Pinacolatoboron fluoride (pinBF) is an efficient fluoride transfer agent for diastereoselective synthesis of benzylic fluorides
Cresswell AJ., Davies SG., Figuccia ALA., Fletcher AM., Heijnen D., Lee JA., Morris MJ., Kennett AMR., Roberts PM., Thomson JE.
The incorporation of alkoxy ligands within a range of alkoxyfluoroboranes and dialkoxyfluoroboranes results in fluoroborane reagents with attenuated Lewis acidity and increased ability to donate fluoride ion(s) when compared to boron trifluoride itself. Pinacolatoboron fluoride (pinBF), prepared in situ from BF3·OEt2 and bis(O-trimethylsilyl)pinacol, has been identified as an efficient fluoride donor which allows highly stereoselective SN1-type epoxide ring-opening (with retention of configuration) of a range of trans-β-methyl-substituted aryl epoxides to give the corresponding syn-fluorohydrins. The substrate scope of this transformation is more broad than the analogous protocol using boron trifluoride alone.