- Electrophilicities of symmetrically substituted 1,3-diarylallyl cations
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Kinetics of the reactions of nine symmetrically substituted 1,3-diarylallyl cations with different nucleophiles were studied photometrically in dichloromethane, acetonitrile, and DMSO solutions. The second-order rate constants k2 were found to follow the correlation log k2 = sN(N + E). The electrophilicity parameters E of the title cations were derived, using the known values of sN and N of the nucleophilic reaction partners, and compared with the electrophilicities of analogously substituted benzhydrylium ions. Good linear correlations were found between the electrophilicities E and the quantum chemically calculated gas-phase methyl anion affinities of the allyl cations and the σ+ constants of the substituents X.
- Troshin, Konstantin,Schindele, Claus,Mayr, Herbert
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p. 9391 - 9408
(2012/01/06)
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- Phenyl group acceleration of [1,4] carbon-to-oxygen silicon-mediated elimination-rearrangement in β-silyl sulfones. Synthesis of O-silylated cinnamyl alcohols
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A very fast [1,4] carbon-to-oxygen silicon migration-rearrangement leading to O-silylated cinnamyl alcohols occurs when the carbanion generated from sulfone 1 is reacted with carbonyl compounds. The mandatory role of the adjacent phenyl ring in this process is demonstrated when compared to the behaviour of the corresponding unsubstituted sulfone 3.
- Menichetti,Stirling
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- Carbon-carbon bond formation by reactions of allylic alcohol with enoxysilane in the presence of Ir-complex
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Substitution of allylic alcohols to form a carbon-carbon bond is accomplished by a simple reaction of the allylic alcohol itself with an enoxysilane, catalyzed by [Ir(cod)(PPh3)2]X which is activated by H2 molecule. The anion part X of the complexes plays an important role to enhance the rate and product yields of the reactions. The efficacy of the catalyst increases with switching X in the order of PF6-4--.
- Matsuda, Isamu,Wakamatsu, Shogo,Komori, Ken-Ichi,Makino, Tatsuya,Itoh, Kenji
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p. 1043 - 1046
(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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- The synthesis of 6,6,6-2H3-2E-hexenal
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6,6,6-2H3-2E-Hexenal, leaf-aldehyde, has been synthesised in 45% yield and 99.3% purity by reaction of 3,3,3-2H3-n-propyl magnesium bromide with an ethereal solution of 3-trimethylsiloxy-2-propenal (3) prepared in situ. This new one pot procedure alleviates the need to isolate (3) and should prove useful in the synthesis of other E-α,β-unsaturated aldehydes.
- Fielder,Rowan
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p. 199 - 204
(2007/10/02)
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- Facile 1,4-Silyl Rearrangement with Concomitant Loss of a Benzenesulfonyl Group: One-Pot Synthesis of Allyloxysilanes
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In contrast to the thermal stability of the oxido anions 7, facile eliminative rearrangement has been shown to occur in the case of the oxido anions 2 which possess an aryl substituent on the carbon atom bearing the trimethylsilyl group.Thus, the one-pot
- Ochiai, Masahito,Sumi, Kenzo,Fujita, Eiichi
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p. 3686 - 3689
(2007/10/02)
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