Synthesis and propelties of the first formazan substituted with a cyclopropenylio group in the 5-or 3-position are described. The latter isomer can adopt syn,s-cis or antis-trans configurations and can be oxidized to the corresponding cyclopropei ,iiotetrazolium salt.
INTRODUCTIONThe formazanide ion 1 and the tetrazolium ion 2 are part of a two-step redox system that is distinguished by an excellent charge stabilization within both Red and Ox form."] In order to be able to exploit this outstanding feature, we have explored several ways to introduce this redox system into organic