Synthesis of TBAF; Anhydrous tetrabutylammonium fluoride (TBAF):; 0.67 g of tetrabutylammonium cyanide (TBACN) was dissolved in 2.5 ml of tetrahydrofuran (THF) and the resulting solution was cooled to -65 °C. In a separate vessel, 0.3 mL of hexafluorobenzene (C6F6) was dissolved in 0.5 mL of THF and cooled to -65°C. The hexafluorobenzene solution was slowly added to the cooled TBACN solution and the mixture was gradually warmed (over 4 hours) to -15°C. During the reaction, the solution changed from colorless to yellow-green and precipitated a white solid. The mixture was cooled again to -65 °C, the solid was collected by filtration and washed twice with cold THF. All separation operations need to be carried out below -36°C. The resulting white or light yellow TBAF solid can be stored in a refrigerator at -36°C for a short period of time. If the reaction mixture is used directly, the overall yield of TBAF exceeds 95% (based on TBACN, as verified by burst experiments with benzyl chloride). Isolated yields of the solid product ranged from 40% to 70%, depending on the efficiency of the washing and filtration steps.1H NMR ((CD3)2SO) δ 3.23 (8H, m), 1.56 (8H, m), 1.28 (8H, sextuple peak, J = 7.31 Hz), 0.86 (12H, t, J = 7.31 Hz); 19F NMR ((CD3)2SO) δ -72.6 ppm(s); 13C NMR ((CD3)2SO) δ 57.5, 23.1, 19.2, 13.5 ppm.
