G. Domschke

Electron Spin Resonance and Electrochemical Studies of Some Mesoionic and Neutral 1,2,3,4‐Oxa‐ and ‐Thiatriazoles and Their Alkylation Products

Voltammetric studies of mesoionic 1,2,3,4‐oxa‐ and ‐thiatriazoles confirmed that the former may be reduced irreversibly at potentials between ‐1.19 and ‐1.73 V vs. ferrocene in acetonitrile at scan rates between 0.05 and 1000 mV s‐1, whereas the latter are reduced reversibly under the same conditions. The corresponding radical anions were examined by ESR spectroscopy. Cationic alkylation products of the above compounds showed different electrochemical behaviour depending on the character of the heterocyclic ring. 1,2,3,4‐Thiatriazolium ions were reduced reversibly. All coupling constants of the resulting neutral radicals were fully assigned using isotopic labelling. A cation with an 1,2,3,4‐oxatriazolium ring reacted by cleavaging of an exocyclic C—S bond on electron uptake. The resulting alkyl radical was spin‐trapped.

ELECTROCHEMICAL AND ELECTRON SPIN RESONANCE INVESTIGATIONS OF SOME 1,2,3-OXA- AND -THIADIAZOLES

Voltammetric studies on mesoionic 1,2,3‐oxa‐ and ‐thiadiazoles confirmed that the former may be reduced irreversibly at potentials between ‐1.48 and ‐2.12 V vs. Fc/Fc+ in acetonitrile at a scan rate of 200 mV s‐1, whereas the latter are reduced reversibly under the same conditions. The corresponding anion radicals were examined by ESR spectroscopy. Cationic alkylation products showed different electrochemical behaviour depending on the character of the heterocyclic ring. 1,2,3‐Thiadiazolium ions were reduced reversibly. All coupling constants of the resulting neutral radicals were fully assigned. 1,2,3‐Oxadiazolium ions were all reduced irreversibly.