A HF Loaded Lewis‐Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

Abstract

The very strong Lewis acid aluminium chlorofluoride (ACF) was loaded with anhydrous HF. The interaction between the surface of the catalyst and HF was investigated using a variety of characterization methods, which revealed the formation of polyfluorides. Moreover, the reactivity of the HF‐loaded ACF towards the hydrofluorination of alkynes was studied.

Chlorodefluorination of Fluoromethanes and Fluoroolefins at a Lewis Acidic Aluminum Fluoride

“…Thus, the reaction of 1,1,3,3,3‐pentafluoropropene ( 5 ) with ClSiEt 3 catalyzed by ACF at 70 °C in C 6 D 6 gave a mixture of trans ‐1‐chloro‐1,3,3,3‐tetrafluoro‐1‐propene ( 6 a ) (27 %), [24] cis ‐1‐chloro‐1,3,3,3‐tetrafluoro‐1‐propene ( 6 b ) [24] (16 %) as well as monodeuterated 1,1,1,3,3,3‐hexafluoropropane ( 7 d ) [25] (13 %) and 1,1‐dichloro‐3,3,3‐trifluoro‐1‐propene ( 8 ) [24] (4 %) (Scheme 4). While compounds 6 and 8 stem from the halogen exchange reaction, compound 7 d seems to be formed by hydrofluorination of 5 with HF followed by H/D exchange [20a,26] …”

An Amorphous Teflate Doped Aluminium Chlorofluoride: A Solid Lewis‐Superacid for the Dehydrofluorination of Fluoroalkanes

“…It has been synthesized by fluorination of AlCl 3 with CCl 3 F and applied in a variety of conversions such as C−H activation, fluorination, defluorination or Friedel‐Crafts type conversions [3] . Especially hydrodefluorination type reactions can be promoted by the presence of silanes and silylium‐type surface species might play a crucial role to induce the C−F bond cleavage reactions [3c,4] . A variety of other Lewis‐acidic amorphous aluminium fluoride catalyst were developed such as the mesoscopic high‐surface ‐AlF 3 [5] .…”

An amorphous Lewis-acidic zirconium chlorofluoride as HF shuttle: C–F bond activation and formation

“…Regioselectivities follow the Markovnikov rule and are consistent with hydrofluorination reactions of alkynes to give difluoroalkanes at HF-loaded ACF, and with approaches that apply the HF source PVP-HF (PVP: poly[4-vinylpyridinium poly(hydrogen fluoride)]) or a combination of KHSO 4 -13HF and DMPU-12HF. 13,38,39 At ZCF electron-rich alkynes showed a higher reactivity compared to electron-poor species, even after prolonged reaction times. Note also that, in contrast, homogeneously catalysed reactions using Au( i ) and Pt( ii ) species as catalysts typically yield monofluoroalkenes.…”

“…The generation of the difluoroalkane shows that an independent alkyne fluorination at ZCF is indeed possible. 13…”