- Electrocatalytic asymmetric hydrogenation of α,β-unsaturated acids in a PEM reactor with cinchona-modified palladium catalysts
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We have developed an electrocatalytic asymmetric hydrogenation reaction using a proton-exchange membrane (PEM) reactor that employs a polymer electrolyte fuel cell and industrial electrolysis technologies. Reasonable enantioselectivities and excellent current efficiencies were obtained in the asymmetric hydrogenation of α-phenylcinnamic acid under mild conditions without adding a supporting electrolyte. The current density was crucial to achieving the improved results observed.
- Atobe, Mahito,Fukazawa, Atsushi,Hashimoto, Yasushi,Sato, Yasushi,Tanaka, Kenta
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- Desyl and phenacyl as versatile, photocatalytically cleavable protecting groups: A classic approach in a different (visible) light
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A highly efficient, catalytic strategy for the deprotection of classical phenacyl (Pac) as well as desyl (Dsy) protection groups has been developed using visible light photoredox catalysis. The deliberate use of a neutral two-phase acetonitrile/water mixture with K3PO4 applying catalytic amounts of [Ru(bpy)3](PF6)2 in combination with ascorbic acid is the key to this truly catalytic deprotection of Pac- and Dsy-protected carboxylic acids. Our mild yet robust protocol allows for fast and selective liberation of the free carboxylic acids in very good to quantitative yields, while only low catalyst loadings (1 mol %) are required. Both Pac and Dsy, easily introduced from commercially available precursors, can be applied for the direct protection of carboxylic acids and amino acids, offering orthogonality to a great variety of other common protecting groups. We further demonstrate the general applicability and versatility of these formerly underrated protecting groups in combination with our catalytic cleavage conditions, as underscored by the gained high functional group tolerance. Moreover, this method could successfully be adapted to the requirements of solidphase synthesis. As a proof of principle for an efficient visible light, photocatalytic linker cleavage, a Boc-protected tripeptide was split off from commercially available brominated Wang resin.
- Speckmeier, Elisabeth,Zeitler, Kirsten
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p. 6821 - 6826
(2017/11/06)
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- Efficient one-to-one coupling of easily available 1,3-dienes with carbon dioxide
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An efficient one-to-one coupling reaction of atmospheric pressure carbon dioxide with 1,3-dienes is realized for the first time through PSiP-pincer type palladium-catalyzed hydrocarboxylation. The reaction is applicable to various 1,3-dienes including easily available chemical feedstock such as 1,3-butadiene and isoprene. This protocol affords a highly useful method for the synthesis of β,γ-unsaturated carboxylic acid derivatives from CO2.
- Takaya, Jun,Sasano, Kota,Iwasawa, Nobuharu
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supporting information; experimental part
p. 1698 - 1701
(2011/05/04)
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- Morning glory-derived anticancer agents, and novel ipomoeassin compounds
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Ipomoeassin compounds derived from morning glory plant material (especially Ipomoea sp. from Suriname) are useful as anti-cancer agents. The novel compounds also are useful for treating neurodegenerative disorders (such as Alzheimer's disease) in human patients.
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Page/Page column 12
(2008/06/13)
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- Process for the hydrogenation of ethylenically unsaturated organic compounds and ruthenium catalysts for carrying out said process
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The present invention relates to a process for the hydrogenation of ethylenically unsaturated organic compounds. This process is carried out in a homogeneous medium containing a hydrogenation catalyst formed by a complex of ruthenium with a phosphine, which comprises two allylic groups as ligands on the Ru.
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