The reactions of 4-nitrobenzofuroxan with amines in DMSO; kinetic and equilibrium studies

Kinetic and equilibrium studies are reported for the reactions of six aliphatic amines with 4-nitrobenzofuroxan, 3, in dimethyl sulfoxide. Rapid reaction at the 5-position to yield σ-adducts is followed by slower formation of the thermodynamically more stable adducts at the 7-position. 1H NMR spectra are reported. The results are compared with those for reaction of the amines with 1,3,5-trinitrobenzene, 2. These reactions involve the initial formation of zwitterionic intermediates which transfer an amino proton to a second molecule of amine. It is found that the proton-transfer step is less likely to be rate determining in the reactions of 3 than of 2; this may be due to the lower steric requirements of 3.