Syntheses of mono- and diacylated bipyrroles with rich substitution modes and development of a prodigiosin derivative as a fluorescent Zn(ii) probe

Abstract

The acylation of 2,2′-bipyrrole with pentafluorobenzoyl chloride in the presence of AlCl₃ afforded six acylated products with rich α-, β-, β₁-, α,α′-, α,β′-, and α,β₁′-substitution modes for 1–6, respectively. Then, the α,α′-diacylated compound 4 was used to synthesize a prodigiosin derivative 9, which provides an alternative method for the syntheses of prodigiosin derivatives. Crystal structures of 1, 4 and 9 show interesting supramolecular dimers formed by multiple hydrogen bonds, O⋯π interactions, as well as π⋯π interactions. Interestingly, 9 shows fluorescence turn-on probing behavior towards Zn²⁺ both in DMF and in DMF–HEPES, with high sensitivity and selectivity. The detection limit for Zn²⁺ in DMF was calculated to be 1.1 × 10⁻⁸ M.