• In the presence of an Ag(II) species (from silver nitrate and ammonium persulfate in TFA), tert-butyl radicals are generated. With quinoline, the 2-tert-butyl substituted derivative is formed in high yield: Tetrahedron, 46, 2525 (1990), whereas for most other carboxylic acids, both 2- and 4-substitution usually occur.