Selective dehydrofluorination of 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) to 2-chloro-3,3,3-trifluoropropene (HFO-1233xf) using nanoscopic aluminium fluoride catalysts at mild conditions

Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

“…In the past two decades, metal fluoride catalysts, especially high-surface aluminium fluoride, HS-AlF 3 and amorphous ACF (aluminiumchlorofluoride, AlCl x F 3−x , x = 0.05−0.3), have shown high activity in several reactions such as C-H and C-F bond activation or hydroarylation reactions [1][2][3][4][5][6]. In selected reactions, these catalysts show comparable activity with the homogeneous catalyst SbF 5 [2].…”

Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination

“…The ratio between the olefin 1 and the refluorination product 10b observed in the presence of HSiEt 3 was 3:1, whereas, without the silane, a ratio of 1:2 was detected. This difference in the ratio might relate to the amount of HF present in the reaction mixture, which would be lower in the presence of silane because the latter can convert with HF into fluorosilane and H 2 [ 39 , 50 , 53 ]. Consequently, less refluorination takes place, and a higher selectivity towards the formation of the olefin 1 is observed.…”

“…Therefore, as an alternative to the initial formation of the surface silylium ion species at ACF, it is in principle also conceivable that carbenium species can be initially produced by an abstraction of a fluoride ion from a fluorinated group by the surface of the catalyst. Then, carbenium ions can react with silane to yield hydrodefluorination products, or after dehydrofluorination, HF that in the presence of silane, produces FSiEt 3 and H 2 [ 39 , 50 ]. Furthermore, any intermediate carbenium species, generated directly at the ACF surface or via interaction with a silylium species, can be engaged in Friedel–Crafts-like reactions to give with C 6 D 6 11 or 3 , which is consistent with previous studies [ 16 ].…”

“…In comparison, when ACF was loaded with germane, dehydrofluorination products were detected. Besides, 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) was as well effectively activated at ACF to yield the corresponding dehydrofluorination product 2-chloro-3,3,3-trifluoropropene (HFO-1233xf) without the use of any additional hydrogen source [ 50 ]. In the presence of silane and ACF, HFO-1233xf was further activated via allylic hydrodefluorination.…”

Chlorodefluorination of Fluoromethanes and Fluoroolefins at a Lewis Acidic Aluminum Fluoride

“…For the latter, aluminum chlorofluoride, (ACF, AlCl x F 3− x , x ≈0.05–0.3), which is an amorphous, nanoscopic solid Lewis acid, proofed to be suitable in heterogeneous catalytic C−F bond activation reactions [7] . Even though ACF itself shows strong catalytic ability, [7a–c,8] its catalytic performance becomes unique in the presence of main group compounds [7d–g,9] . Thus, ACF catalyzed the C−F bond activation of fluorinated methanes in the presence of HSiEt 3 , towards both Friedel‐Crafts and hydrodefluorination products depending on the solvent used [7f] .…”