- Mn-Enabled Radical-Based Alkyl-Alkyl Cross-Coupling Reaction from 4-Alkyl-1,4-dihydropyridines
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Highly efficient alkylation of β-chloro ketones and their derivatives was achieved by means of domino dehydrochlorination/Mn-enabled radical-based alkyl-alkyl cross-coupling reaction. In situ-generated α,β-unsaturated ketones and their analogues were identified as the reaction intermediates. Known bioactive compounds, such as melperone and azaperone, could be easily prepared from β-chloropropiophenone in two steps.
- Wang, Jie,Pang, Yu-Bo,Tao, Na,Zeng, Run-Sheng,Zhao, Yingsheng
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p. 15315 - 15322
(2019/11/19)
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- Catalytic Carbocation Generation Enabled by the Mesolytic Cleavage of Alkoxyamine Radical Cations
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A new catalytic method is described to access carbocation intermediates via the mesolytic cleavage of alkoxyamine radical cations. In this process, electron transfer between an excited state oxidant and a TEMPO-derived alkoxyamine substrate gives rise to a radical cation with a remarkably weak C?O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO.as well as a reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles. Notably, this process occurs under neutral conditions and at comparatively mild potentials, enabling catalytic cation generation in the presence of both acid sensitive and easily oxidized nucleophilic partners.
- Zhu, Qilei,Gentry, Emily C.,Knowles, Robert R.
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p. 9969 - 9973
(2016/08/16)
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- Asymmetric Conjugate Addition of Organoboron Reagents to Common Enones Using Copper Catalysts
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Copper complexes of phosphoramidites efficiently catalyzed asymmetric addition of arylboron reagents to acyclic enones. Importantly, rare 1,4-insertion of arylcopper(I) was identified which led directly to O-bound copper enolates. The new mechanism is fundamentally different from classical oxidative addition/reductive elimination of organocopper(I) on enones.
- Wu, Chunlin,Yue, Guizhou,Nielsen, Christian Duc-Trieu,Xu, Kai,Hirao, Hajime,Zhou, Jianrong
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supporting information
p. 742 - 745
(2016/02/05)
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- Pd-catalyzed asymmetric hydrogenation of C=C bond of α,β- unsaturated ketones
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Homogenous palladium-catalyzed asymmetric hydrogenation of C=C double bond of ,-unsaturated ketones has been -developed by using palladium(II) trifluoroacetate/(S)-7,7-bis-[di(4-methoxyphenyl]phosphino)-1,1-spirobiindane complex [Pd(OCOCF3)2-(S)-An-SDP] as the catalyst under ambient hydrogen pressure and room temperature with up to 89% ee. Georg Thieme Verlag Stuttgart · New York.
- Wang, Duo-Sheng,Wang, Da-Wei,Zhou, Yong-Gui
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p. 947 - 950
(2011/06/17)
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- Chiral Lewis acid catalyzed enantioselective conjugate radical additions to α,β-unsaturated 2-pyridyl ketones
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We have investigated the utility of a pyridine-based achiral template in enantioselective conjugate radical additions. Georg Thieme Verlag Stuttgart.
- Sibi, Mukund P.,Yang, Yong-Hua
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- Chiral diselenide ligands for the asymmetric copper-catalyzed conjugate addition of Grignard reagents to enones
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The copper-catalyzed conjugate addition of Grignard reagents to enones in the presence of chiral diselenide oxazoline ligands has been studied and found to provide good yields and useful levels of asymmetric induction.
- Braga, Antonio L,Silva, Sandra J.N,Lüdtke, Diogo S,Drekener, Roberta L,Silveira, Claudio C,Rocha, Joao B.T,Wessjohann, Ludger A
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p. 7329 - 7331
(2007/10/03)
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- Tandem addition β-lithiation - Alkylation sequence on α,β-unsaturated aldehydes
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A tandem reaction between (E)-cinnamaldehyde, 1a, and phenyllithium affording β-substituted dihydrochalcones was recently reported. NMR spectroscopic studies on the reaction mixture, as well as isotopic exchange reactions and trapping of two intermediates, provide clues on the several mechanistic steps of this new reaction. Extended studies revealed that β-alkyl-substituted α,β-unsaturated aldehydes and aliphatic lithium reagents did not afford good yields of the tandem reaction products, while aromatic lithium reagents gave good results. The aggregation features of the aryllithium reagents and the extended charged delocalization effects are considered to promote β-selectivity. This approach provides a convenient route for the synthesis of a wide variety of β-alkyl-substituted dihydrochalcones.
- Nudelman,Garcia
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p. 1387 - 1394
(2007/10/03)
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- Mechanism of the Grignard Adddition Reaction. XVI. Homolytic and Concerted Mechanisms in the Reaction of α,β-Unsatureted Carbonyl Compounds with Grignard Reagents
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Kinetic measurements have shown that the addition of Grignard reagents to α,β-unsaturated carbonyl compounds takes place either by a concerted mechanism or by a homolytic mechanism.Phenylmagnesium bromide, which is incapable of homolysis, reacts rapidly in a 1,4-fashion if an s-cis conformation exists between the C=C and the C=O bonds, but only 1,2-addition takes place if the conformation is s-trans.tert-Butylmagnesium bromide is unsuited to the concerted reaction, but 1,4-addition takes place via homolysis.Primary and secondary Grignard reagents, like phenyl, react rapidly in a concerted manner with s-cis substrates, but unlike phenyl, these Grignard reagents may, with s-trans substrates, produce some 1,4-adduct via the homolytic mechanism.
- Holm, Torkil
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p. 925 - 929
(2007/10/02)
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- Reactions of Carbonyl Compounds with Grignard Reagents in the Presence of Cerium Chloride
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The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable supression of side reactions, particularly enolization.Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.
- Imamoto, Tsuneo,Takiyama, Noboyuki,Nakamura, Kimikazu,Hatajima, Toshihiko,Kamiya, Yasuo
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p. 4392 - 4398
(2007/10/02)
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