Oxidation of some aromatic hydrocarbons by cerium(IV) trifluoroacetate

Abstract

The preparation of cerium(IV) trifluoroacetate, and its reactions with some benzenoid hydrocarbons in trifluoroacetic acid containing lithium trifluoroacetate, are described. With electron-rich compounds, oxidation is rapid at room temperature; the products are biaryls, diarylmethanes, and trifluoroacetate esters, the proportions of which depend on the structure of the aromatic compound. Evidence is presented that the first step is the transfer of one electron to the oxidant to form an aromatic radical cation; with methyl-substituted benzenes, this is followed either by reaction with another aromatic molecule or by deprotonation, subsequent reactions then yielding an ester or a diarylmethane.