Synthesis of alpha-fluorocarboxylates from the corresponding acids using acetyl hypofluorite

alpha -Fluorocarboxylic esters and acids were synthesized in good yields. T he corresponding esters and acids were converted to their ketene acetals, a nd these enol derivatives reacted with AcOF made directly from fluorine. Th is route circumvents the problems associated with nucleophilic fluorination s such as various eliminations and rearrangements. alpha- and beta -branche d carboxylic acid derivatives that cannot be directly fluorinated gave by t his electrophilic fluorination the corresponding alpha -fluoro derivatives in good yield. Both the fluorination reaction and the preparation of AcOF a re fast and suitable for [18]F incorporation into acids and esters needed f or working with PET. alpha -Fluoroibuprofen (20) and methyl 2-fluoro-3,3,3- triphenylpropionate (32) are two examples of this general reaction.