Synthesis and Structural Elucidation of Diversely Functionalized 5,10-Diaza[5]Helicenes

Diversely functionalized diaza[5]­helicenes have been
synthesized
starting from 6,9-dichloro-5,10-diaza[5]­helicene, which was prepared
from a readily available quinoline building block via Wittig reaction
followed by photochemical electrocyclization. The helicene skeleton
was substituted by a variety of O-, S-, N-, and C-centered nucleophiles
using nucleophilic aromatic substitution reactions and palladium-catalyzed
reactions like Suzuki coupling and Buchwald–Hartwig aminations.
We have determined, using X-ray single-crystal diffraction, the crystal
structures of the chloro- and methoxy-substituted diaza[5]­helicenes.
A resolution strategy based on diastereomeric separation by substitution
of the dichloro derivative with a chiral amine has been shown.