Brian P. Swann

Thallium in organic synthesis—XVI: Preparation of p-quinones by oxidation of phenols and hydroquinones with thallium(III) trifluoroacetate

Abstract Treatment of 2,6-disubstituted-4-t-butylphenols with thallium(III) trifluoroacetate in either trifluoroacetic acid or carbon tetrachloride as solvent results in loss of the 4-t-butyl substituent as isobutene and formation in high yield of the corresponding 2,6-disubstituted p-quinones. Possible mechanisms for this novel reaction, which probably proceeds via the intermediacy of a hydroquinone or hydroquinone mono-trifluoroacetate ester, are discussed. Consequent to these mechanistic considerations, thallium(III) trifluoroacetate is shown to be a highly efficient oxidant for the conversion ofhydroquinones and a variety of 2,4,6-trisubstituted phenols into the corresponding p-quinones.