- Synthesis of Cyclic Enones by Allyl-Palladium-Catalyzed α,β-Dehydrogenation
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The use of allyl-palladium catalysis for the one-step α,β-dehydrogenation of ketones via their zinc enolates is reported. The optimized protocol utilizes commercially available Zn(TMP)2 as base and diethyl allyl phosphate as oxidant. Notably, this transformation operates under salt-free conditions and tolerates a diverse scope of cycloalkanones.
- Huang, David,Zhao, Yizhou,Newhouse, Timothy R.
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supporting information
p. 684 - 687
(2018/02/09)
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- Allyl-Palladium-Catalyzed Ketone Dehydrogenation Enables Telescoping with Enone α,β-Vicinal Difunctionalization
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The telescoping of allyl-palladium catalyzed ketone dehydrogenation with organocuprate conjugate addition chemistry allows for the introduction of aryl, heteroaryl, vinyl, acyl, methyl, and other functionalized alkyl groups chemoselectively to a wide variety of unactivated ketone compounds via their enone counterparts. The compatibility of the dehydrogenation conditions additionally allows for efficient trapping of the intermediate enolate with various electrophiles. The utility of this approach is demonstrated by comparison to several previously reported multistep sequences.
- Chen, Yifeng,Huang, David,Zhao, Yizhou,Newhouse, Timothy R.
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supporting information
p. 8258 - 8262
(2017/06/30)
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- Hydrolytic enantioselective protonation of cyclic dienyl esters and a β-diketone with chiral phase-transfer catalysts
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Hydrolytic enantioselective protonation of dienyl esters and a β-diketone catalyzed by phase-transfer catalysts are described. The latter reaction is the first example of an enantio-convergent retro-Claisen condensation. Corresponding various optically active α,β-unsaturated ketones having tertiary chiral centers adjacent to carbonyl groups were obtained in good to excellent yields and enantiomeric ratios (83-99%, up to 97.5:2.5 er).
- Yamamoto, Eiji,Gokuden, Daichi,Nagai, Ayano,Kamachi, Takashi,Yoshizawa, Kazunari,Hamasaki, Akiyuki,Ishida, Tamao,Tokunaga, Makoto
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supporting information
p. 6178 - 6181
(2013/02/25)
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- 3-Alkyl-p-menthan-3-ol derivatives: synthesis and evaluation of their physiological cooling activity
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Different 3-alkyl-p-methan-3-ol derivatives provide a strong physiological cooling effect with potential application as food and cosmetic additives. In order to investigate the influence of the chemical structure on the cooling sensation, the stereoselective syntheses of 29 different 3-alkyl-p-methan-3-ol derivatives were accomplished. All the compounds obtained are odorless and were evaluated by taste, considering two sensations: a cooling effect and bitterness. The results of this structure-activity relationship study highlight that compounds with a (1R,4S)-configuration are the isomers with the more intense cooling effect and lower bitterness. In addition, the structure of the 3-alkyl chain affected the latter properties. Increasing the chain length over two carbon atoms does not change the cooling power, but enhances the bitterness with the additional feature that the branched isomers are considerably more bitter than the linear ones. Overall, the 3-alkyl-p-menthan-3-ol isomers with the best quality in terms of high cooling power and low bitterness are (1R,4S)-3-(hydroxymethyl)-p-menthan-3-ol diastereoisomers (-)-38 and (-)-42.
- Fuganti, Claudio,Joulain, Daniel,Maggioni, Francesco,Malpezzi, Luciana,Serra, Stefano,Vecchione, Andrea
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body text
p. 2425 - 2437
(2009/04/06)
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- The Lewis acid-catalyzed intramolecular asymmetric ene reaction using a chiral α-cyanovinylic sulfoxide as an enophile
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A chiral α-cyanovinylic sulfoxide served as an efficient chiral enophile in a Lewis acid-catalyzed intramolecular ene reaction. Use of diethylaluminum chloride as a catalyst provided extremely high stereoselectivity in the ene reaction. The stereochemistry of the ene reaction products were determined by chemical correlation and the NMR spectral analysis. A mechanistic pathway for the asymmetric induction is presented on the basis of the stereochemical results obtained.
- Hiroi, Kunio,Umemura, Masayuki
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p. 1831 - 1840
(2007/10/02)
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- Lewis Acid-catalyzed Intramolecular Asymmetric Ene Reactions of Chiral Vinyl Sulfoxides
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A chiral α-cyanovinyl sulfoxide served as an efficient chiral enophile in a Lewis acid-catalyzed intramolecular ene reaction.Use of diethylaluminum chloride as a catalyst provided extremely high stereoselectivity in this ene reaction.Based on the stereochemical results obtained, a mechanistic pathway for this asymmetric induction is presented.
- Hiroi, Kunio,Umemura, Masayuki
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p. 3343 - 3346
(2007/10/02)
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- CATALYTIC ASYMMETRIC SYNTHESES. Part III. Asymmetric Hydrogenation of Piperitenone Catalysed by Chiral Ruthenium Hydrides: An Example of a Catalytic Kinetic Resolution.
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Piperitenone has been hydrogenated in the presence of chiral ruthenium catalysts to give piperitone, menthone and isomenthone.Starting from piperitone (42 percent e.e.) excellent selectivity (80 percent e.e.) was obtained with menthone.The mechanism of the reaction, a double asymmetric synthesis, is discussed with respect to kinetic resolution of piperitone as well as the effect of the chiral center in the substrate on the catalytic asymmetric induction.
- Le Maux, Paul,Massonneau, Viviane,Simonneaux, Gerard
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p. 1409 - 1412
(2007/10/02)
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- Sensitized Photooxygenation of Silyl Enol Ethers of Cyclic Ketones
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α,β-Unsaturated and α-hydroxy ketones are accessible in prototropic ene-reactions with singlet oxygen by sensitized photooxygenation of cyclic silyl enol ethers and subsequent reduction and solvolysis.In a competing silatropic ene-reaction α-silyloxyketones are formed.Formation of different products depends on ring size, configuration and substitution.At C-6 chirally substituted 2-cyclohexenones are synthesized for the first time by sensitized photooxygenation of chiral silyl enol ethers of optically active starting ketones.
- Friedrich, Edgar,Lutz, Werner
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p. 1245 - 1263
(2007/10/02)
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