Amidine Dications as Superelectrophiles

Michael J. Corr, Mark D. Roydhouse, Kirsty F. Gibson, Sheng-ze Zhou, Alan R. Kennedy and John A. Murphy*
WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom
J. Am. Chem. Soc., 2009, 131 (49), pp 17980–17985
DOI: 10.1021/ja908191k
Publication Date (Web): November 16, 2009
Copyright © 2009 American Chemical Society

Abstract

Abstract Image

2-Dimethylalkylammonium pyridinium and 2-dimethylalkylammonium pyrimidinium ditriflate salts are very powerful methylating agents toward phosphorus (triphenylphosphine) and nitrogen (triethylamine) nucleophiles. In competition experiments with triethylamine as nucleophile, these N-methyl disalts are more reactive methylating agents than dimethyl sulfate. Reaction of the pyridinium dications with water as an oxygen nucleophile leads to attack at the 2-position of the heteroaromatic ring and displacement of an ammonium group; 2-hydroxypyridinium compounds are formed in the first instance, which are easily converted to 2-pyridones. Extending the scope of the reactions, a tricationic 2,6-bis(dimethylalkylammonium)pyridinium salt has also been prepared and characterized and its reactivity as a methylating agent assessed in comparison with that of the dications.

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History

  • Published In Issue December 16, 2009
  • Article ASAPNovember 16, 2009
  • Received: September 26, 2009

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