Palladium-Catalyzed Cyclization of a Pyryne Precursor to Higher Pyrenylenes.

Abstract

The palladium catalyzed cyclotrimerization of ortho-silylaryl triflates as aryne precursors is meanwhile an established method to synthesize polycyclic aromatic hydrocarbons (PAHs) with triphenylene cores. During the palladium-catalyzed reaction of a pyrene with an o-silylaryl triflate moiety in the K-region, besides the expected trimer higher homologues with central eight- and ten-membered rings (the pyrenylenes) were found and a protocol developed to isolate all members of this series. This unprecedented new class of PAHs was fully investigated by all means, including X-ray diffraction of single-crystals, UV/vis and fluorescence spectroscopy and theoretical calculations. Furthermore, supported by density-functional theory (DFT) calculations, a mechanism of all higher cyclooligomers is proposed.