Isobutene arene alkylation

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... 

Metal vinyl and aryl complexes are two typical classes of products resulting from sp C—H bond activation from alkene and arene substrates, respectively. Bercaw and coworkers conducted a systematic study of the reactions between Cp 2ScR (R = alkyl or hydride) and various hydrocarbons and found that while ethylene underwent rapid polymerization with Cp 2ScMe, substituted alkenes, such as styrene and isobutene, were readily activated through cr-bond metathesis to result in scandium vinyl compounds (Scheme 8A). One... 

The mechanism involves the formation of a nucleophilic ferrate species from the iron(IIl) salt and ter/-butylmagnesium chloride. It undergoes oxidative addition to the aryl halide. Transmetalation with the Grignard reagent leads to an alkyliron compound. The latter is not preferentially prone to reductive elimination to form alkylated arenes. Instead, P-hydride elimination and subsequent reductive elimination of the hydrido-iron complex reforms the iron(-II) catalyst releasing isobutene and the defiinctionalized arene (Scheme 4-226). ... 

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