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.