- Conductance of single triangular dehydrobenzo[12]annulene derivative bridged between Au electrodes
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A triangular dehydrobenzo[12]annulene (DBA) molecule bridged between Au electrodes was investigated by scanning tunneling microscopy break junction technique. The conductance of the single DBA molecule was determined to be 2.5 × 10-5 G0/s
- Kiguchi, Manabu,Tahara, Kazukuni,Takahashi, Yuuta,Hasui, Kensuke,Tobe, Yoshito
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- Photolysis of regioisomeric diazides of 1,2-diphenylacetylenes studies by matrix-isolation spectroscopy and DFT calculations.
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A series of diazides of 1,2-diphenylacetylenes was photolyzed in matrices at low temperature and transient photoproducts were characterized by using IR, UV/vis methods combined with ESR studies. Theoretical calculations were also used to understand the experimental findings. The introduction of phenylethynyl groups on phenyl azides has little effect on the photochemical pathway. Thus, upon photoexcitation, (phenylethynyl)phenyl azides afforded the corresponding triplet nitrene, which is in photoequilibrium with the corresponding azacycloheptatetraene. In marked contrast, azidophenylethynyl groups exhibited a dramatic effect not only on the photochemical pathway of phenyl azides but also on the electronic and molecular structure of the photoproducts. The patterns of the effect depended upon the relative position of azide groups in the diphenylacetylene unit. Whenever two azide groups were situated in a conjugating position with respect to each other, as in p,p'-, o,o'-, and p,o'-bis(azides), the azides always resulted in the formation of a quinoidal diimine diradical in which unpaired electrons were extensively delocalizedin the pi-conjugation. The situation changed rather dramatically when azide groups were introduced in the meta position. Thus, the formation of azacycloheptatetraene was noted in the photolysis of the m.m'-isomer. ESR studies indicated the generation of a quintet state that was shown to be a thermally populated state with a very small energy gap of ca. 100 cal mol(-1). The m,p'-isomer was shown to be an excellent precursor for the high-spin quintet dinitrene.The IR spectra of the photoproduct showed no bands ascribable to azacycloheptatetraene. The observed spectra were in good agreement with that calculated for the quintet state. Strong EPR signals assignable to the quintet state were observed, along with rather weak signals due to mononitrenes. Moreover, the quintet bis(nitrene) was rather photostable under these conditions.
- Tomioka, Hideo,Sawai, Shinji
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- Linear free-energy correlation analysis of the electronic effects of the substituents in the Sonogashira coupling reaction
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Relative rate constants (krel) for the Sonogashira coupling were determined in competitive reactions between iodobenzene and a series of para- and meta-substituted iodobenzenes and compared to the charge on iodine and the z-component of the qua
- Gottardo, Christine,Kraft, Thomas M.,Hossain, M. Selim,Zawada, Peter V.,Muchall, Heidi M.
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- Design, synthesis, and structure-activity relationship of 7-propanamide benzoxaboroles as potent anticancer agents
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Benzoxaboroles, as a novel class of bioactive molecules with unique physicochemical properties, have been shown to possess excellent antimicrobial activities with tavaborole approved in 2014 as an antifungal drug. Although urgently needed, the investigation of benzoxaboroles as anticancer agents has been lacking so far. In this study, we report the design, synthesis, and anticancer structure-activity relationship of a series of 7-propanamide benzoxaboroles. Compounds 103 and 115 showed potent activity against ovarian cancer cells with IC50 values of 33 and 21 nM, respectively. Apoptosis was induced by these compounds and colony formation was effectively inhibited. Furthermore, they also showed excellent efficacy in ovarian tumor xenograft mouse model.
- Zhang, Jiong,Zhang, Jinyi,Hao, Guiyun,Xin, Weixiang,Yang, Fei,Zhu, Mingyan,Zhou, Huchen
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p. 6765 - 6784
(2019/08/20)
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- Catalytic Activation of Trimethylsilylacetylenes: A One-Pot Route to Unsymmetrical Acetylenes and Heterocycles
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For the synthesis of unsymmetrical acetylenes, a Sonogashira coupling-deprotection-Sonogashira coupling reaction sequence is often used. Removal of protecting groups requires harsh conditions or an excess of difficult to handle and expensive reagents. Herein, we disclose a novel catalytic method for the selective deprotection of trimethylsilylacetylenes in Sonogashira reaction. The reagent hexafluorosilicic acid, an inexpensive nontoxic compound, was used to promote the selective desilylation. This method enables the efficient synthesis of unsymmetric acetylenes with other silylated functional groups present. Further possibilities of the method were explored by synthesis of heterocycles.
- Lasányi, Dániel,Mészáros, ádám,Novák, Zoltán,Tolnai, Gergely L.
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p. 8281 - 8291
(2018/06/11)
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- Chiral helical oligotriazoles: New class of anion-binding catalysts for the asymmetric dearomatization of electron-deficient N -heteroarenes
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Helical chirality and selective anion-binding processes are key strategies used in nature to promote highly enantioselective chemical reactions. Although enormous efforts have been made to develop simple helical chiral systems and thus open new possibilities in asymmetric catalysis and synthesis, the efficient use of synthetic oligo- and polymeric helical chiral catalysts is still very challenging and rather unusual. In this work, structural unique chiral oligotriazoles have been developed as C-H bond-based anion-binding catalysts for the asymmetric dearomatization of N-heteroarenes. These rotational flexible catalysts adopt a reinforced chiral helical conformation upon binding to a chloride anion, allowing high levels of chirality transfer via a close chiral anion-pair complex with a preformed ionic substrate. This methodology offers a straightforward and potent entry to the synthesis of chiral (bioactive)heterocycles with added synthetic value from simple and abundant heteroarenes.
- Zurro, Mercedes,Asmus, S?ren,Beckendorf, Stephan,Mück-Lichtenfeld, Christian,Mancheo, Olga Garca
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supporting information
p. 13999 - 14002
(2015/01/08)
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- Determining the regioregularity in alkyne polycarbodiimides and their orthogonal modification of side chains to yield perfectly alternating functional polymers
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To understand the structure-property relationship in functional macromolecules through side chain modulation, both the accurate determination of the position of modifiable groups along the polymer chain and their subsequent modifications using high fidelity methods are crucial. In this report, the polymer microstructure of a helical alkyne polycarbodiimide has directly been probed through 15N NMR spectroscopy on isotopic labeled poly(N-(3-ethynylphenyl)-15N′-hexyl)carbodiimide and found to be a highly regioregular polymer structure. This polymer undergoes facile and quantitative CuAAC "click" chemistry, yielding perfectly alternating functional polymers. Advances have been made through the synthesis of new optically active alkyne polycarbodiimides with two independently modifiable pendant groups per repeat unit of polymers. Orthogonal postmodifications of the pendant groups were then performed to incorporate two different sets of small molecules in the repeat unit of polymers in a controlled manner and under mild reaction conditions using either sequential CuAAC "click" reactions when two dissimilar alkyne groups are present or a combination of CuAAC and thiol-ene click chemistries when pendant groups bear alkyne and vinyl moieties.
- Budhathoki-Uprety, Januka,Reuther, James F.,Novak, Bruce M.
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p. 8155 - 8165
(2013/01/15)
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- Determining the regioregularity in alkyne polycarbodiimides and their orthogonal modification of side chains to yield perfectly alternating functional polymers
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To understand the structure-property relationship in functional macromolecules through side chain modulation, both the accurate determination of the position of modifiable groups along the polymer chain and their subsequent modifications using high fideli
- Budhathoki-Uprety, Januka,Reuther, James F.,Novak, Bruce M.
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p. 8155 - 8165,11
(2012/12/13)
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- Sonogashira coupling with aqueous ammonia directed to the synthesis of azotolane derivatives
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Sonogashira coupling with aqueous ammonia is tolerable for the reaction of aryl iodides or terminal alkynes bearing an azobenzene group. The reaction of (4-heptyloxyphenyl)ethyne with (4-heptyloxyphenyl)-(4-iodophenyl)diazene in the presence of 1 mol% of
- Mohamed Ahmed, Mohamed S.,Mori, Atsunori
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p. 9977 - 9982
(2007/10/03)
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- Processes and intermediates for preparing anti-cancer compounds
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The present invention relates to methods and intermediates for preparing compounds of the formula 1 and the pharmaceutically acceptable salts and solvates thereof, as well as structurally related compounds, wherein R1, R2and R15are as defined herein. The foregoing compounds are useful in the treatment of hyperproliferative disorders, such as cancers, in mammals.
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- Palladium-catalyzed carbon-carbon coupling reactions using aryl Grignards
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Coupling reactions using Pd(PPh3)4 were investigated with a number of electron donating and electron withdrawing substituents. High yields were obtained with both types of substituents. In competitive reactions the electron-withdrawi
- Gottardo, Christine,Aguirre, Andrea
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p. 7091 - 7094
(2007/10/03)
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- Rapid homogeneous-phase sonogashira coupling reactions using controlled microwave heating
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A microwave-enhanced, rapid and efficient homogeneous-phase version of the Sonogashira reaction is presented. It has been applied to the coupling of aryl iodides, bromides, triflates, and aryl chloride, as well as pyridine and thiophene derivatives with t
- Erdelyi,Gogoll
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p. 4165 - 4169
(2007/10/03)
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- Phenylene ethynylene pentamers for organic electroluminescence
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An isomeric family of eighteen triisopropylsilyl-capped phenylene ethynylene pentamers (molecular formula C60H62Si2) has been prepared by using fast parallel synthesis, for organic electroluminescence. Each pentamer was grown on a polymer support of propylaminomethylated polystyrene by using a series of palladium-catalysed reactions between aryl iodides and alkynes. "Tea bag" technology was used to carry out several different reactions simultaneously in the same flask. Here I present the syntheses of the materials, compare their photoluminescence both in solution and in the solid state (amorphous thin films) and describe the incorporation of the most promising pentamer into organic electroluminescence devices.
- Anderson
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p. 4706 - 4714
(2007/10/03)
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- Selective and efficient access to ortho, meta and para ring-substituted phenylacetylene derivatives R-[C≡C-C6H4](x)-Y (Y:H, NO2, CN, I, NH2)
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ortho, meta and para isomers of iodo and amino ring-substituted phenylacetylene as well as rod-like arylacetylene derivatives were prepared by a simple synthetic route involving three consecutive reactions: the palladium-catalysed carbon-carbon bond forma
- Lavastre, Olivier,Cabioch, Sandrine,Dixneuf, Pierre H.,Vohlidal, Jiri
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p. 7595 - 7604
(2007/10/03)
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- PALLADIUM-CATALYSED REDUCTIVE ADDITION OF ARYL IODIDES TO ARYL AND ALKYLETHYNYLSILANES: A STEREO AND REGIOSELECTIVE ROUTE TO FUNCTIONALIZED 2,2-DISUBSTITUTED VINYLSILANES
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Aryl and alkylethynylsilanes are converted into 2,2-disubstituted vinylsilanes containing various common functional groups in the presence of aryl iodides, a palladium catalyst, formic acid, and a tertiary or secondary amine with high stereoselectivity an
- Arcadi, A.,Cacchi, S.,Marinelli, F.
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p. 6397 - 6400
(2007/10/02)
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