Chemical reactivity of the 18F electrophilic reagents from the 18O(p,n) 18F gas target systems.

A comprehensive evaluation of the reactivity of 18F electrophilic fluorinating agents derived from the 18O(p,n)18F reaction conducted in target bodies made of aluminum, silver, copper, nickel, and gold-plated copper is reported. Two representative electrophilic reactions, namely addition across a double bond and substitution on an aromatic ring (fluorodemercuration and fluorodestannylation), were tested with the 18F activity generated in the [18O]O2 target systems. Identical reactions were also conducted with analogous nonradioactive fluorinating agents as control experiments. The products of all these reactions were analyzed by NMR spectroscopy. Results of these experiments clearly showed that 18F activities recovered from aluminum, silver, and copper target bodies were better suited for radiochemical syntheses, irrespective of the irradiation protocols employed. The 18F activity from a gold-plated target was suitable only for addition reactions. Further, the fluorodemercuration reaction essentially failed with the single-step irradiation technique conducted in nickel and gold-plated targets. In contrast, the fluorodestannylation reaction was quite successful with the 18F reagents recovered from all the target bodies and irradiation protocols.