anisole requires a full equivalent of FeBr3, and furnished the product (4z"a) in 20% yield. tert-Alkylation of 4-ethylanisole led to product 4pd in 90% yield, but 4-tert-butylanisole turned out to be a more challenging substrate, likely owing to the added steric bulk, forming alkylation product 4vd in 52% yield. The reaction accommodates esters, providing product 4wd in 50% yield. In contrast to previously studied halogenated arenes, 4bromoanisole was converted to product 4z"'d in quantitative yield. This tert-alkylation reaction is not confined to phenolic and aryl ether substrates. ortho-Xylene and tetralin are alkylated to provide arenes 5aa, 5ac, 5ad, and 5ba in 35-97% yields. In contrast to the TFA/FeCl3 system where the kinetics are well-behaved (see Scheme 3 & Figure ), the occurrence of induction periods that complicate the kinetics analysis are observed with the HCl/FeCl3 pair. The reaction rates during the acceleration periods following the induction periods are invariably constant and does not appear to be affected by concentrations of FeCl3, HCl, phenolic substrate, nor t-butanol, thereby resembling zero-order behaviors in all cases (see SI).