[18F] Fluoromethyl iodide ([18F] FCH2I) preparation and reactions with phenol, thiophenol, amide and amine functional groups

In this study, we report the synthesis and reactivity of [F-18]fluoromethyl iodide ([F-18]FCH2I) with various nucleophilic substrates and the stabilities of [F-18]fluoromethylated compounds. [F-18]FCH2I was prepared by reacting diiodomethane (CH2I2) with [F-18]KF, and purified by distillation in radiochemical yields of 14-31% (n = 25). [F-18]FCH2I was stable in organic solvents commonly used for labeling and aqueous solution with pH 1-7, but was unstable in basic solutions. [F-18]FCH2I displayed a high reactivity with various nucleophilic substrates such as phenol, thiophenol, amide and amine. The [F-18]fluoromethylated compounds synthesized by the reactions of phenol. thiophenol and tertiary amine with [F-18]FCH2I were stable for purification, formulation and storage. In contrast, the [F-18]fluoromethylated compounds synthesized by the reactions of primary or secondary amines, and amide with [F-18]FCH2I were too unstable to be detected or purified from the reaction mixtures. Defluorination of these [F-18]fluoromethyl compounds was a main decomposition route. (C) 2004 Elsevier B.V. All rights reserved.