Deoxyfluorination with superacids - synthesis and characterization of protonated α-fluorohydroxyacetic acid.

α-Fluoroalcohols describe a rare and unstable class of compounds, accessible mainly by fluorination of highly electrophilic carbonyl compounds. In this work, we report the syntheses of α-fluorohydroxyacetic acid (FHA) and its acyl fluoride (FHA-F) by reacting the dihydroxy species glyoxylic acid monohydrate (GAM) with SF. Surprisingly, only one of the geminal hydroxy groups is substituted when excess SF is employed. Implementing GAM with the binary superacid HF/AsF also leads to a single yet quantitative deoxyfluorination at the diol group. The reaction pathways are discussed based on NMR experiments, the characterization was carried out using NMR and vibrational spectroscopy as well as single-crystal X-ray diffraction.