1,2-Phenylene-Incorporated Smallest Expanded Calix[4]pyrrole via One-Step Synthesis of Tetrapyrrane: A Fluorescent Host for Fluoride Ion

J Org Chem. 2021 Aug 6;86(15):10536-10543. doi: 10.1021/acs.joc.1c01179. Epub 2021 Jul 28.

Abstract

Synthesis of tetrapyrrane 8 from acetone and pyrrole via one-step condensation was achieved for the first time along with a much-improved yield of the tripyrrane 9. Diborylation of the tetrapyrrane and subsequent "1 + 1" cyclocoupling with 1,2-diiodobenzene following the Suzuki protocol generated novel o-phenylene incorporated macrocycle belonging to the smallest meso-expanded calix[4]pyrrole family. The latter macrocycle displays exclusive turn-on fluorescence sensing of fluoride ion upon complexation via a unique partial cone conformation supported by DFT analysis in acetonitrile solvent.