the goal of exploring the structure-property relationship of polymers. It still, however, remains challenging due to the variability and low atomic resolution of the amorphous single polymer chain. Here, we demonstrated a new strategy to visualize the single metallopolymer chain with a hexameric or trimeric supramolecule as a repeat unit, in which Ru(II) with strong coordination and Fe(II) with weak coordination were combined together in a stepwise manner. With the help of ultrahigh-vacuum, low-temperature scanning tunneling microscopy (UHV-LT-STM) and scanning tunneling spectroscopy (STS), we were able to directly visualize both Ru(II) and Fe(II), which act as staining reagents on the repeat units, thus providing detailed structural information for the single polymer chain. As such, the direct visualization of the single random polymer chain is realized to enhance the characterization of polymers at the single-molecule level.
- Hao, Xin-Qi,Hla, Saw-Wai,Li, Xiaohong,Li, Xiaopeng,Li, Yiming,Li, Zhikai,Lu, Shuai,Song, Bo,Tu, Yingfeng,Wang, Heng,Zhang, Yuan,Zhao, Yiming
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supporting information
p. 6196 - 6205
(2020/04/27)
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- Mixed er-NHC/phosphine Pd(ii) complexes and their catalytic activity in the Buchwald-Hartwig reaction under solvent-free conditions
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A series of novel (NHC)PdCl2-PR3 complexes were synthesized and fully characterized by 1H, 13C, 31P NMR and FT-IR spectroscopy. These complexes showed high catalytic activity toward solvent-free Buchwald-Hartwig amination. Both primary and secondary amines were efficiently utilized under the same reaction conditions. The solvent-free synthesis of valuable N-aryl carbazoles and similar N-heterocyclic systems was described.
- Ageshina, Alexandra A.,Sterligov, Grigorii K.,Rzhevskiy, Sergey A.,Topchiy, Maxim A.,Chesnokov, Gleb A.,Gribanov, Pavel S.,Nechaev, Mikhail S.,Asachenko, Andrey F.,Bermeshev, Maxim V.,Melnikova, Elizaveta K.
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supporting information
p. 3447 - 3452
(2019/04/30)
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- Palladium(II) octaalkoxy- and octaphenoxyphthalocyanines: Synthesis and evaluation as catalysts in the Sonogashira reaction
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Octaalkoxy- and octaphenoxysubstituted palladium phthalocyanines were used as a new family members of cross-coupling catalysts in the Sonogashira reaction. For the first time it was shown that terminal alkynes reacted mildly with p-substituted aryl bromides in gently conditions at room temperature under Pd and Cu-cocatalysis to give the corresponding phenylacetylenes. This protocol represents the use of palladium phthalocyanines as homogeneous catalysts in the Pd/Cu-promoted Sonogashira reaction.
- Platonova, Yana B.,Volov, Alexander N.,Tomilova, Larisa G.
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p. 222 - 227
(2019/04/17)
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- Diene-Transmissive Diels-Alder Sequences with Benzynes
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Diene-transmissive Diels-Alder (DTDA) sequences are extraordinarily powerful processes for the generation of fused bicyclic systems. Nonetheless, only stable dienophiles have previously been deployed. Herein we report DTDA sequences with a variety of substituted [3]dendralenes in the first study to deploy arynes as dienophiles. We demonstrate the one-flask generation of complex, aromatic-ring-containing, multicyclic systems of relevance to medicinal chemistry. These synthetic operations provide numerous successful examples of the otherwise challenging and rarely reported intermolecular Diels-Alder reaction of acyclic 1,3-butadienes with arynes, which is made possible due to the exalted reactivity of dendralenic dienes.
- George, Josemon,Ward, Jas S.,Sherburn, Michael S.
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supporting information
p. 7529 - 7533
(2019/10/02)
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- Dehydroxymethyl Bromination of Alkoxybenzyl Alcohols by Using a Hypervalent Iodine Reagent and Lithium Bromide
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We describe the dehydroxymethylbromination of alkoxybenzyl alcohol by using a hypervalent iodine reagent and lithium bromide in F 3 CCH 2 OH at room temperature. Selective monobromination or dibromination was possible by adjusting the molar ratios of hypervalent iodine reagent and lithium bromide.
- Shibata, Ayako,Kitamoto, Sara,Fujimura, Kazuma,Hirose, Yuuka,Hamamoto, Hiromi,Nakamura, Akira,Miki, Yasuyoshi,Maegawa, Tomohiro
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supporting information
p. 2275 - 2278
(2018/10/20)
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- 5,6-Bis(9-(2-decyltetradecyl)-6-fluoro-9H-carbazol-3-yl)naphtho[2,1-b:3,4-b']dithiophene as a Promising Donor Structure for D–A Conjugated Copolymers with a Narrow Bandgap
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A new carbazole-containing naphthodithiophene derivative—heteroaromatic compound 5,6- bis[9-(2-decyltetradecyl)-9H-carbazol-3-yl]naphtho[2,1-b:3,4-b']dithiophene (M1)—has been synthesized. The compound will be used by us as a weak donor structural block for fabricating narrow-bandgap D–A conjugated polymers. The composition and structure of M1 have been confirmed by elemental analysis data, IR spectroscopy, and 1H and 13C NMR. The synthesized compound has a low HOMO energy (–5.4 eV), which is favorable for a high open-circuit voltage. Monomer M1 can be used as a promising weak donor moiety in D–A conjugated polymers for solar photovoltaics.
- Keshtov,Kuklin,Konstantinov,Peregudov,Xie, Zhi-Yuan,Ostapov,Makhaeva,Khokhlov
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p. 213 - 219
(2018/11/21)
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- Looking for the Origin of Allosteric Cooperativity in Metallopolymers
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The basic concept of allosteric cooperativity used in biology, chemistry and physics states that any change in the intermolecular host-guest interactions operating in multisite receptors can be assigned to intersite interactions. Using lanthanide metals as guests and linear multi-tridentate linear oligomers of variable lengths and geometries as hosts, this work shows that the quantitative modeling of metal loadings requires the consideration of a novel phenomenon originating from solvation processes. It stepwise modulates the intrinsic affinity of each isolated site in multisite receptors, and this without resorting to allosteric cooperativity. An easy-to-handle additive model predicts a negative power law dependence of the intrinsic affinity on the length of the linear metallopolymer. Applied to lanthanidopolymers, the latter common analysis overestimates cooperativity factors by more than two orders of magnitude.
- Babel, Lucille,Hoang, Thi Nhu Y,Guénée, Laure,Besnard, Céline,Wesolowski, Tomasz A.,Humbert-Droz, Marie,Piguet, Claude
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supporting information
p. 8113 - 8123
(2016/06/13)
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- Synthesis and optical and electrochemical properties of 5,6-bis[9-(2-decyltetradecyl)-9H-carbazol-3-yl]naphtho[2,1-b:3,4-b’]dithiophene as a promising building block for photovoltaic applications
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A new carbazole-containing naphthodithiophene heteroaromatic compound, 5,6-bis[9-(2-decyltetradecyl)-9H-carbazol-3-yl]naphtho[2,1-b:3,4-b’]dithiophene (M1), was synthesized to be subsequently used as the weak donor structure for the construction of narrow bandgap D–A conjugated polymers in terms of the “weak donor–strong acceptor” concept. The composition and structure of M1 were confirmed by the data of elemental analysis and IR and 1H and 13C NMR spectroscopy. The optical and electrochemical characteristics of the product were measured. The compound M1 was shown to have low-lying HOMO (–5.57 eV), which is favorable for high open-circuit voltage and to be suitable as a promising weak donor moiety in the D–A conjugated polymer for photovoltaic applications.
- Keshtov,Kuklin,Godovskii, D. Yu.,Konstantinov,Krayushkin,Peregudov,Khokhlov
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- Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy to Assemble Them into Solid State Materials with a π-π Stacked Lamellar Structure
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Formation of π-π stacked lamellar structure is important for high performance organic semiconductor materials. We previously demonstrated that perfluoroalkylation of aromatics and heteroaromatics was one of the strategies to design organic crystalline materials with π-π stacked lamellar structures while improving air stability as a result of the strong electron withdrawing ability of perfluoroalkyl substituents. Square-planar transition metal complexes with large π-conjugated ligands are also an important category of semiconductor materials. We have perfluoroalkylated square-planar transition metal complexes, leading to the formation of a π-π stacked lamellar crystal packing motif in the solid state. Here we report six crystal structures of Pd and Pt complexes with bis-perfluorobutylated catechol ligand as one of the two ligands that bonds to the metal centers. This structural design possesses similar molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we have reported previously, again, demonstrating the steering power of the perfluoroalkyl substituents in engineering organic and organometallic solid state materials.
- Banikhaled, Mohammad O.,Becker, John D.,Koppang, Miles,Sun, Haoran
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p. 1869 - 1878
(2016/05/09)
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- Synthesis of Cyclopropanated 7-Azabenzonorbornadienes
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7-Azabenzonorbornadienes bearing various aryl or N-substituents were treated with diazomethane in the presence of palladium to afford desirable yields of cyclopropanated products (75-98%). The current approach suggests an efficient synthesis for CH2-cyclopropanated 7-azabenzonorbornadienes which lends promise to the development of new ring-opening preparations of biologically useful organic frameworks.
- Carlson, Emily,Tam, William
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p. 2449 - 2454
(2016/07/28)
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- Aerobic oxidative bromination of arenes using an ionic liquid as both the catalyst and the solvent
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A method for the bromination of alkoxy-substituted benzenes and naphthalenes was developed by using the residual oxygen in the reaction tube as the oxidant, and [Bmim]NO3 (1-butyl-3-methylimidazolium nitrate) ionic liquid as both the catalyst and the solvent. No other reagent apart from the ionic liquid and molecular bromine was used in the reactions, and basically all the bromine atoms in the bromine source were transferred to the bromination products, showing that the presented protocol is highly atom economic and practical.
- Ren, Yun-Lai,Wang, Binyu,Tian, Xin-Zhe,Zhao, Shuang,Wang, Jianji
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supporting information
p. 6452 - 6455
(2015/11/16)
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- Process for the synthesis of 3,4-dimethoxybicyclo[4.2.0]OCTA-1,3,5-triene-7-carbonitrile, and application in the synthesis of ivabradine and addition salts thereof with a pharmaceutically acceptable acid
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Process for the synthesis of the compound of formula (I): Application in the synthesis of ivabradine, addition salts thereof with a pharmaceutically acceptable acid and hydrates thereof.
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Page/Page column 5
(2014/10/29)
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- Practical and metal-free electrophilic aromatic halogenation by interhalogen compounds generated in situ from N-halosuccinimide and catalytic TMSCL
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Halomonochloride compounds (ClCl, BrCl, ICl) generated in situ from N-halosuccinimide and catalytic chlorotrimethylsilane (TMSCl, 0.1 equiv) can efficiently halogenate aromatic compounds to give halogenated products in good to excellent yields and selectivities. The reaction can be carried out at room temperature or at lower temperatures, requires only one hour, is practical to apply to a wide range of substrates, and provides a simple access to a variety of haloarene compounds. Georg Thieme Verlag Stuttgart New York.
- Maibunkaew, Tapanee,Thongsornkleeb, Charnsak,Tummatorn, Jumreang,Bunrit, Anon,Ruchirawat, Somsak
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supporting information
p. 1769 - 1775
(2014/08/05)
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- Pd-catalyzed direct arylation approach to the 6H-dibenzo[c,h]chromenes: Total synthesis of arnottin I
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An efficient synthesis of 6H-dibenzo[c,h]chromenes has been achieved from 2-bromobenzyl-α-naphthyl ethers via a Pd-catalyzed Intramolecular direct-arylation using easily available Pd(PPh3)4 or Pd(OAc)2/PPh3 at elevated temperature. The reaction affords biaryl-coupling products in good to excellent yields in 6-9 h (up to 94% yields). A tentative mechanism has been proposed to understand the reaction pathway. Applying the methodology, a straightforward and concise total synthesis of arnottin I has been demonstrated by converting the biaryl-coupling products to the 6H-benzo[d]naphtho[1,2-b]pyran-6-one using pyridinium chlorochromate (PCC) mediated oxidation.
- De, Subhadip,Chaudhuri, Saikat,Mishra, Sourabh,Mamtani, Himanshu,Bisai, Alakesh
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p. 1871 - 1884
(2014/01/17)
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- Mono-oxo-bis-dithioveratrol-molybdate - In Solution a Model for Arsenite Oxidase and in the Solid State a Coordination Polymer with Unprecedented Binding Motifs
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Mono-oxo-bis-dithioveratrol-molybdate was synthesized, structurally characterized, and investigated with respect to its oxo-transfer activity. The latter was compared with the activity of the analogous tungsten complex. The title complex is a structural model for molybdopterin bearing arsenite oxidase and both complexes catalyze oxo-transfer reactions successfully to 100 % conversion. With the dithioveratrol ligand the oxidation of triphenylphosphine proved to be faster for the tungsten complex, which is untypical. The solid-state structure of the molybdenum complex exhibits an unexpected and very unusual polymeric structural motif consisting of the complex anion mono-oxo-bis-dithioveratrol-molybdate, sodium cations, and methanol. Infinite double-decker strands are formed with sodium bridges between the ether functions of two ligands in one strand and the Mo=O moiety of the second strand. Copyright
- Doering, Alexander,Fischer, Christian,Schulzke, Carola
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p. 1552 - 1558
(2013/08/23)
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- METHOD FOR PRODUCING 2-BROMO-4,5-DIALKOXY BENZOIC ACID
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Provided is a method for effectively producing a 4,5-dialkoxy-2-hydroxybenzoic acid from an inexpensive raw material. A method for producing a 2-bromo-4,5-dialkoxybenzoic acid represented by the following formula (2): (wherein each of R1 and R2 represents a lower alkyl group), the method including causing a 3,4-dialkoxybenzoic acid represented by the following formula (1): (wherein R1 and R2 have the same meanings as defined above) to react with bromine in concentrated hydrochloric acid.
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Paragraph 0028; 0029; 0033
(2013/10/07)
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- Brominated methanes as photoresponsive molecular storage of elemental Br2
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The photochemical generation of elemental Br2 from brominated methanes is reported. Br2 was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br2 generation were photochemically controllable. Liquid CH 2Br2 can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br2, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br2 from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br2 that was generated by the photodecomposition of CH2Br2 retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br2 dissolved in CH 2Br2 that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH2Br2, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br2 from CH2Br2 was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br2 that was generated photochemically from CH 2Br2 was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br 2 from brominated methanes occurred upon photoirradiation under O2. The solutions that contained elemental Br2 were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright
- Kawakami, Kazumitsu,Tsuda, Akihiko
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p. 2240 - 2252
(2012/11/06)
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- Reactive conducting thiepin polymers
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(Chemical Equation Presented) We report the design and synthesis of annulated thiepins designed to undergo bent-to-planar transformation driven by aromatization under electrochemical control. Thiepins are conjugated seven-membered ring systems with a thioether in the macrocycle. We synthesized thermally stable thiepins that are electropolymerizable to give rise to thiepin-containing electroactive polymers. Extended thiepin systems undergo sulfur extrusion with oxidation, and this feature has utility in peroxide sensing. 2009 American Chemical Society.
- Song, Changsik,Swager, Timothy M.
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scheme or table
p. 999 - 1005
(2010/04/06)
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- Efficient halogenation of aromatic systems using N-halosuccinimides in ionic liquids
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A simple, rapid and highly regioselective green protocol has been developed for the halogenation of aromatic systems with N-halosuccinimides using room temperature ionic liquids (ILs) as novel and recyclable reaction media to produce the corresponding halogenated aromatic compounds in high to quantitative yields. N-Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times dramatically and improving the yields substantially.
- Yadav,Reddy,Reddy,Basak,Narsaiah
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- Pd catalyzed coupling of 1,2-dibromoarenes and anilines: Formation of N,N-diaryl-o-phenylenediamines
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1,2-Dibromoarenes were coupled with aniline derivatives to yield N,N-diaryl-o-phenylenediamines in moderate to good yield using a palladium/phosphine or palladium/carbene catalyst system. Under similar conditions, 1,2,4,5-tetrabromobenzene was coupled with aniline derivatives to produce the corresponding tetrasubstituted derivatives which are oxidized on workup to yield azophenines. The sequential reaction of two different anilines with 1-chloro-2-iodobenzene afforded mixed N,N-diaryl-o-phenylenediamines.
- Wenderski, Todd,Light, Kenneth M.,Ogrin, Doug,Bott, Simon G.,Harlan, C. Jeff
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p. 6851 - 6853
(2007/10/03)
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- Functionalizable polycyclic aromatics through oxidative cyclization of pendant thiophenes
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We present a general strategy for obtaining large sulfur-containing polycyclic aromatics from thienyl precursors through iron(Ill) chloride mediated oxidative cyclizations. By placing thienyl moieties in close proximity to adjacent arenes, we have directed the oxidized intermediates into controlled cyclization pathways, effectively suppressing polymer formation. Utilizing these cyclized compounds and their thienyl precursors, we have studied cyclization/polymerization pathways of polymers such as poly(2). The unsubstituted positions α to the sulfur atoms within these aromatic cores allowed for efficient halogenation and further functionalization. As a demonstration, we prepared a series of arylene-ethynylene polymers with varying degrees of chromophore aromatization and used them to probe the effects of synthetically imposed rigidity on polymer photophysical behavior. The symmetries and effective conjugation pathways within the monomers play a key role in determining photophysical properties. We observed that rigid, aromatized chromophores generally led to increased excited-state lifetimes by decreasing radiative rates of fluorescence decay.
- Tovar, John D.,Rose, Aimee,Swager, Timothy M.
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p. 7762 - 7769
(2007/10/03)
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- Methyl- and methoxy-substituted di[1,4]benzodithiio[2,3-b:2,3-e]-pyridines as new electron donor compounds: Synthesis, molecular structure, electrochemical properties, and EPR studies
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Two new derivatives of di[1,4]benzodithiino[2,3-b:2,3-e]pyridine (5) tetrasubstituted with methyl (7) and methoxy (8) groups at the 2,3,9 and 10 positions have been prepared from 2,3,5,6-tetrachloropyridine, by cyclization reaction with the bidentate nucleophiles, 4,5-dimethyl-and 4,5-dimethoxy-benzene-1,2-dithiol. Cyclic voltammograms for the oxidation of both polyheterocyclic compounds 7 and 8 in CH2Cl2 exhibit two consecutive redox couples. The first pairs are due to the equilibria between the initial compounds and their radical cations, while in the second couples, the electrogenerated radical cations are in equilibrium with the corresponding dications. Radical cations of these molecules have been generated in fluid solution, by oxidation of the parent compounds with thallium(III) trifluoroacetate in trifluoroacetic acid in the case of 7, and by irradiation of a CH2Cl2 solution containing trifluoroacetic acid (10%) in the case of 8. Both species were analyzed by electron paramagnetic resonance (EPR). X-Ray analysis of the molecular structures of both 7 and 8 shows a stable chair-shaped conformation with interplanar angles between the phenyl rings and the pyridine ring of 139.9 and 141.4° for 7 and 133.7° for 8.
- Bueno,Esteve,Irurre,Brillas,Torrelles,Rius,Alvarez-Larena,Piniella,Aleman,Julia
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p. 1503 - 1512
(2007/10/03)
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- Electrophilic Aromatic Bromination Using Bromodimethylsulfoniuin Bromide Generated in Situ
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It has been shown that bromodimethylsulfonium bromide, generated in situ by treating dimethyl sulfoxide with aqueous hydrobromic acid, is a milder and more selective reagent for electrophilic aromatic bromination than elemental bromine.
- Majetich, George,Hicks, Rodgers,Reister, Steven
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p. 4321 - 4326
(2007/10/03)
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- Transition-metal Complexes of Crown Ether Benzodithiolenes
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Three new dithiolene ligands have been synthesized, two of which have the novel feature of a crown ether ring attached directly to the benzene ring of an aryl dithiolene.Complexes with transition metals have been prepared and their (1)H, (13)C NMR, UV/VIS and electrochemical properties recorded.The information obtained appears to reflect variations in the degree of delocalisation in the metallodithiolene ring within the series of complex types.
- Lowe, Nigel D.,Garner, C. David
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p. 2197 - 2208
(2007/10/02)
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- 13C and 17O NMR Study of Methoxy Groups in Chlorinated Di- and Trimethoxybenzenes
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13C and 17O NMR data for the methoxy groups in isomeric 1,2-, 1,3- and 1,4-dimethoxybenzenes, 1,2,3-trimethoxybenzenes and most of their chlorinated derivatives and some related brominated compounds were measured for CDCl3 solutions.The 17O NMR chemical shifts show up to 60 ppm dispersion.Comparison between the compounds with and without adjacent chlorine atoms (2,6-di- and 2,4,6-trisubstitution) also showed a clear methoxy carbon chemical shift change.The number and position of the chlorine atoms in the aromatic ring give small but observable effects on the 17O NMR chemical shifts of the methoxy group if it is coplanar with the aromatic plane.Similarly, the degree and nature of the substitution have a minor effect (about 1 Hz) on the 1J(CH) direct coupling values.
- Knuutinen, J.,Kolehmainen, E.
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p. 315 - 317
(2007/10/02)
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- 1H and 13C NMR studies of the conformational mobility of 1,2-dimethoxybenzene in solution
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1H and 13C NMR spectral data are presented for 1,2-dimethoxy-α,α'-13C, as well as for a number of other anisole derivatives.For the title molecule, the coupling constants between the 13C nucleus in the side chain and the para ring proton or 13C nucleus in the benzene ring show that the expectation value of sin2 θ is very near 0.2 at 300 K, where θ is the angle by which the methoxy groups twist out of the aromatic plane.This value of 2 θ> is much larger than that of 0.05 for anisole in solution, emphasizing the greater conformational mobility of the methoxy groups in 1,2-dimethoxybenzene (DMB).Long-range coupling constants between the methyl and ring protons in DMB are also discussed and compared with those in anisol and some of its derivatives.The preponderance of conformations with large values of θ, thought to occur in the vapor, disappears in solution at ambient temperatures.Under these conditions, the molecule is perhaps best described as preferring a planar conformation in which, however, the methoxy groups undergo excursions in θ whose average value is near 25 deg C.
- Schaefer, Ted,Sebastian, Rudy,Lemire, Alberta,Penner, Glenn H.
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p. 1393 - 1398
(2007/10/02)
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- TRANSFORMATIONS PHOTOCHIMIQUES d'ENDOPEROXYDES DERIVES d'HYDROCARBURES AROMATIQUES POLYCYCLIQUES-I; CAS DU PHOTOOXYDE DE DIPHENYL-9,10 ANTHRACENE; OBTENTION ET PROPRIETES DU DIEPOXYDE ISOMERE
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When irradiated at long wavelengths (λ>=435 nm), the 9,10-endoperoxide of 9,10-diphenylanthracene 1a isomerizes to the 4a,10:9,9a-diepoxide 4a, which can be isolated at low temperature.On warming at 20-25 deg C, 4a gives only the benzocyclobutenic diether 6a by electrocycling ring opening and cyclisation, whereas under irradiation it undergoes, degradation to 10-hydroxy-10-phenyl-9-anthrone 7a and isomerizations to the bicyclic acetal 8a and to the benzofurobenzofuran 9a.These transformations of 4a explain previous results obtained when irradiating 1a under various conditions; their mechanisms are discussed.
- Rigaudi, J.,Scribe, P.,Breliere, C.
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p. 2585 - 2593
(2007/10/02)
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