Anodic oxidation of selenadiazoloquinolones in alkaline media

Newly synthesized derivatives of 6‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐h]quinoline variously substituted at position 7 (R = H, COOH, COCH3, CN, COOC2H5 and COOCH3) are established in strongly alkaline aqueous solutions (0.1 M NaOH; pH ∼ 13) as N(9)‐deprotonated structures, but in less alkaline solutions (0.001 M NaOH; pH ∼ 11) the N(9)‐protonated oxo tautomeric forms dominate. Upon their anodic oxidation in alkaline solutions, the selenadiazole ring is replaced, forming instead the paramagnetic species analogous to the ortho semiquinone radical anions as monitored by in situ EPR spectroscopy. The quantum chemical calculations for two representative selenadiazoloquinolones (R = H and COOH) and their anodic oxidation products presented are in agreement with experiments. Copyright © 2011 John Wiley & Sons, Ltd. Anodic oxidation of 6‐oxo‐6,9‐dihydro[1,2,5] selenadiazolo[3,4‐h]quinoline derivatives in aqueous alkaline media resulted in the replacement of selenadiazole ring, generating the paramagnetic species analogous to the ortho semiquinone radical anions as monitored by in situ EPR spectroscopy.