Stable 3‐Imino‐2,3‐dihydroindazol‐1‐yl Radicals

Oxidation of 2-tert-butyl-3-(tert-butylamino)-2H-indazoles with lead(IV) oxide yields red, stable radicals, which can be distilled under high vacuum and recrystallized. They revert to their precursors on Pd-catalysed hydrogenation. Configuration and atomic distances were obtained by X-ray diffraction analysis. EPR hfc constants were assigned with the help of N-15 labeling and exchange of a phenyl hydrogen atom for a tert-butyl group. The X-ray and EPR results show that the novel radicals are to be considered as cyclic hydrazyl radicals, modified by delocalization of the unpaired electron involving the exocyclic imino group and the benzene ring.