Koser's reagents are very useful iodine(III) reagents due to their ease of preparation as well as favorable stability and established reactivity. Indeed, Kita and coworkers reported the efficient synthesis of diaryliodonium tosylates from Koser's reagent and arenes, demonstrating that trifluoroethanol (TFE) significantly improved the reactivity and scope. Our group has developed a room-temperature synthesis of 7 using equimolar amounts of m-CPBA and TsOH•H2O in CH2Cl2/TFE 1:1. However, that method cannot accommodate iodoarenes bearing multiple strong electronwithdrawing substituents due to insufficient oxidation in the presence of tosic acid. Gratifyingly, the corresponding products 7 could be obtained in high yields from 1 by using a slight excess of m-CPBA and TsOH in CH2Cl2 at 60 °C for 2 h (Scheme 3a). Reaction of 7 with arenes 2 through ligand exchange by EAS proceeded well at rt in various fluorinated solvents that were chosen to match the nucleophilicity of 2, giving 3i-3m in good to excellent yields (Scheme 3b). Previous attempts to make product 3j through route A were unsuccessful, yielding complex reaction mixtures. In contrast, route C allows for efficient and clean product formation. Furthermore, product 3k with an electron rich pyridyl ligand is preferentially prepared by this method to avoid oxidation and undesired nitrogen protonation of the corresponding heteroarene 2.