Direct n.c.a. electrophilic radioiodination of deactivated arenes with N-chlorosuccinimide

Article abstract of DOI:10.1002/1099-1344(200006)43:7<721::AID-JLCR357>3.0.CO;2-K

An efficient method for the direct electrophilic no-carrier-added (n.c.a.) radioiodination of deactivated arenes has been developed using N-chlorosuccinimide (NCS)/radioiodide in trifluoromethanesulfonic acid (triflic acid). Optimization of the one pot labelling procedure using chlorobenzene as a model substrate resulted in a radiochemical yield of 75% within 15 min at room temperature. Drying of the aqueous radioiodide solution prior to radiolabelling was not required. Radioiodination of weakly activated and deactivated monosubstituted benzene derivatives gave rise to radiochemical yields of about 80% with an electrophilic substitution pattern. Strongly deactivated aromatic compounds were radioiodinated with high radiochemical yields of about 70% exclusively in their meta-position using a reaction temperature of 75°C and a reaction time of 1 h. With regard to the reaction mechanism, in situ formed radioiodo(I) trifluoromethanesulfonate (triflyl [¹³¹I]hypoiodite) is discussed as electrophilic reagent.