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

Abstract

The hydrofluorocarbon 245 isomers, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2- pentafluoropropane, and 1,1,1,2,3-pentafluoropropane (HFC-245fa, HFC-245cb, and HFC-245eb) were activated through C–F bond activations using aluminium chlorofluoride (ACF) as a catalyst. The addition of the hydrogen source Et3SiH is necessary for the activation of the secondary and tertiary C–F bonds. Multiple C–F bond activations such as hydrodefluorinations and dehydrofluorinations were observed, followed by hydroarylation and Friedel–Crafts-type reactions under mild conditions.

Nickel-Catalyzed Exhaustive Hydrodefluorination of Perfluoroalkyl Arenes

“…26 Some reactions of fluoroalkanes promoted by addition of strong Lewis acids afforded alkenes by formal elimination of HF. 29,30 Our mechanistic study suggested that this step is promoted by Ni/ICy, although the reason for this remains unclear at this stage. Subsequently, the difluoroalkene is rapidly transformed into the vinyl arene via the cleavage of the C(sp 2 )−F bonds.…”

Chlorodefluorination of Fluoromethanes and Fluoroolefins at a Lewis Acidic Aluminum Fluoride

“…Any intermediate carbenium‐like species will be allylic, which leads to further stabilization [7d,29,31] . This can also include allylic substitution for compound 16 via an initial fluoride abstraction [7d,g,29] . However, the unusual C(sp 2 )−F bond activation steps presumably proceed via a different mechanism based on an ACF mediated addition of chlorosilane at the double bond followed by fluorosilane elimination reaction (Scheme 8).…”

“…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] .…”

“…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] . More recently, the dehydrofluorination of polyfluoropropanes led to the synthesis of industrially relevant fluoroolefins [7g] . In addition, the activation of 1‐fluoropentane at ACF resulted in dehydrofluorination in the presence of HGeEt 3 , but when HSiEt 3 was used instead, Friedel‐Craft products were obtained [7e] .…”

Competing C–H and C–F bond activation reactions of a fluorinated olefin at Rh: a fluorido vinylidene complex as an intermediate in an unprecedented dehydrofluorination step

“…29 Hydrodeuorination is a very well-known reaction pathway at transition metal complexes for both stoichiometric and catalytic activation of uorinated derivatives. 15,18,[30][31][32][33][34] On the contrary, dehydrouorination (DHF) reactions at uoroalkanes are rare, but can be catalysed by solid materials such as magnesium- 35 or aluminium-based catalysts, 36,37 and germylium ions as the only examples for homogeneous catalysts. 38 Metalmediated dehydrouorination reactions of uoroalkyl or uoroalkenyl moieties to yield HF and the corresponding alkenyl or alkynyl entity have not been described previously.…”