The dual processes of electrophilic aromatic thallation, followed by replace- ment of the resulting thallium substituent by anions, olefins, arenes, or cations, represents a versatile methodology for controlled aromatic substitution [ 21. A notable limitation to date, however, is the susceptibility of electron-rich arenes to oxidative dimerization under normal thallation conditions; ie, thallium tris(trifluoroacetate) (TTFA) in trifluoroacetic acid (TFA) [3,4]. We describe in this paper a ...
