The Wolff rearrangement in radical cations

The mass spectrometric behavior of 1-phenyl-4,5,6,7-tetrahydrobenzotriazole and its seven membered analog is described. The principal fragmentation process of the molecular ions is loss of nitrogen. It was concluded from the results of deuterium labeling and accurate mass measurements that the subsequent fragmentation of the M-N2 ions proceeds via isomerization to the ring-contracted ketenimine ions by the Wolff rearrangement, in sharp contrast to the case of 1-phenylbenzotriazole. (auth.)