Amidine dications as superelectrophiles

Corr, Michael J and Roydhouse, Mark D and Gibson, Kirsty F and Zhou, Sheng-Ze and Kennedy, Alan R and Murphy, John A (2009) Amidine dications as superelectrophiles. Journal of the American Chemical Society, 131 (49). pp. 17980-17985. ISSN 0002-7863

Abstract

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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