Improved synthesis of pure [¹⁸F]fluoro-compounds for PET studies from bromo-compounds

For preparing [¹⁸F]labeled compounds free from bromo-compounds for PET (positron emission tomography) studies, we propose the following two processes in which no separation is needed between the fluoro-compound and bromo-compound: (1) the bromo-compound is first converted into O-tosylate, which is then [¹⁸F]fluorinated; and (2) after [¹⁸F] fluorination of the bromo-compound, its excess is converted into an easily separable compound, e.g., phthalimide-compound. Direct tosylation with silver tosylate was effected in 65-85% yield for most commercial bromo-compounds, and with potassium phthalimide, the bromo-compounds in cold run were converted easily into phthalimide-compounds in 84-90% yield.