Release of Nitrosating Species in the Course of Reduction of Benzo-1,2,3,4-tetrazine 1,3-Dioxides

The reduction of benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) 1 with Na2S2O4 or SnCl2 is suggested to proceed via intermediate N-nitrosobenzotriazoles 3 to afford benzotriazoles 2. The 15N-labeling experiments exhibit that the N-3 atom of the tetrazine ring is incorporated into the nitroso group of 3 that is ultimately released into solution. It is possible that the biological activity of BTDOs is due to their ability to release nitrosating species, i.e., N-nitrosotriazol 3 or HNO2, in the course of reduction.