Acylation of dipyrromethanes at the α and β positions and further development of fluorescent Zn2+ probes

Abstract The acylation of 5-aryl dipyrromethanes afforded products with interestingly rich substitution modes, i.e. , α- and β-monoacylated (modes a and b ), and α, α′-, α, β′- and β, β′-diacylated (modes c – e ). Especially, the β- and β, β′-acylation modes are unprecedented. And most of these products can be synthesized at a gram scale. The anisoyl substituted 5-(4-cyanophenyl) dipyrromethanes ( 1a – 1e ) were oxidized with DDQ. Thus, 1a and 1b afforded the corresponding dipyrrins 1a-DPR , and 1b-DPR . More interestingly, the diacylated ones 1c – 1e could not be oxidized by DDQ. Instead, 1c-OH – 1e-OH were obtained with a hydroxyl group attached to the 5-position. 1a-DPR – 1e-OH were further developed as fluorescence turn-on Zn 2+ probes. 1d-OH showed the highest sensitivity, with a detection limit of 1.5 × 10 −8  M, and it was successfully applied in Zn 2+ imaging in Hela cells. Furthermore, single crystals of two Zn 2+ complexes were obtained and analyzed by X-ray diffraction.