Selenadiazolo[3,4-b]pyrazines: Synthesis from 3,4-Diamino-1,2,5-selenadiazole and Generation of Persistent Radical Anions

Previously unknown 3,4‐diamino‐1,2,5‐selenadiazole (6) was prepared by hydrolysis of [1,2,5]selenadiazolo[3,4‐c][1,2,5]selenadiazole (7b) and used in synthesis of novel 1,2,5‐selenadiazolo[3,4‐b]pyrazines by the Koerner–Hinsberg reaction covering the parent compound 4 and its substituted derivatives 5a–g. The compounds synthesized were characterized by solution and solid‐state ⁷⁷Se NMR, and 6, 5‐Ph and 5,6‐Me₂[1,2,5]selenadiazolo[3,4‐b]pyrazines (5a, g, respectively) by X‐ray diffraction. Electrochemical reduction of 5,6‐R₂[1,2,5]selenadiazolo[3,4‐b]pyrazines 5c, g (R = Ph, Me) into novel persistent radical anions (RAs) was studied by cyclic voltammetry and the RAs [5c]^– and [5g]^– were characterized by EPR spectroscopy combined with DFT calculations.