Aromatic alkylation by gaseous Me3C+ ions. Kinetic role of deprotonation of intermediate arenium ions
The alkylation of m-xylene by Me3C+ ions has been studied in the gas phase with the aim of assessing the kinetic role of proton transfer from intermediate arenium ions. Hydrogen kinetic isotope effects (KIEs) emerging from the reaction of m-xylene-4-d and of m-xylene/m-xylene-d10 mixtures have been exploited as mechanistic probes. The Me3C substitution at the 4-position displays a base-strength-dependent KIE related to rate-determining deprotonation of arenium intermediates. The Me3C+ reaction at the 5-position is instead characterized by a base-independent KIE due to 1,2-hydrogen shift to form a highly stable isomeric arenium ion. When the latter species originates from m-xylene-4-d, its neutralization involves an intramolecular competition of proton vs deuteron abstraction, manifesting a net primary KIE. Factors affecting its magnitude and base-strength dependence are discussed.
Nickel-catalyzed Kumada cross-coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates
We report a Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.
Joshi-Pangu, Amruta,Wang, Chao-Yuan,Biscoe, Mark R.
supporting information; experimental part
p. 8478 - 8481
(2011/06/25)
Preparation of 5-tert-butyl-metaxylene using a solid active clay catalyst
Alkylation of metaxylene with isobutylene using a solid active clay catalyst produces 5-tert-butyl-metaxylene with high isomer selectivity with respect to 4-tert-butyl-metaxylene. The process is controlled to extend catalyst life and significantly reduce environmentally unfriendly waste.
-
Page 4
(2008/06/13)
Perfluorooctanesulfonic acid catalyzed Friedel-Crafts alkylation with alkyl halides
A new procedure to prepare superacid perfluorooctanesulfonic acid (POSA) is reported. POSA catalyzed Friedel-Crafts alkylation of aromatic compounds with alkyl halides in liquid-phase reactions. Alkylation gave higher total yields than the corresponding reactions with Nafion-H, without the need of any complex decomposition or work-up. The reactions do not need to be carried out under absolutely anhydrous condition. The catalyst POSA can be easily separated from the reaction mixture and reused or recovered. The reactivity of the alkylation reagents and the mechanism of the reaction are discussed.
Fu,He,Lei,Luo
p. 1273 - 1279
(2007/10/02)
More Articles about upstream products of 14411-55-3