Pyrylium

Other names: pyranium

C₅H₅O⁺

25/50 common

The pyrylium cation is a six-membered aromatic heterocycle containing five carbon atoms and one positively charged oxygen atom. Though the parent pyrylium ion itself is highly reactive, its derivatives (especially those with phenyl substituents) form stable salts with non-nucleophilic counterions like tetrafluoroborate or perchlorate. These salts typically appear as brightly colored crystals, often yellow to red, and exhibit interesting photophysical properties. Pyrylium compounds serve as valuable synthetic intermediates, readily converting to other heterocycles including pyridines and pyrans. Their unique electronic properties have also found applications in photocatalysis and as chromophores in various optical materials.