Radiosynthesis of 5-[18F]Fluoro-1,2,3-triazoles through Aqueous Iodine-[18F]Fluorine Exchange Reaction.

In this report, a simple and efficient process to achieve fluorine-18-labeled 1,2,3-triazole is reported. The heteroaromatic radiofluorination was successfully achieved through an iodine-fluorine-18 exchange in an aqueous medium requiring only trace amounts of base and no azeotropic drying of fluorine-18. This methodology was optimized on a model reaction and further validated on multiple 1,2,3-triazole substrates with 18-60% radiochemical conversions. Using this strategy-the radiosynthesis of a triazole-based thiamin analogue-a potential positron emission tomography (PET) probe for imaging thiamin-dependent enzymes was synthesized with 10-16% isolated radiochemical yield (RCY) in 40 min (uncorrected, n > 5).