Regiospecific incorporation of no-carrier-added radiobromine and radioiodine into aromatic rings via halogenodegermylation

Abstract

A series of para-substituted aryltrimethylgermanium compounds have been used as model compounds with ⁷⁷Br and ¹³¹I to assess the utility of no-carrier-added (n.c.a.) halogenodegermylation as a regiospecific halogenation method. With dichloramine-T as an oxidant, high radiochemical yields were rapidly obtained in both activated and deactivated ring systems using n.c.a. ¹³¹I with a variety of solvents at 25 °C. Use of n.c.a. ⁷⁷Br resulted in high yields with activated systems in methanol at 25 °C, and with both activated and deactivated ring systems in the presence of acid or with warming. Halogenation was regiospecific in all cases. High yields, regiospecificity, rapid kinetics, and the low concentration of oxidant required make aromatic n.c.a. halogenodegermylation a useful method for labelling radiopharmaceuticals.