Find in Library

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)-1<i>H</i>,1’<i>H</i>-[5,5’-bibenzimidazole]-4,4’,7,7’-tetrone (<b>CF₃-Bis-TEMPO-Vis</b>) 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 <b>CF₃-Bis-TEMPO-Vis</b>. 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 <b>Bis-TEMPO-Vis</b>.