Preparation of Organotrifluoroborate Salts: Precipitation-Driven Equilibrium under Non-Etching Conditions


  • We thank AstraZeneca PR&D (Dr. M. Kenworthy, Dr. P. M. Murray, Dr. M. Butters) for funding and Thomas Hornsby and Thomas Carter (Bristol Synthesis DTC) for preliminary studies. G.C.L.-J. is a Royal Society Wolfson Research Merit Award Holder.


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Simple, rapid, and scaleable: In contrast to current procedures using corrosive HF/MF or MHF2 reagents (M=e.g. K), a wide range of trifluoroborates can be rapidly, simply, and safely prepared from MF (M=K, Cs), RCO2H, and a boronic acid/ester in regular glassware (see figure; left versus right). The use of L-(+)-tartaric acid as an alkali-metal sponge is key and allows isolation of RBF3M by a simple stir/filter/evaporate sequence.