Ethylammonium Nitrate (EAN)/Tf₂O and EAN/TFAA: Ionic Liquid Based Systems for Aromatic Nitration

Abstract

Acting as in situ sources of triflyl nitrate (TfONO(2)) and trifluoroacetyl nitrate (CF(3)COONO(2)), the EAN/Tf(2)O and EAN/TFAA systems, generated via metathesis in the readily available ethylammonium nitrate (EAN) ionic liquid as solvent, are powerful electrophilic nitrating reagents for a wide variety of aromatic and heteroaromatic compounds. Comparative nitration experiments indicate that EAN/Tf(2)O is superior to EAN/TFAA for nitration of strongly deactivated systems. Both systems exhibit low substrate selectivity (K(T)/K(B) = 5-10) in between values reported for covalent nitrates and preformed nitronium salts.