Cramping an Alkyl Group by Rigid Macrocyclic Framework

Abstract

An anthracene–acetylene cyclic dimer with an intra-annular ethyl group was synthesized as a sterically congested π-conjugated compound by cyclization with Sonogashira coupling. The ethyl group was conformationally cramped by the rigid macrocyclic framework because of the severe steric interactions, as revealed by ¹H NMR spectroscopy and DFT calculation.