No-carrier-added radiobromination and radioiodination of aromatic rings using in situ generated peracetic acid

Abstract

Peracetic acid generated in situ from aqueous hydrogen peroxide and glacial acetic acid was examined as an oxidizing agent for electrophilic aromatic bromination and iodination without chlorinated side products. No-carrier-added (n.c.a.)⁷⁷Br and ¹³¹I were used with simple organic aromatic compounds or aryltrimethyl-tin, -germanium, and -silicon organometailic compounds to identify reaction parameters which influence this electrophilic halogenation method. N.c.a. aromatic halogenodeprotonation using peracetic acid was relatively slow and resulted in high labelling yields only with aromatic rings that were activated toward electrophilic substitution. By contrast, high radiochemical yields were rapidly obtained via iododestannylation of aromatic rings regardless of their degree of electronic activation. Useful labelling yields were also achieved using bromodestannylation reactions with aromatic rings deactivated toward electrophiles, but optimum yields with activated systems required the use of germylated arenes as substrates. The practical aspects of aromatic halogenodemetallation and halogenodeprotonation as n.c.a. electrophilic halogenation techniques with in situ generated peracetic acid are outlined.