- Nitrosonium salts, NO+X- (X = B(3,5-diCF 3Ph)4- or PW12O40 3-), as electrophilic catalysts for alkene activation in arene alkylation and dimerization reactions
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It has been found that in apolar reaction media the nitrosonium cation (NO+) activated alkenes under mild conditions toward electrophilic substitution of arene substrates to yield the alkylated arene with Markovnikov orientation. In the absence of arenes the alkenes react with themselves to yield a mixture of dimeric alkenes. The nitrosonium cation can be dissolved in the reaction medium by using the tetrakis-(bis-(3,5-trifluromethyl)phenyl) borate anion, where upon the reactions occur effectively at 30 °C. Alternatively an insoluble, heterogeneous catalyst was prepared so as to yield a NO+ cation with a polyoxometalate (PW12O403-) anion. This catalyst was generally more effective and selective toward a broader range of substrates at 70 °C. Copyright
- Khenkin, Alexander M.,Neumann, Ronny
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supporting information; scheme or table
p. 11876 - 11877
(2009/02/05)
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- ALKYLATION NON CONVENTIONNELLE DE FRIEDEL ET CRAFTS DES AROMATIQUES PAR LES ISO ET CYCLOALCANES INDUITE PAR LES CHLORURES-SELECTIVITE ET OPTIMISATION
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Friedel-Crafts alkylation of benzene by C5-C8 isoalkanes induced by tert-butyl chloride affords good yields in the presence of small amounts of AlCl3.The isomeric alkylbenzenes prepared by hydride transfer are similar to those obtained by direct alkylation from the corresponding equivalent alcohols and chlorides.The kinetic tertiary alkyl benzene rearranges to a more stable secondary isomer ; the formation of isomers discussed.Fragmentation of isoalkanes (when any) is very small except with isooctane which gives only a tert-butyl-cation.The reaction may be extended to toluene, chlorobenzene and dichlorobenzene with no major change in selectivity i.e. trans vs direct alkylation.An optimization of the reaction using dichlorobenzene increases significantly conversion and selectivity in trans-alkylation product and stresses the importance of low temperature (ca. 40 deg C) and small amounts of catalyst.
- Iraqi, A.,Gallo, R.,Phan Tan Luu, R.
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p. 548 - 554
(2007/10/02)
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- Photochemical Reaction of 1,4-Naphthalenedicarbonitrile with Alkylbenzenes and Bibenzyls
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The photochemical reaction of 1,4-naphthalenedicarbonitrile with some alkylbenzenes and bibenzyls has been examined.A unitary mechanistic picture is formulated on the basis of product study, deuteration experiments, and fluorescence and reaction quantum yield measurements.Proton transfer within the singlet radical ion pair followed by in-cage cycloaddition of the two radicals yields stereoselectively 5,11-methanodibenzo cyclooctene derivatives (8).Reaction of benzyl radicals (formed by protolysis or, for radical cations having no benzylic proton, by C-C bond cleavage) with unprotonated NDN.- leads, again stereoselectively, to 2-benzyl-1,2-dihydronaphtalenes (9).Escape of the donor radical cation and following C-H or C-C bond cleavage leads to a different product, thus, benzyl radicals are trapped by NDN to yield substitution products (11) or recombine.Benzyl cations are trapped by nucleophiles.
- Albini, Angelo,Fasani, Elisa,Mella, Mariella
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p. 4119 - 4125
(2007/10/02)
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- Alkyl Metal Asymmetric Reduction. 12. Optically Active Phenylalkanes from Organoaluminum Derivatives and Aliphatic Ketones
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The reaction of β-branched alkylaluminum dichloride with some aliphatic ketones has been studied in various solvents at room temperature.In benzene, the organoaluminum derivative rapidly reduces the ketone with formation of the alkoxyaluminum dichloride, which slowly alkylates the benzene to the corresponding phenylalkane.When optically active (2-methylbutyl)aluminum dichloride is used, both the carbinol from hydrolysis of the alkoxy aluminum species and the phenylalkane are optically active and of opposite absolute configuration.The overall results are also interpreted on the basis of previous findings, and a mechanism that accounts f or the formation of the optically active phenylalkanes is presented.
- Giacomelli, Giampaolo,Lardicci, Luciano
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p. 4335 - 4337
(2007/10/02)
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