Dibenzo[a,o]phenanthro[3,4-s]pycene, a configurationally stable double helicene:: Synthesis and determination of its conformation by NMR and GIAO calculations

A double helicene formed by a pentahelicene and a heptahelicene with two rings in common was obtained by palladium-catalyzed cyclotrimerization of 3,4-didehydrophenanthrene and was characterized conformationally by NMR and GIAO calculations.