The uncatalysed formation
of stable 1 : 1 Meisenheimer complexes between primary, secondary and tertiary
aromatic amines and 4,6-dinitrobenzofurazan 1-oxide has been investigated. The
thermodynamic product is derived from reaction through the aromatic carbon para
or, if this position is substituted, ortho to the amino group of the aromatic
amine. The complexes are stable to acid but react in aqueous potassium hydrogen
carbonate solution or with aliphatic or aromatic amines to give crystalline
salts of the complexes. In the presence of 1,4-diazabicyclo[2.2.2]octane,
aniline reacts with 4,6-dinitrobenzofurazan 1-oxide to give an unstable
nitrogen-bonded complex which is slowly converted into the carbon-bonded
complex. The scope of the complexation reaction has been investigated and some
of the mechanistic implications of the results are discussed.