Scholl Reaction of ortho-Phenylene-Bridged Cyclic Pyrrole-Thiophene Hybrid Hexamer

Abstract

AbstractThe Scholl reaction of ortho-phenylene-bridged cyclic pyrrole-thiophene hybrid hexamer gave cyclophane-type [5]heterohelicene exclusively in 45% yield. The structure was unambiguously revealed by X-ray diffraction analysis. This helicenophane-type compound showed sharp absorption and fluorescence spectra, reflecting its rigid structure. The reaction path was analyzed on the basis of DFT calculations, and it was found that the formation of the [5]helicene-dimer is thermodynamically favored and further oxidation is prohibited due to the increased strain energy.