Amidine dications as superelectrophiles.
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.
Corr
Michael J
MJ
WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.
Roydhouse
Mark D
MD
Gibson
Kirsty F
KF
Zhou
Sheng-Ze
SZ
Kennedy
Alan R
AR
Murphy
John A
JA
D000578:Amidines / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D004563:Electrochemistry; D015394:Molecular Structure
D000578:Amidines; D002412:Cations