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Stable 3‐Imino‐2,3‐dihydroindazol‐1‐yl Radicals
Author(s) -
Quast Helmut,
Philipp Gottfried,
Ross KarlHeinz,
Doht Ulrich M.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001659
Subject(s) - chemistry , radical , electron paramagnetic resonance , unpaired electron , benzene , medicinal chemistry , ring (chemistry) , hydrogen atom , electron delocalization , crystallography , delocalized electron , photochemistry , group (periodic table) , organic chemistry , nuclear magnetic resonance , physics
Oxidation of 2‐ tert ‐butyl‐3‐( tert ‐butylamino)‐2 H ‐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 15 N 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.