CF₃-Bis-TEMPO-Vis : new visible light active bis-benzimidazolequinone alkoxyamine

Kielty, Patrick, Farràs, Pau, Smith, Dennis A. and Aldabbagh, Fawaz (2021) CF₃-Bis-TEMPO-Vis : new visible light active bis-benzimidazolequinone alkoxyamine. Molbank, 2021(4), M1300. ISSN (online) 1422-8599


Alkoxyamines of TEMPO usually dissociate thermally at >100 °C; however, room temperature homolysis, activated by visible light, occurs with benzimidazolequinone derivatives. 1,1’-Dimethyl-2,2’-bis{[(2,2,6,6-tetramethylpiperidin-1-yl)oxy]methyl}-6-(trifluoromethyl)-1H,1’H-[5,5’-bibenzimidazole]-4,4’,7,7’-tetrone (CF₃-Bis-TEMPO-Vis) is prepared in a 59% yield through NBS/H₂SO₄ oxidative demethylations of the dimethoxybenzimidazole-benzimidazolequinone precursor with aqueous work up. The alternative basic work up in air gave the epoxide derivative of CF₃-Bis-TEMPO-Vis. Unlike the latter CF₃-epoxide, both alkoxyamine residues are labile under green light (470−600 nm), and the rate of TEMPO release is three times slower than Bis-TEMPO-Vis.

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