Facile aromatic radiofluorination of [18F]flumazenil from diaryliodonium salts with evaluation of their stability and selectivity†
Abstract
Aromatic radiofluorination of the diaryliodonium tosylate precursor with [18F]fluoride ions has been applied successfully to access [18F]flumazenil in high radiochemical yields of 67.2 ± 2.7% (decay corrected). The stability and reactivity of the diaryliodonium tosylate precursor plays a key role in increasing the production of 18F-labelled molecules under the fluorine-18 labelling condition. Various conditions were explored for the preparation of [18F]flumazenil from different diaryliodonium tosylate precursors. Optimum incorporation of [18F]fluoride ions in the 4-methylphenyl-mazenil iodonium tosylate precursor (5f) was achieved at 150 °C for 5 min by utilizing 4 mg of the precursor, K2.2.2/K2CO3 complex, and the