Synthesis of Helquats Based on Phenanthridinium Units: Four-Step Procedure to Novel Extended Helical Dications
2015
Abstract
Three novel helical dications (helquats) containing phenanthridinium units have been synthesized from 6-(pyridin-2-ylethyn-yl)phenanthridine as a common precursor prepared by Sonogashira coupling of phenanthridin-6-yl triflate with 2-ethynylpyridine. Bisquaternization of the common precursor followed by rhodium-catalyzed [2+2+2] cycloisomerization led to the title helical dicationic scaffolds.
The connectivity and spatial arrangement of the three target helquats were unambiguously established by X-ray crystal structure analysis.