Application of Ionic Liquid Halide Nucleophilicity for the Cleavage of Ethers:  A Green Protocol for the Regeneration of Phenols from Ethers

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Abstract

We have used the high nucleophilicity of bromide ion in the form of the ionic liquid, 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]), for the nucleophilic displacement of an alkyl group to regenerate a phenol from the corresponding aryl alkyl ether. Using 2-methoxynaphthalene (1) as a model compound, we found that the combination of ionic liquid [bmim][Br] and p-toluenesulfonic acid with warming effected demethylation in 14 h, affording the desired product 2-naphthol (2) in good yield (97%). Various other protic acids (MsOH, hydrochloric acid (35%), dilute sulfuric acid (50%)) could be used as a proton source in this demethylation reaction. Under the same conditions, cleavage of alkyl alkyl ether 2-(3-methoxypropyl)naphthalene yielded mixture of corresponding 2-(3-bromopropyl)naphthalene and 2-(3-hydroxypropyl)naphthalene. Dealkylation of various aryl alkyl ethers could also be achieved using significantly reduced (i.e., stoichiometric) amounts of concentrated hydrobromic acid (47%) in the ionic liquid. Both procedures afforded the desired products in moderate to good yield; however, cleavage of aryl alkyl cyclic ether, 2,3-dihydrobenzofuran, resulted in low yield of the desired product o-2-bromoethylphenol. The convenience of this method for ether cleavage and its effectiveness using only a moderate excess of hydrobromic acid make it attractive as a green chemical method.

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This article has been cited by 8 ACS Journal articles (5 most recent appear below).

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  Room-Temperature Ionic Liquids: Solvents for Synthesis and Catalysis. 2

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  • Room-Temperature Ionic Liquids: Solvents for Synthesis and Catalysis. 2

    Jason P. Hallett and Tom Welton
    Chemical Reviews2011 111 (5), 3508-3576
    Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links
• 

  Synergistic Effect of Two Solvents, tert-Alcohol and Ionic Liquid, in One Molecule in Nucleophilic Fluorination

  Sandip S. Shinde, Byoung Se Lee, and Dae Yoon Chi
  Organic Letters2008 10 (5), 733-735

  • Synergistic Effect of Two Solvents, tert-Alcohol and Ionic Liquid, in One Molecule in Nucleophilic Fluorination

    Sandip S. Shinde, Byoung Se Lee, and Dae Yoon Chi
    Organic Letters2008 10 (5), 733-735

    We have demonstrated the synergistic effect in nucleophilic fluorination when we combined two solventsionic liquid (IL) and tert-alcoholinto one molecule. Consequently, these functionalized ILs not only increase the nucleophilic reactivities of the ...

    Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links
• 

  Synthesis of Symmetrical Organic Carbonates via Significantly Enhanced Alkylation of Metal Carbonates with Alkyl Halides/Sulfonates in Ionic Liquid

  Yogesh R. Jorapur and Dae Yoon Chi
  The Journal of Organic Chemistry2005 70 (26), 10774-10777

  • Synthesis of Symmetrical Organic Carbonates via Significantly Enhanced Alkylation of Metal Carbonates with Alkyl Halides/Sulfonates in Ionic Liquid

    Yogesh R. Jorapur and Dae Yoon Chi
    The Journal of Organic Chemistry2005 70 (26), 10774-10777

    We report a new phosgene-free method for the synthesis of symmetrical organic carbonates via alkylation of metal carbonate with various alkyl halides and sulfonates in 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], as an ecofriendly ...

    Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links
• 

  A Theoretical Comparison of Lewis Acid vs Bronsted Acid Catalysis for n-Hexane → Propane + Propene

  Qingbin Li, Ken C. Hunter, and Allan L. L. East
  The Journal of Physical Chemistry A2005 109 (28), 6223-6231

  • A Theoretical Comparison of Lewis Acid vs Bronsted Acid Catalysis for n-Hexane → Propane + Propene

    Qingbin Li, Ken C. Hunter, and Allan L. L. East
    The Journal of Physical Chemistry A2005 109 (28), 6223-6231

    Cracking of an all-trans n-alkane, via idealized Lewis acid and Bronsted acid catalysis, was examined using density functional theory. Optimized geometries and transitions states were determined for catalyst−reactant complexes, using AlCl3 and HCl·AlCl3 ...

    Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links
• 

  Can the Absence of Solvation of Neutral Reagents by Ionic Liquids Be Responsible for the High Reactivity in Base-Assisted Intramolecular Nucleophilic Substitutions in These Solvents?

  Francesca D'Anna, Vincenzo Frenna, Renato Noto, Vitalba Pace, and Domenico Spinelli
  The Journal of Organic Chemistry2005 70 (7), 2828-2831

  • Can the Absence of Solvation of Neutral Reagents by Ionic Liquids Be Responsible for the High Reactivity in Base-Assisted Intramolecular Nucleophilic Substitutions in These Solvents?

    Francesca D'Anna, Vincenzo Frenna, Renato Noto, Vitalba Pace, and Domenico Spinelli
    The Journal of Organic Chemistry2005 70 (7), 2828-2831

    The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1a) into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (2a) induced by amines have been studied in two room-temperature ionic liquids (IL-1, [BMIM]...

    Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links

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