Conversion of Phenyl-Substituted Cyclopentadienes to Pyrylium Cations

Phenyl-substituted cyclopentadienes are proved to form phenylated pyrylium cations in the presence of silver(I) perchlorate by insertion of an oxygen atom into the cyclopentadiene-ring. Three phenylated pyrylium compounds, [(Ph5C5O+)(ClO4-)]2(CH2Cl2) (1), Ag(ClO4)(H2O)(Ph4HC5O+) (ClO4-) (2), and (Ph3H2C5O+)(ClO4-) (3) have been synthesized and characterized. A possible reaction pathway and formation mechanism of the pyrylium cation are proposed and discussed.