- Air-Sensitive Photoredox Catalysis Performed under Aerobic Conditions in Gel Networks
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In this work, we demonstrate that useful C-C bond-forming photoredox catalysis can be performed in air using easily prepared gel networks as reaction media to give similar results as are obtained under inert atmosphere conditions. These reactions are completely inhibited in homogeneous solution in air. However, the supramolecular fibrillar gel networks confine the reactants and block oxygen diffusion, allowing air-sensitive catalytic activity under ambient conditions. We investigate the mechanism of this remarkable protection, focusing on the boundary effect in the self-assembled supramolecular gels that enhances the rates of productive reactions over diffusion-controlled quenching of excited states. Our observations suggest the occurrence of triplet-sensitized chemical reactions in the gel networks within the compartmentalized solvent pools held between the nanofibers. The combination of enhanced viscosity and added interfaces in supramolecular gel media seems to be a key factor in facilitating the reactions under aerobic conditions.
- H?ring, Marleen,Abramov, Alex,Okumura, Keisuke,Ghosh, Indrajit,K?nig, Burkhard,Yanai, Nobuhiro,Kimizuka, Nobuo,Díaz Díaz, David
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p. 7928 - 7938
(2018/06/04)
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- Synthesis, electrochemistry, and gas-phase photoelectron spectroscopic and theoretical studies of 3,6-bis(perfluoroalkyl)-1,2-dithiins
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3,6-Bis(trifluoromethyl)- and 3,6-bis(pentafluoroethyl)-1,2-dithiin (la,b), the first known perfluoroalkyl-substituted 1,2-dithiins, were synthesized from (Z,Z)-1,4-bis(tert-butylthio)-1,3-butadiene (2) to evaluate the effects of electron-withdrawing groups on the ionization and oxidation potentials of 1,2-dithiins. Analysis of the photoelectron spectra of la and lb provided a basis for assigning orbital compositions. Ab initio calculations on these compounds showed that they adopt a twist geometry as does 1,2-dithiin (1c) itself. Cyclic voltammetric studies on la and lb revealed a reversible oxidation followed by an irreversible oxidation at much more positive potentials than for 1,2-dithiin and 3,6-dimethyl-1,2-dithiin (1d). The oxidation potentials determined electrochemically do not correlate with the ionization potentials determined by photoelectron spectroscopy. This result supports the previously advanced hypothesis that there is a geometry change on electrochemical oxidation leading to a planar radical cation.
- Lorance, Edward D.,Glass, Richard S.,Block, Eric,Li, Xiaojie
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p. 8110 - 8114
(2007/10/03)
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- SYNTHESIS AND POLYMERISATION OF ETHYNYLTHIOPHENES AND ETHYNYLFURANS CONTAINING TRIFLUORMETHYL GROUPS
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Fluorination of thiophenedicarboxylic acid with sulfur tetrafluoride in the presence of anhydrous hydrogen fluoride provided mono and bis(trifluoromethyl)thiophenes in moderate yields.Ethynylthiophenes and ethynylfurans containing trifluoromethyl groups were prepared via 2,2-dichloro-1-fluorovinyl compounds.In polymerizations using transitions metal catalysts, 3-ethynylthiophenes gave polymers in high yields, which were soluble in THF and/or fluorocompounds, while 2-ethynylthiophenes polymerized in low yields.In γ-ray induced polymerization, only 2,5-bis(trifluoromethyl)-3-ethynylthiophene afforded the corresponding polymers.Thermal decomposition temperatures of polymers obtained increased by introduction of the trifluoromethyl groups as well as the methyl groups.
- Nishida, Masakazu,Fujii, Shozo,Aoki, Toshiki,Hayakawa, Yoshio,Muramatsu, Hiroshige,Morita, Tomohiko
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p. 445 - 459
(2007/10/02)
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- PHOTOISOMERISATION OF BIS(TRIFLUOROMETHYL)THIOPHENES
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The photolysis of 2,3-bis(trifluoromethyl)thiophene gave an equilibrium mixture of 2,3- and 3,4-bis(trifluoromethyl)Dewar thiophenes, while that of 2,5-bis(trifluoromethyl)thiophene gave 2,4-bis(trifluoromethyl)thiophene, which seemed to be formed through an intermediate other than the Dewar form.
- Kobayashi, Yoshiro,Kawada, Kosuke,Ando, Akira,Kumadaki, Itsumaro
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p. 1917 - 1920
(2007/10/02)
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- Thiirene formation in the reactions of sulfur atoms with alkynes
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The gas phase reactions of S(1D2) and S(3PJ) atoms with alkynes have been studied by photolyzing COS in the presence of CHCH, CF3CCH, and CF3CCCF3.In the reactions with CHCH, CS2, benzene, and thiophene were formed; with CF3CCH, eight products found with disubstituted thiophenes and trisubstituted benzenes as the major products.In the case of CF3CCCF3, only perfluorotetramethylthiophene was detected at low conversion but at long photolysis several new products were observed.Many of the reaction products characterized here have not been reported before.The formation and distribution of the reaction products could be rationalized by an overall mechanism in which the formation of the highly reactive primary adducts, thiirene and thioformylmethylene, is followed by bimolecular reactions yielding the principal end products.The formation of minor products could be explained by secondary photoisomerizations, secondary photolysis, and by secondary decompositions and the secondary reactions of sulfur atoms with primary products.
- Verkoczy, Bela,Sherwood, Alden G.,Safarik, Imre,Strausz, Otto P.
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p. 2268 - 2281
(2007/10/02)
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