From cyclic (alkyl)(amino)carbene (CAAC) precursors to fluorinating reagentsGruden, Evelin (Avtor) Prinčič, Griša Grigorij (Avtor) Hočevar, Jan (Avtor) Iskra, Jernej (Avtor) Kvíčala, Jaroslav (Avtor) Tavčar, Gašper (Avtor) CAAC precursorfluorinating reagentpolyhydrogen fluoridesAddition of anhydrous HF to the hydrochloride [$^{Me}$CAACH][Cl(HCl)$_{0.5}$] resulted in the formation of salts with high HF content. By stepwise removal of HF in vacuo, we selectively prepared [$^{Me}$CAACH][F(HF)$_2$] (3) and [$^{Me}$CAACH][F(HF)$_3$] (4). We also characterised a salt with [F(HF)$_4$]$^−$ anions within the structure of [$^{Me}$CAACH][F(HF)$_{3.5}$] (5). Compounds with a lower content of HF were not accessible under vacuum conditions. $^{Me}$CAAC(H)F (1) was selectively prepared by abstraction of HF from 3 with CsF or KF, while [$^{Me}$CAACH][F(HF)] (2) was prepared by mixing 3 and 1 in a 1 : 1 ratio. Compound 2 proved to be quite unstable as it tends to disproportionate into 1 and 3. This observation triggered our computational study, in which the structural relationships between CAAC-based fluoropyrrolidines and dihydropyrrolium fluorides were investigated using different DFT methods. The study showed that the results were very sensitive to the computational method used. For a correct description, the quality of the triple-ζ basis set was crucial. Surprisingly, the isodesmic reaction of [$^{Me}$CAACH][F] + [$^{Me}$CAACH][F(HF)$_2$] → [$^{Me}$CAACH][F(HF)] + [$^{Me}$CAACH][F(HF)] did not confirm the low thermodynamic stability of 2. Furthermore, the use of 3 as a nucleophilic fluorinating reagent was tested on a range of organic substrates, as it is the most stable compound in this series. It was found to have the potential to fluorinate benzyl bromides, 1- and 2-alkyl bromides, silanes and sulfonyls with good to excellent yields of the target fluorides.20232023-11-22 14:09:02Članek v reviji152365sl