50796-62-8Relevant articles and documents
Development of highly efficient Friedel-Crafts alkylations with alcohols using heterogeneous catalysts under continuous-flow conditions
Kobayashi, Shū,Koumura, Nagatoshi,Masuda, Koichiro,Okamoto, Yukiko,Onozawa, Shun-Ya
, p. 24424 - 24428 (2021/07/29)
The development of Friedel-Crafts alkylations with alcohols under continuous-flow conditions using heterogeneous catalysts is reported. The reactivities and durabilities of the examined catalysts were systematically investigated, which showed that montmorillonite clay is the best catalyst for these reactions. A high turnover frequency of 9.0 × 102h?1was recorded under continuous-flow conditions, and the continuous operation was successfully maintained over one week.
Unsymmetrical diarylmethanes by ferroceniumboronic acid catalyzed direct friedel-crafts reactions with deactivated benzylic alcohols: Enhanced reactivity due to ion-pairing effects
Mo, Xiaobin,Yakiwchuk, Joshua,Dansereau, Julien,Adam McCubbin,Hall, Dennis G.
supporting information, p. 9694 - 9703 (2015/08/18)
The development of general and more atom-economical catalytic processes for Friedel-Crafts alkylations of unactivated arenes is an important objective of interest for the production of pharmaceuticals and commodity chemicals. Ferroceniumboronic acid hexafluoroantimonate salt (1) was identified as a superior air- and moisture-tolerant catalyst for direct Friedel-Crafts alkylations of a variety of slightly activated and neutral arenes with stable and readily available primary and secondary benzylic alcohols. Compared to the use of classical metal-catalyzed alkylations with toxic benzylic halides, this methodology employs exceptionally mild conditions to provide a wide variety of unsymmetrical diarylmethanes and other 1,1-diarylalkane products in high yield with good to high regioselectivity. The optimal method, using the bench-stable ferroceniumboronic acid salt 1 in hexafluoroisopropanol as cosolvent, displays a broader scope compared to previously reported catalysts for similar Friedel-Crafts reactions of benzylic alcohols, including other boronic acids such as 2,3,4,5-tetrafluorophenylboronic acid. The efficacy of the new boronic acid catalyst was confirmed by its ability to activate primary benzylic alcohols functionalized with destabilizing electron-withdrawing groups like halides, carboxyesters, and nitro substituents. Arene benzylation was demonstrated on a gram scale at up to 1 M concentration with catalyst recovery. Mechanistic studies point toward the importance of the ionic nature of the catalyst and suggest that factors other than the Lewis acidity (pKa) of the boronic acid are at play. A SN1 mechanism is proposed where ion exchange within the initial boronate anion affords a more reactive carbocation paired with the non-nucleophilic hexafluoroantimonate counteranion.
High catalytic efficiency of nanostructured molybdenum trioxide in the benzylation of arenes and an investigation of the reaction mechanism
Wang, Feng,Ueda, Wataru
experimental part, p. 742 - 753 (2009/10/01)
The synthesis and characterization of nanostructured MoO3 with a thickness of about 30 nm and a width of about 450 nm are reported. The composition formula of the MP (precipitation method) precursor was estimated to be [(NH4)2O]0.169·MoO 3· (H2O)0.239. The calcination of the precursor in air afforded nanostructured pellets of the α-MoO3 phase. The nano-structured MoO3 catalyst exhibited high efficiency in catalyzing the benzylation of various arenes with substituted benzyl alcohols, which were strikingly different to common bulk MoO3. Most reactions offered >99% conversion and >99% selectivity to monoalkylated compounds. MoO3 is a typical acid catalyst. However, the benzylation reaction over nanostructured MoO3 does not belong to the acid-catalyzed type or defect site-catalyzed type, since the catalyst has no acidity and defect site on surface. Characterization with thermal, spectroscopic, and electronic techniques reveal that the catalyst contains fully oxygen-coordinated MoO 6 octahedrons on the surface but partially reduced species (Mo 5+) within the bulk phase. The terminal oxygen atoms of Mo=O bonds on the (010) basal plane resemble oxygen anion radicals and act as active sites for the adsorption and activation of benzyl alcohols by electrophilic attack. Such sites are indispensable for catalytic reactions since the blocking of these sites by electron acceptors, such as tetracyanoethylene (TCNE), can greatly decrease catalytic activity. This work represents a successful example of combining a heterogeneous catalysis study with nanomaterial synthesis.
