- A General Organocatalytic System for Enantioselective Radical Conjugate Additions to Enals
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Herein, we report a general iminium ion-based catalytic method for the enantioselective conjugate addition of carbon-centered radicals to aliphatic and aromatic enals. The process uses an organic photoredox catalyst, which absorbs blue light to generate radicals from stable precursors, in combination with a chiral amine catalyst, which secures a consistently high level of stereoselectivity. The generality of this catalytic platform is demonstrated by the stereoselective interception of a wide variety of radicals, including non-stabilized primary ones which are generally difficult to engage in asymmetric processes. The system also served to develop organocatalytic cascade reactions that combine an iminium-ion-based radical trap with an enamine-mediated step, affording stereochemically dense chiral products in one-step.
- Le Saux, Emilien,Ma, Dengke,Bonilla, Pablo,Holden, Catherine M.,Lustosa, Danilo,Melchiorre, Paolo
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supporting information
p. 5357 - 5362
(2021/02/01)
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- Acridine Photocatalysis: Insights into the Mechanism and Development of a Dual-Catalytic Direct Decarboxylative Conjugate Addition
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Conjugate addition is one of the most synthetically useful carbon-carbon bond-forming reactions; however, reactive carbon nucleophiles are typically required to effect the addition. Radical conjugate addition provides an avenue for replacing reactive nucleophiles with convenient radical precursors. Carboxylic acids can serve as simple and stable radical precursors by way of decarboxylation, but activation to reactive esters is typically necessary to facilitate the challenging decarboxylation. Here, we report a direct, dual-catalytic decarboxylative radical conjugate addition of a wide range of carboxylic acids that does not require acid preactivation and is enabled by the visible light-driven acridine photocatalysis interfaced with an efficient copper catalytic cycle. Mechanistic and computational studies provide insights into the roles of the ligands and metal species in the dual-catalytic process and the photocatalytic activity of substituted acridines.
- Arman, Hadi D.,Dang, Hang T.,Haug, Graham C.,Larionov, Oleg V.,Nguyen, Viet D.,Nguyen, Vu T.,Vuong, Ngan T. H.
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p. 11448 - 11457
(2020/11/17)
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- Scope and mechanism in palladium-catalyzed isomerizations of highly substituted allylic, homoallylic, and alkenyl alcohols
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Herein we report the palladium-catalyzed isomerization of highly substituted allylic alcohols and alkenyl alcohols by means of a single catalytic system. The operationally simple reaction protocol is applicable to a broad range of substrates and displays a wide functional group tolerance, and the products are usually isolated in high chemical yield. Experimental and computational mechanistic investigations provide complementary and converging evidence for a chain-walking process consisting of repeated migratory insertion/β-H elimination sequences. Interestingly, the catalyst does not dissociate from the substrate in the isomerization of allylic alcohols, whereas it disengages during the isomerization of alkenyl alcohols when additional substituents are present on the alkyl chain.
- Larionov, Evgeny,Lin, Luqing,Gune, Laure,Mazet, Clment
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supporting information
p. 16882 - 16894
(2015/01/09)
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- Access to high levels of molecular complexity by one-pot iridium/enamine asymmetric catalysis
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(Chemical Equation Presented) Independent workers with team spirit: A catalytic sequence that exploits the compatibility of (chiral) cationic iridium catalysts for the isomerization of primary allylic alcohols to aldehydes with organo-catalysts has been d
- Quintard, Adrien,Alexakis, Alexandre,Mazet, Clement
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supporting information; experimental part
p. 2354 - 2358
(2011/04/22)
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- Intrazeolite photooxygenation of chiral alkenes. Control of facial selectivity by confinement and cation-π interactions
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Depending on the nature of the substituents on the stereogenic carbon atom, the ene reaction of singlet oxygen with several chiral alkenes by confinement within thionin-supported zeolite NaY, may exhibit significant changes on facial selectivity by comparison to their photooxygenation reaction in solution. It is proposed that, apart from the conformational consequences as a result of the alkene confinement within the zeolite cavities, a synergism between Na+-π interactions and singlet oxygen-Na+ interactions plays a significant role in the transition states of ene hydroperoxidation. Within NaY, the diastereoselectivity may significantly depend on the site selectivity, as probed through specific deuterium labelling of trisubstituted alkenes bearing a gem-dimethyl group. In certain cases, a remote stereogenic centre relative to the reacting double bond may induce enhanced diastereoselection and regioselectivity.
- Stratakis, Manolis,Raptis, Christos,Sofikiti, Nikoletta,Tsangarakis, Constantinos,Kosmas, Giannis,Zaravinos, Ioannis-Panagiotis,Kalaitzakis, Dimitris,Stavroulakis, Dimitris,Baskakis, Constantinos,Stathoulopoulou, Aggeliki
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p. 10623 - 10632
(2007/10/03)
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- HYDROAMINOMETHYLATION OF OLEFINS
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The present invention relates to a method comprising the step of contacting under hydroaminomethylation conditions, an olefin, an amine, a rhodium-phosphorous ligand, and synthesis gas (syngas). In particular, it has been discovered that, under some circumstances, a neutral rhodium-monodentate phosphite ligand is prescribed. The invention provides a simple way of making, in high yields and regiospecificity, a variety of products, including pharmacologically active products such as ibutilide, terfenadine, and fexofenadine, and derivatives thereof.
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Page/Page column 15-16
(2010/02/13)
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