- Stereospecificity and concertedness of Retro-Diels-Alder fragmentation in some diester systems upon chemical ionization
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Retro-Diels-Alder (RDA) fragmentation of cis- and trans-2,3-diethoxycarbonyl-5,6,7,8-dibenzobicyclo[2.2.2] octanes under isobutane and methane chemical ionization conditions is highly stereospecific, giving rise to protonated diethyl maleate and fumarate, respectively. This behaviour indicates a single-step concerted mechanism, analogous to the ground-state RDA process that occurs in neutral molecules in the condensed phase. The analogous dissociation is partially stereospecific in stereoisomeric endo-, exo- and trans-2,3-diethoxycarbonylbicyclo [2.2.1]heptanes and non-stereospecific in endo-, exo- and trans-2,3-diethoxycarbonyl-5,6-benzobicyclo [2.2.2]octanes, indicating the involvement of a stepwise mechanism in the latter two systems. The different behaviour of the above systems is explained in terms of the energy of the RDA fragmentation. The differentiation and quantitative estimates of protonated diethyl maleate and fumarate were obtained from collision-induced dissociation measurements.
- Denekamp,Weisz,Mandelbaum
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- Synthesis and biological evaluation of isoindoloisoquinolinone, pyroloisoquinolinone and benzoquinazolinone derivatives as poly(ADP-ribose) polymerase-1 inhibitors
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A series of novel fused isoquinolinones with isoindoloisoquinolinone, pyroloisoquinolinone, and benzoquinalizinone skeletons were synthesized from corresponding phenethylimides. The isoquinolinone derivatives were evaluated for their protective effect on chicken erythrocytes subjected to oxidative damage. The effect of isoquinolinone derivatives were analysed by estimation of cell viability, antioxidant enzyme activities, DNA damage (comet assay), PARP-1 inhibition assay and molecular docking of the compounds with PARP-1 active site. The compounds CRR-271, CRR-288 and CRR-224+225 showed significant protective effect at 100 μM concentration. The PARP-1 inhibition assay revealed the IC50 values of CRR-271, CRR-288 and CRR-224+225 as 200 nM, further molecular docking studies shows higher binding energies with PARP-1 active site. Interesting findings in this study suggest that the novel isoquinolinone derivatives inhibit PARP-1 activity and protect cells against oxidative DNA damage, which could be implemented in the treatment of inflammatory diseases.
- Suyavaran, Arumugam,Ramamurthy, Chitteti,Mareeswaran, Ramachandran,Shanthi, Yagna Viswa,Selvakumar, Jayaraman,Mangalaraj, Selvaraj,Kumar, Muthuvel Suresh,Ramanathan, Chinnasamy Ramaraj,Thirunavukkarasu, Chinnasamy
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- Discovery of novel small molecule inhibitors of S100P with in vitro anti-metastatic effects on pancreatic cancer cells
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S100P, a calcium-binding protein, is known to advance tumor progression and metastasis in pancreatic and several other cancers. Herein is described the in silico identification of a putative binding pocket of S100P to identify, synthesize and evaluate novel small molecules with the potential to selectively bind S100P and inhibit its activation of cell survival and metastatic pathways. The virtual screening of a drug-like database against the S100P model led to the identification of over 100 clusters of diverse scaffolds. A representative test set identified a number of structurally unrelated hits that inhibit S100P-RAGE interaction, measured by ELISA, and reduce in vitro cell invasion selectively in S100P-expressing pancreatic cancer cells at 10 μM. This study establishes a proof of concept in the potential for rational design of small molecule S100P inhibitors for drug candidate development.
- Camara, Ramatoulie,Ogbeni, Deborah,Gerstmann, Lisa,Ostovar, Mehrnoosh,Hurer, Ellie,Scott, Mark,Mahmoud, Nasir G.,Radon, Tomasz,Crnogorac-Jurcevic, Tatjana,Patel, Pryank,Mackenzie, Louise S.,Chau, David Y.S.,Kirton, Stewart B.,Rossiter, Sharon
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- Decorating the Edges of a 2D Polymer with a Fluorescence Label
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This work proves the existence and chemical addressability of defined edge groups of a 2D polymer. Pseudohexagonally prismatic single crystals consisting of layered stacks of a 2D polymer are used. They should expose anthracene-based edge groups at the six (100) but not at the two pseudohexagonal (001) and (001) faces. The crystals are reacted with the isotopically enriched dienophiles maleic anhydride and a C18-alkyl chain-modified maleimide. In both cases the corresponding Diels-Alder adducts between these reagents and the edge groups are formed as confirmed by solid state NMR spectroscopy. The same applies to a maleimide derivative carrying a BODIPY dye which was chosen for its fluorescence to be out of the range of the self-fluorescence of the 2D polymer crystals stemming from contained template molecules. If the crystals are excited at λ = 633 nm, their (100) faces and thus their rims fluoresce brightly, while the pseudohexagonal faces remain silent. This is visible when the crystals lie on a pseudohexagonal face. Lambda-mode laser scanning microscopy confirms this fluorescence to originate from the BODIPY dye. Micromechanical exfoliation of the dye-modified crystals results in thinner sheet packages which still exhibit BODIPY fluorescence right at the rim of these packages. This work establishes the chemical nature of the edge groups of a 2D polymer and is also the first implementation of an edge group modification similar to end group modifications of linear polymers.
- Zhao, Yingjie,Bernitzky, Richard H. M.,Kory, Max J.,Hofer, Gregor,Hofkens, Johan,Schlüter, A. Dieter
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- Reactions of polycyclic arene systems stabilized and activated by cyclopentadienylruthenium cations
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One vinylidene group of [(CpRu)(η6-dibenzo-p-quinodimethane)]+PF 6- (1) (Cp = η5-cyclopentadienyl), in which highly reactive dibenzo-p-quinodimethane is stabilized by coordination to ruthenium, underwent Diels-Alder cycloaddition from the exo face with 2,3-dimethyl-1,3-butadiene to give a novel spiro derivative of dibenzo-p-quinodimethane (2). X-ray analysis of 2 (C27H27F6PRu) confirmed its structure and showed it to crystallize in the monoclinic space group P21/n with a = 16.079(5) A?, b = 11.682(3) A?, c = 13.508(4) A?, β = 91.03(3)°, and Z = 4. The Cp* (Cp* = η5-pentamethylcyclopentadienyl) analogue of 1 did not react with 2,3-dimethyl-1,3-butadiene. The η6-localization effect of cyclopentadienylruthenium cations can also be used to activate polycyclic aromatic hydrocarbons toward Diels-Alder and catalytic hydrogenation reactions. [(Cp*Ru)(η6-anthracene)]+TfO- (3) underwent quantitative Diels-Alder reaction from the exo face with maleic anhydride under mild conditions (83°C) to give [trans-(endo-Cp*Ru)(η 6-9,10-dihydroanthracene-9,10-α,β-succinic acid anhydride)]+TfO- (4) selectively. Reaction of anthracene under identical conditions gave only 19% conversion. Reaction of maleic anhydride with [CpRu(η6-naphthalene)]+PF6- (6) was not successful. However, hydrogenation of 6 in methanol (1 atm, 24°C, 6 h) took place smoothly in the presence of a heterogeneous Pd/C catalyst to give [CpRu(η6-1,2,3,4-tetrahydronaphthalene)]+PF 6- (7) in high yield. The Cp* analogue of 6 gave similar results. Noncomplexed naphthalene remained largely unreacted under identical conditions (61% remaining), and a substantial proportion remained (32%) after 24 h. The Cp*Ru and CpRu groups in 4 and 7 can be removed by photolysis in acetonitrile to cleanly give 9,10-dihydroanthracene-9,10-α,β-succinic acid anhydride (5) and 1,2,3,4-tetrahydronaphthalene (8), respectively, as well as generating Cp- and Cp*-ruthenium tris(acetonitrile) salts, which can be used to make more complexed arene.
- Glatzhofer, Daniel T.,Liang, Yongwu,Funkhouser, Gary P.,Khan, Masood A.
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- Rational design of novel TLR4 ligands by in silico screening and their functional and structural characterization in vitro
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The purpose of this study was to identify new small molecules that possess activity on human toll-like receptor 4 associated with the myeloid differentiation protein 2 (hTLR4/MD2). Following current rational drug design principles, we firstly performed a ligand and structure based virtual screening of more than 130 000 compounds to discover until now unknown class of hTLR4/MD2 modulators that could be used as novel type of immunologic adjuvants. The core of the in silico study was molecular docking of flexible ligands in a partially flexible hTLR4/MD2 receptor model using a peta-flops-scale supercomputer. The most promising substances resulting from this study, related to anthracene-succimide hybrids, were synthesized and tested. The best prepared candidate exhibited 80% of Monophosphoryl Lipid A in vitro agonistic activity in cell lines expressing hTLR4/MD2.
- Honegr, Jan,Malinak, David,Dolezal, Rafael,Soukup, Ondrej,Benkova, Marketa,Hroch, Lukas,Benek, Ondrej,Janockova, Jana,Kuca, Kamil,Prymula, Roman
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- Experimental survey of the kinetics of acene Diels-Alder reactions
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The rate profiles for pseudo-first-order reactions between tetracene and selected dienophiles. The reactivity ranged roughly two orders of magnitude, from the slowest reacting dienophile (2,3-dichloromaleic anhydride, light blue) to the fastest dienophile (N-methylmaleimide, orange). Other utilized dienophiles included, in order of reactivity, maleic anhydride (navy), tetrafluoro-1,4-benzoquinone (purple), and p-benzoquinone (green).
- Qualizza, Brittni A.,Ciszek, Jacob W.
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- Structure correlation study of some DielsAlder cycloadducts of anthracene
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Crystal structures of some DielsAlder cycloadducts of anthracene and a variety of dienophiles reveal structural effects consistent with the manifestation of the early stages of the retro DielsAlder reaction in the ground state structure. The symmetrical cycloadducts 3 and 4 reveal a qualitative relationship between structure and reactivity, whereas the cycloadducts of 9-methoxyanthracene show structural effects suggestive of the early stages of an asynchronous retro DielsAlder reaction. CSIRO 2009.
- Goh, Yit W.,White, Jonathan M.
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- Lipase catalyzed desymmetrization of roof shape cis-11,12-bis(hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene
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Biocatalyzed desymmetrization of roof shape meso cis-11,12-bis(hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene has been achieved. The absolute configuration of the product is established by single crystal X-ray analysis of its diastereomer prepared with R-chloropropionic acid. Single crystal analysis of the chiral roof shape monoacetate shows a P-helical motif due to the extended intramolecular hydrogen bonding while the racemic sample exhibits intermolecular double hydrogen bonding holding two molecules together as a dimmer.
- Jain, Nilesh,Bedekar, Ashutosh V.
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- Design and synthesis of c3-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence
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We have developed an efficient synthetic strategy to assemble C3-symmetric molecules containing propellane moieties as end groups and a benzene ring as a central core. The synthesis of these C3-symmetric molecules involves simple starting materials. Our approach to C3-symmetric compounds relies on a Diels–Alder reaction, cyclotrimerization and ring-closing metathesis as key steps.
- Kotha, Sambasivarao,Todeti, Saidulu,Aswar, Vikas R.
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- Stereo-specific synthesis of hydroanthracene-dicarboximides
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Compound 3, N-((1S)-1-cyclohexylethyl)-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)- dicarboximide-1,2,3,4-octahydro, was obtained by ruthenium-assisted hydrogenation of the hydroanthracene-dicarboximide 2 under mild conditions (3 bar H2 and room temperature). In contrast to other related compounds, dicarboximides 2 and 3 were stereo-selectively obtained, confirmed by both solid state (X-ray diffraction) and solution (NMR). This selectivity denoted a hindered rotation around the N-CH axis together with the aromatic hydrogen bond acceptor behaviour of the hydroanthracene skeleton towards a methylene of the cyclohexyl group of the imide moiety. In addition, the nature of the metallic species involved in the hydrogenation process was also investigated.
- Sanhes, Delphine,Favier, Isabelle,Saffon, Nathalie,Teuma, Emmanuelle,Gómez, Montserrat
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- Crystal Inclusion of Oligocyclic Anhydrides Containing 9,10-Dihydro-9,10-ethanoanthracene Contructional Units - Crystal Structure of a Benzene Clathrate
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A series of rigid oligocyclic anhydrides comprising a characteristic 9,10-dihydro-9,10-ethanoanthracene framework have been shown to form crystaline inclusion compounds (clathrates) with small organic molecules, in particular of five- and six-membered ring types.Inclusion formation depends on the number of substituents (bromine atoms).The X-ray crystal stucture of the clathrate 4 * benzene (2:1) is reported: monoclinic (P21/c), a=8.599(4), b=9.732(5), c=21.023(10) Angstroem, β=92.03(4) deg, Z=4.The benzene guest molecules are located in lattice cavities between the bulky host molecules around the crystallographic symmetry centres, and are somewhat disordered.The cocrystal is held together by weak van der Waals forces.The stuctural model refined to R=0.046 for 1903 reflections with I>3δ(I).
- Weber, E.,Finge, S.,Reutel, C.,Csoeregh, I.,Gallardo, O.
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- Polycyclic Maleimide-based Scaffold as New Privileged Structure for Navigating the Cannabinoid System Opportunities
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The discovery of the relevant role played by a dysregulation of the endogenous cannabinoid system in several pathological conditions has prompted an extensive research in this field. In this Letter, a series of cannabinoid receptor ligands bearing a previously unexplored polycyclic scaffold was designed and synthesized, in order to evaluate the potential of a new easily affordable privileged structure. The new compounds showed an appreciable affinity and a significant selectivity for the CB2 receptor and are endowed with an intriguing noncompetitive antagonist behavior. Due to the ability of the polycyclic structure to be easily modified in different ways, these compounds could represent convenient chemical tools to be exploited in order to better understand the endocannabinoid system impact on physiopathological conditions.
- Bisi, Alessandra,Mokhtar Mahmoud, Alì,Allará, Marco,Naldi, Marina,Belluti, Federica,Gobbi, Silvia,Ligresti, Alessia,Rampa, Angela
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- Diels-Alder cycloadditions by microwave-assisted, continuous flow organic synthesis (MACOS): The role of metal films in the flow tube
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Thin Pd films have been deposited on the inside of capillary-sized tubes through which compounds undergoing Diels-Alder reactions have been flowed while being heated with microwave irradiation; dramatic rate accelerations are observed in the presence of the film, which has been shown to play both a heating and catalytic role. The Royal Society of Chemistry.
- Shore, Gjergji,Organ, Michael G.
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- Electrostatically Driven CO-πAromatic Interactions
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A series of N-arylimide molecular balances were developed to study and measure carbonyl-aromatic (CO-π) interactions. Carbonyl oxygens were observed to form repulsive interactions with unsubstituted arenes and attractive interactions with electron-deficient arenes with multiple electron-withdrawing groups. The repulsive and attractive CO-πaromatic interactions were well-correlated to electrostatic parameters, which allowed accurate predictions of the interaction energies based on the electrostatic potentials of the carbonyl and arene surfaces. Due to the pronounced electrostatic polarization of the C=O bond, the CO-πaromatic interaction was stronger than the previously studied oxygen-πand halogen-πaromatic interactions.
- Li, Ping,Vik, Erik C.,Maier, Josef M.,Karki, Ishwor,Strickland, Sharon M. S.,Umana, Jessica M.,Smith, Mark D.,Pellechia, Perry J.,Shimizu, Ken D.
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- Synthesis of propellanes containing a bicyclo[2.2.2]octene unit: Via the Diels-Alder reaction and ring-closing metathesis as key steps
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The synthesis of propellanes containing bicyclo[2.2.2]octene via olefin metathesis approach is less explored. Herein, we describe a simple and convenient method to synthesize propellane derivatives containing a bicyclo[2.2.2]octene unit which are structurally similar to 11β-HSD1 inhibitors by sequential usage of the Diels-Alder reaction, C-allylation and ring-closing metathesis (RCM) as the key steps. Additionally, we expanded this approach to an endo-tricyclo[4.2.2.02,5]decene derivative which is a useful monomer for polymer synthesis and we have also synthesized basketene and anthracene-based propellanes using the same strategy.
- Kotha, Sambasivarao,Pulletikurti, Sunil
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p. 14906 - 14915
(2018/04/30)
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- Iron-Catalyzed Ring-Closing C?O/C?O Metathesis of Aliphatic Ethers
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Among all metathesis reactions known to date in organic chemistry, the metathesis of multiple bonds such as alkenes and alkynes has evolved into one of the most powerful methods to construct molecular complexity. In contrast, metathesis reactions involving single bonds are scarce and far less developed, particularly in the context of synthetically valuable ring-closing reactions. Herein, we report an iron-catalyzed ring-closing metathesis of aliphatic ethers for the synthesis of substituted tetrahydropyrans and tetrahydrofurans, as well as morpholines and polycyclic ethers. This transformation is enabled by a simple iron catalyst and likely proceeds via cyclic oxonium intermediates.
- Biberger, Tobias,Makai, Szabolcs,Lian, Zhong,Morandi, Bill
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supporting information
p. 6940 - 6944
(2018/05/14)
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- Design and Performance Validation of a Conductively Heated Sealed-Vessel Reactor for Organic Synthesis
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A newly designed robust and safe laboratory scale reactor for syntheses under sealed-vessel conditions at 250 °C maximum temperature and 20 bar maximum pressure is presented. The reactor employs conductive heating of a sealed glass vessel via a stainless steel heating jacket and implements both online temperature and pressure monitoring in addition to magnetic stirring. Reactions are performed in 10 mL borosilicate vials that are sealed with a silicone cap and Teflon septum and allow syntheses to be performed on a 2-6 mL scale. This conductively heated reactor is compared to a standard single-mode sealed-vessel microwave instrument with respect to heating and cooling performance, stirring efficiency, and temperature and pressure control. Importantly, comparison of the reaction outcome for a number of different synthetic transformations performed side by side in the new device and a standard microwave reactor suggest that results obtained using microwave conditions can be readily mimicked in the operationally much simpler and smaller conventionally heated device.
- Obermayer, David,Znidar, Desiree,Glotz, Gabriel,Stadler, Alexander,Dallinger, Doris,Oliver Kappe
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p. 11788 - 11801
(2016/12/09)
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- ANTHRACENE BASED COMPOUNDS AND THEIR USES
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The present invention relates to compounds of the general formula (A) and their applicability for use in the treatment or prophylaxis of a disease, in particular for use as in treatment of cancer, in particular for use as in treatment of pancreatic cancer, in particular as inhibitors of S100P/RAGE interaction in pancreatic cancer. In summary herein are presented a group of compounds for use as in treatment of cancer, in particular as inhibitors of S100P/RAGE interaction in pancreatic cancer. The compounds have general formula (A): (A) or may be a pharmaceutically acceptable salt, solvate, hydrate, polymorph, prodrug, codrug, cocrystal, tautomer, racemate, stereoisomer or mixture thereof. X is independently NO2 or H; and Y is independently H or a side group. The compounds all have a lower fused ring system based on nitroanthracene or anthracene. The group Y attached to the N of the succinimide group varies between the compounds. For example, Y may be substituted or non-substituted benzene ring. Alternatively, in some examples Y is a heteroaromatic system. It has been discovered from studies by the inventors that the compounds described will inhibit S100P/RAGE interaction and are therefore useful for treating pancreatic cancer.
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Page/Page column 26
(2016/12/01)
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- Fluorescent cyanoacrylate monomers and polymers for fingermark development
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Cyanoacrylate esters with fluorescent side groups were synthesized and tested as agents for latent fingerprint development. Reactive monomers with benzyl, anthracyl, naphthyl, fluorenyl, propagyl, and cyanomethyl side groups were synthesized using the formation of an ethyl cyanoacrylate, anthracene adduct, followed by hydrolysis of the ethyl ester to the acid and esterification with a desired alcohol, and finally release of the monomer by retro-Diels-Alder with maleic anhydride. Monomers were prepared in high yield and purity as determined by spectral analysis. Attempts to synthesize these monomers from poly(ethyl cyanoacrylate) by transesterification and depolymerization resulted in low yields and low purity. The synthesized fluorescent monomers were found to be effective for latent fingerprint development in solution forming clear fluorescent fingerprint images suitable for forensic fingerprint comparison. These monomers can complement the current use of the commonly used nonfluorescent ethyl cyanoacrylate monomers for fingerprint development.
- Bentolila, Alfonso,Totre, Jalindar,Zozulia, Ilana,Levin-Elad, Michal,Domb, Abraham J.
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p. 4822 - 4828
(2013/07/26)
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- Shape takes the lead: Templating organic 3D-frameworks around organometallic sandwich compounds
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The novel organic-organometallic crystalline compounds [(η5- C5H5)2Co][(cis-deccaH)(cis-deccaH2)] (1), [(η5-C5H5)2Co][(cis- deccaH)(cis-deccaH2)]?H2O (2), [(η5- C5H5)2Co][trans-deccaH] (3), [(η5-C5H5)2Co][(trans-deccaH) (trans-deccaH2)] (4), [(η5-C5Me 5)2Co][cis-deccaH] (5), [(η5-C 5Me5)2Co][trans-deccaH]?4H2O (6), and [(η6-C6H6)2Cr][trans- deccaH] (7) have been prepared by direct reaction of neutral [(η5-C5H5)2Co], [(η5-C5Me5)2Co], and [(η6-C6H6)2Cr] with the organic compounds cis-9,10-dihydroanthracene-9,10-α,β-succinic acid anhydride and trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (cis-decca and trans-deccaH2, respectively). The organic building blocks have been chosen because of their three-stem star-like shape and the difference in hydrogen-bonding capacity. It is shown that the formation of a honeycomb-type anionic arrangement around the organometallic cations does not require the assistance of strong hydrogen-bonding interactions. Depending on the stoichiometric ratio and on the presence of water molecules, rectangular and layered crystal packings are also obtained.
- Braga, Dario,D'Agostino, Simone,Grepioni, Fabrizia
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experimental part
p. 1688 - 1695
(2012/04/23)
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- Do deuteriums form stronger CH-π interactions?
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The D/H isotope effect for the CH-π interaction was studied experimentally and computationally. First, a series of molecular balances that are very sensitive to changes in the strength of the CH-π interactions in solution were designed. Balances with deuterated and non-deuterated alkyl groups were synthesized, and their intramolecular CH-π interactions were compared. The geometries of their intramolecular CH-π and CD-π interactions were characterized in the solid state by X-ray analysis, and the strength of each interaction was characterized in solution by the folded/unfolded ratio as measured by 1H NMR spectra. Second, the relative strengths of the CH-π and CD-π interactions were also assessed computationally using dispersion-corrected DFT (PDE-D2/6-31+G*). No significant differencee was observed in either the experimental or theoretical studies, indicating that the D/H isotope effect for the CH-π interaction is either very small or nonexistent.
- Zhao, Chen,Parrish, Robert M.,Smith, Mark D.,Pellechia, Perry J.,Sherrill, C. David,Shimizu, Ken D.
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supporting information
p. 14306 - 14309
(2012/10/30)
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- Synthesis and characterization of four alkyl 2-cyanoacrylate monomers and their precursors for use in latent fingerprint detection
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Four novel cyanoacrylates, 2-cyanoethyl 2-cyanoacrylate, 1-cyanoethyl 2-cyanoacrylate, trideuteromethyl 2-cyanoacrylate and pentadeuteroethyl 2-cyanoacrylate have been synthesized using a Diels-Alder protection/ deprotection route involving anthracene. The common route for the synthesis of alkyl 2-cyanoacrylates was found to be unsatisfactory for the production of small quantities of the targeted cyanoacrylates, which have potential as reagents for the mid-infrared spectral imaging of fingerprints on difficult surfaces. Copyright
- Tahtouh, Mark,Kalman, John R.,Reedy, Brian J.
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p. 257 - 277
(2011/10/08)
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- Reductions of challenging organic substrates by a nickel complex of a noninnocent crown carbene ligand
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The first crown-tetracarbene complex of Ni(II) has been prepared, and its crystal structure determined. The complex can be reduced by Na/Hg, with an uptake of two electrons. The reduced complex reductively cleaves arenesulfonamides, including those derived from secondary aliphatic amines, and effects Birch reduction of anthracenes as well as reductive cleavage of stilbene oxides. Computational studies show that the orbital that receives electrons upon reduction of the complex 2 is predominantly based on the crown carbene ligand and also that the HOMO of the parent complex 2 is based on the ligand.
- Findlay, Neil J.,Park, Stuart R.,Schoenebeck, Franziska,Cahard, Elise,Zhou, Sheng-Ze,Berlouis, Leonard E. A.,Spicer, Mark D.,Tuttle, Tell,Murphy, John A.
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supporting information; experimental part
p. 15462 - 15464
(2011/02/22)
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- Selectivity for the methoxycarbonylation of ethylene versus CO-ethylene copolymerization with catalysts based on C4-bridged bidentate phosphines and phospholes
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The C4-bridged phospholes 11,12-bis(2,3,4,5-tetramethylphospholylmethyl)-9,10-dihydro-9,10-ethano- anthracene (cis, 4a; trans, 4b) and diphosphines 11,12-bis(diphenylphosphinomethyl)-9,10-dihydro-9,10-ethano-anthracene (cis, 5a; trans, 5b) and their corresponding palladium complexes [(P-P)PdCl2] (6a-d) have been prepared and characterized. Single-crystal X-ray analyses of 6a-d have been undertaken and they reveal that 4a and b and 5a and b coordinate in a bidentate manner forming seven-membered chelate rings with natural bite angles between 98.62 and 100.30°. The palladium-catalyzed carbonylation of ethylene has been studied using 4a and b and 5a and b. Catalyst mixtures generated from 4a and b, palladium acetate and methanesulfonic acid are selective for the copolymerization of ethylene with carbon monoxide, generating low molecular weight polymers. Surprisingly, the activity of catalyst systems based on cis-(4a) is markedly higher than that based on its trans-isomer, 4b. The marked influence of the nature of the four-carbon tether is highlighted by comparative catalyst testing with [{1,4-bis(2,3,4,5-tetramethylphospholyl)butane}Pd(OAc)2], which rapidly decomposes under the conditions used for copolymerization. In contrast, under identical conditions catalyst mixtures formed from 5a and b show a marked dependence of the selectivity on the stereochemistry of the ethano-anthracene tether, the former generating a low molecular weight copolymer while the latter generate mainly methyl propanoate. Interestingly, polyketone generated from catalysts based on bisphosphole 4a has a markedly higher average molecular weight than that formed using its diphenylphosphino counterpart, 5a.
- Doherty, Simon,Robins, Edward G.,Knight, Julian G.,Newman, Colin R.,Rhodes, Barrie,Champkin, Paul A.,Clegg, William
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p. 182 - 196
(2007/10/03)
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- Microwave-assisted Diels-Alder reaction supported on graphite
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The coupling of graphite (as a support) with microwaves (as an energy source), a new type of "dry reaction", was studied for some Diels-Alder reactions involving anthracene and azadienes. Graphite is responsible for a high-temperature gradient leading to increased reaction rates as compared to conventional procedures using a solvent. VCH Verlagsgesellschaft mbH, 1996.
- Garrigues, Bernard,Laporte, Christian,Laurent, Regis,Laporterie, Andre,Dubac, Jacques
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p. 739 - 741
(2007/10/03)
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- APPLICATION OF COMMERCIAL MICROWAVE OVENS TO ORGANIC SYNTHESIS.
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Commercial microwave ovens have been safely used to dramatically reduce the reaction times (at comparable yield) of Diels-Alder, Claisen, and ene reactions.Significant solvent effects were also observed.
- Giguere, Raymond J.,Bray, Terry L.,Duncan, Scott M.
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p. 4945 - 4948
(2007/10/02)
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- A Kinetic Study of Reactions of Substituted Anthracenes with Maleic Anhydride
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Kinetic data for the Diels-Alder addition of 2-, 9- and 9,10-disubstituted anthracenes with maleic anhydride are interpreted in terms of FMO-theory.While the simplest form of FMO-theory does not give satisfactory results, inclusion of eigenvector coefficients at the reacting centers does provide an improvement.
- Mielert, Albrecht,Braig, Christa,Sauer, Juergen,Martelli, Jaques,Sustmann, Reiner
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p. 954 - 970
(2007/10/02)
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