85716-73-0Relevant academic research and scientific papers
Multifunctional oxygen vacancies in WO3–x for catalytic alkylation of C–H by alcohols under red-light
Gu, Xianmo,Sun, Xichen,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
, p. 208 - 217 (2021/09/06)
Surface reaction kinetics and light absorption properties of a photocatalyst are essential demands for efficiently solar to chemical energy converting. In this study, plasmonic WO3–x was firstly applied to photocatalytic alkylation of arenes under red light irradiation. The oxygen vacancies, both on the surface and in the bulk of WO3–x, allow abundant free electrons to increase carrier densities and support its LSPR using low energy photons. The surface oxygen vacancies have more functions: they not only release surface tungsten sites which ensure the chemisorption of alcohols due to the coordianation ability but also promote the activation of alcohols via an efficient transport of the holes on the neighbouring O sites to chemisorption alcohol species. In brief, the bulk oxygen vacancies provide abundant charges and the surface vacancies promote the bond adsorption and activation abilities, which ensure the high efficiency of photocatalytic alkylation of C–H.
Br?nsted Acid and H-Bond Activation in Boronic Acid Catalysis
Zhang, Shaofei,Leb?uf, David,Moran, Joseph
supporting information, p. 9883 - 9888 (2020/06/10)
Boronic acid catalysis has emerged as a mild method for promoting a wide variety of reactions. It has been proposed that the mode of catalysis involves Lewis acid or covalent activation of hydroxyl groups by boron, but limited mechanistic evidence exists. In this work, representative boronic acid catalyzed reactions of alcohols and oximes have been reinvestigated. A series of control experiments with boronic and Br?nsted acids were interpreted along with correlations between their reactivity and their acidity measured by the Gutmann–Beckett method. Overall, it was concluded that the major modes of catalysis involve either dual H-bond catalysis or Br?nsted acid catalysis. Strong Br?nsted acids were shown to be generated in situ from covalent assembly of the boronic acids with hexafluoroisopropanol, explaining why the solvent had such a major impact on the reactivity. This new insight should guide the future development of boronic acid catalysis, where the diverse and solvent-specific nature of catalytic modes has been overlooked.
Two-component boronic acid catalysis for increased reactivity in challenging Friedel-Crafts alkylations with deactivated benzylic alcohols
Ang, Hwee Ting,Rygus, Jason P. G.,Hall, Dennis G.
supporting information, p. 6007 - 6014 (2019/06/24)
A general and efficient boronic acid catalyzed Friedel-Crafts alkylation of arenes with benzylic alcohols was previously developed for the construction of unsymmetrical diarylmethane products (X. Mo, J. Yakiwchuk, J. Dansereau, J. A. McCubbin and D. G. Hall, J. Am. Chem. Soc., 2015, 137, 9694). Highly electron-deficient benzylic alcohols, however, were ineffective coupling partners due to the increased difficulty of C-O bond ionization. Herein, we report the use of perfluoropinacol as an effective co-catalyst to improve the reactivity of a boronic acid catalyst in the Friedel-Crafts benzylations of electronically deactivated primary and secondary benzylic alcohols. According to spectroscopic studies, it is believed that perfluoropinacol condenses with the arylboronic acid catalyst to form a highly electrophilic and Lewis acidic boronic ester. This in situ formed species enables a more facile ionization of the benzylic alcohols likely through a mode of activation promoted by a Lewis acid assisted hydronium Br?nsted acid generated from the interactions of the transient boronic ester with hexafluoroisopropanol solvent and water.
Catalytic Friedel–Crafts Reactions of Highly Electronically Deactivated Benzylic Alcohols
Vukovi?, Vuk D.,Richmond, Edward,Wolf, Eléna,Moran, Joseph
supporting information, p. 3085 - 3089 (2017/03/14)
Highly electronically deactivated benzylic alcohols, including those with a CF3 group adjacent to the OH-bearing carbon, undergo dehydrative Friedel–Crafts reactions upon exposure to catalytic Br?nsted acid in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solvent. Titration and kinetic experiments support the involvement of higher order solvent/acid clusters in catalysis.
In situ activation of benzyl alcohols with XtalFluor-E: Formation of 1,1-diarylmethanes and 1,1,1-triarylmethanes through Friedel-Crafts benzylation
Desroches, Justine,Champagne, Pier Alexandre,Benhassine, Yasmine,Paquin, Jean-Franois
supporting information, p. 2243 - 2246 (2015/03/04)
The Friedel-Crafts benzylation of arenes using benzyl alcohols activated in situ with XtalFluor-E is described. A wide range of 1,1-diarylmethanes and 1,1,1-triarylmethanes were prepared under experimentally simple and mild conditions, without the need for a transition metal or a strong Lewis acid. Notably, the reactivity observed demonstrates the potential of XtalFluor-E to induce C-OH bond ionization and SN1 reactivity of benzylic alcohols. This journal is
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.
Iron oxide nanoparticles grown on carboxy-functionalized graphite: An efficient reusable catalyst for alkylation of arenes
Rajpara, Vikul,Banerjee, Subhash,Sereda, Grigoriy
experimental part, p. 2835 - 2840 (2010/10/04)
Here we report a simple procedure for the synthesis of a novel hybrid catalyst by growing iron oxide nanoparticles on carboxy-functionalized graphite. This hybrid catalyst demonstrated superior catalytic activity towards the alkylation of arenes with alkyl halides in contrast to commercial graphite or unsupported iron oxide nanoparticles in terms of yields and general applicability. The catalyst can be reused up to five times with a minimal loss of catalytic activity. Georg Thieme Verlag Stuttgart.
Palladium-catalyzed coupling reaction of 4-alkylnitrobenzenes with aryl bromides at their benzylic position
Inoh, Jun-Ichi,Satoh, Tetsuya,Pivsa-Art, Sommai,Miura, Masahiro,Nomura, Masakatsu
, p. 4673 - 4676 (2007/10/03)
4-Alkylnitrobenzenes effectively undergo coupling with aryl bromides at their benzylic position in the presence of a palladium catalyst and a base to give the corresponding mono- and/or di-arylated products in good yields.
SYNTHESIS OF SUBSTITUTED 2,4,5-TRIMETHYLDIPHENYLMETHANES
Pozdnyakovich, Yu. V.,Borodovitsyn, V. V.,Pozdnyakovich, S. A.,Shein, S. M.
, p. 353 - 359 (2007/10/02)
2,5-Dimethyldiphenylmethane and its 2'- and 4'-methyl, chloro, and nitro derivatives were obtained by the reaction of substituted benzyl chlorides with p-xylene in the presence of ferric chloride and zinc stearate.The yields of the 2,5-dimethyldiphenylmethanes depend on the nature of the substituent in the benzyl chloride and decrease with the substituents in the order NO2>Cl>H>CH3.The 2' and 4'-methyl, chloro, and aminoderivatives of 2,4,5-trimethyldiphenylmethane were synthesized by chloromethylation of the obtained diphenylmethanes with paraform in acetic acid in the presence of zinc chloride followed by reduction of the 2,5-dimethyl-4-chloromethyldiphenylmethanes with zinc in acetic acid.
