Redox Active Quinoidal 1,2,4-Benzotriazines
Date
2018ISSN
0022-3263Source
The Journal of Organic ChemistryVolume
83Issue
16Pages
9391-9402Google Scholar check
Metadata
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Modifying the para-quinonimine 1,3-diphenyl-1,2,4-benzotriazin-7(1H)-one (2a) (E1/2–1/0 −1.20 V), by replacing the N1-phenyl by pentafluorophenyl, the C3-phenyl by trifluoromethyl, or the C7 carbonyl by ylidenemalononitrile, led to improved electron affinities as determined by cyclic voltammetry and computational studies. Combining structural changes further improved electron accepting abilities: the most electron deficient analogues (E1/2–1/0 ∼ −0.65 V) involved combining the ylidenemalononitrile groups at C7 with the trifluoromethyl groups at C3. 1,2,5-Thiadiazolo fusion at C5–C6 did not affect the redox behavior but did enhance the UV–vis absorption profile. During the synthesis of the thiadiazolo analogues, 1,4-thiazino-fused analogues 6 were obtained in low yield, which thermally ring contract to the triazafluoranthenones 7. Compounds are fully characterized, and X-ray data are provided for selected analogues.