Chlorodefluorination of Fluoromethanes and Fluoroolefins at a Lewis Acidic Aluminum Fluoride

Abstract

Chlorodefluorination reactions of fluoromethanes and fluoroolefins catalysed by the highly Lewis acidic nanoscopic aluminum chlorofluoride (ACF, AlClxF3−x, x≈0.05–0.3) in the presence of ClSiEt3 were studied. Both fluoromethanes and fluoroolefins convert under mild reaction conditions by fluorine‐chlorine exchange steps into chlorinated fluoro derivatives. MAS NMR studies provided information on the interaction of silanes and hexafluoropropene with the ACF surface.

Insights into the Mechanism of Aluminum-Catalyzed Halodefluorination

“…This barrier mainly amounts to the energetic cost required for the activation of TMSCl. Although this pathway (involving activated TMSCl) was deemed kinetically inaccessible compared to the much lower reaction barrier of TS I , a similar mechanism was proposed by Braun for halodefluorination reactions involving TMSCl and heterogeneous aluminum chlorofluoride catalyst …”

“…Although this pathway (involving activated TMSCl) was deemed kinetically inaccessible compared to the much lower reaction barrier of TS I , a similar mechanism was proposed by Braun for halodefluorination reactions involving TMSCl and heterogeneous aluminum chlorofluoride catalyst. 8 Given the much lower barrier for C−F activation via an AlCl 3 -mediated S N 1 mechanism, we then investigated the possibilities for halide delivery to the intermediate carbocation (Figure 3). We have reported on selective C−F activation, where a Lewis base reacts directly with an intermediate carbocation.…”

Conversion of fluoroform to CHCl3 and AlClxF3−xvia its mechanochemical reaction with AlCl3

“…hydroarylation, hydrodefluorination, hydrodechlorination, dismutation, dehydrofluorination, and H/D exchange. 21 And it can even catalyze some reactions that SbF 5 fails to, such as the addition reaction of perfluoroalkenes higher than C3. 22 The used ACFs are all prepared via a strong exothermic reaction between AlCl 3 and CCl 3 F under rigorously controlled conditions.…”