Consecutive Transformations of Tetrafluoropropenes: Hydrogermylation and Catalytic C−F Activation Steps at a Lewis Acidic Aluminum Fluoride

Meißner, Gisa; Kretschmar, Konrad; Braun, Thomas; Kemnitz, Erhard

doi:10.1002/anie.201707759

Cited by 83 publications

(69 citation statements)

References 98 publications

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“…[18,19] In related studies,B raun and coworkers have documented the hydroboration, hydrosilylation, and hydrogermylation of aseries of fluoroalkenes (including HFOs) by Lewis acidic heterogeneous catalysts or homogeneous rhodium catalysts.T hese hydrofunctionalisation reactions often lead to complex mixtures of products because of competing addition and elimination pathways. [20][21][22] We,a nd others,h ave previously shown that the monomeric Al I reagent 1 reacts with C À Fb onds of fluoroalkanes and fluoroarenes; [23,24] herein, we describe the reaction of 1 with industrially relevant fluoroalkenes.This reactivity is an example of agrowing number of approaches in which alowvalent main-group metal mimics the redox behaviour of at ransition metal. [24][25][26][27][28][29][30] As part of this analysis we have isolated an unprecedented aluminium metallocyclopropane complex and show that the reaction of an alkene with 1 is reversible.…”

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confidence: 90%

Reactions of Fluoroalkenes with an Aluminium(I) Complex

2018

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A series of industrially relevant fluoroalkenes react with a monomeric Al complex. These reactions break strong sp and sp C-F bonds, and result in the formation of a diverse array of organoaluminium compounds. Mechanistic studies show that two mechanisms are likely in operation: 1) direct oxidative addition of the C-F bond to Al occurs with retention of alkene stereochemistry, and 2) stepwise formation and decomposition of a metallocyclopropane intermediate occurs with inversion of alkene stereochemistry. As part of this mechanistic analysis, we have isolated the first aluminium metallocyclopropane complex from oxidative addition of an alkene to Al . Remarkably this reaction is reversible and reductive elimination of the alkene occurs at higher temperature reforming Al . Furthermore, in selected cases the organoaluminium products are susceptible toward β-fluoride elimination to yield a double C-F activation pathway.

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confidence: 90%

Reactions of Fluoroalkenes with an Aluminium(I) Complex

2018

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“…[12] Recently, hydrosilylation of the same HFOs with triethylsilane under activation by aluminum chlorofluoride has been studied. [13] In the first case, the Haszeldine group worked with mixtures of olefins 1 and 2 to obtain complex mixtures, containing the desired silanes along with defluorination products. In the case of ACF-catalyzed activation, both olefins gave mixtures, containing products of hydrodefluorination without the desired silanes formation.…”

Section: Resultsmentioning

confidence: 99%

“…The best result was observed when the reaction was carried out at 120°C for 48 hours with 1.5-fold excess of starting silane and 200 ppm of catalyst ( Table 1, entry 7). The target silane 5a was isolated in 63 % yield and fully characterized with 1 H, 19 F, 13 C and 29 Si NMR spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Catalytic Hydrosilylation of Hydrofluoroolefins (HFOs): Synthesis of New Fluorinated Silanes and Diversity of their Synthetic Character

et al. 2020

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New polyfluorinated silanes were synthesized via the Pt, Rh and Pd catalyzed hydrosilylation of commercially available hydrofluoroolefins (HFOs) in moderate to excellent yields. HFO‐1234yf (2,3,3,3‐tetrafluoropropene‐1) and –1234ze (1,3,3,3‐tetrafluoropropene‐1) were reactive with Pt catalyst to form tetrafluoropropylsilanes along with defluorosilylation products. The Z‐ and E‐isomers of HFO‐1336mzz (1,1,1,4,4,4‐hexafluorobut‐2‐ene) gave the desired silanes with Pd catalysis in good to excellent yields, while with Pt catalyst only the dehydrofluorination product CF2=CHCH2CF3 (HFO‐1345czf, 1,1,4,4,4‐pentafluorobut‐1‐ene) was obtained. Synthetic applications of the new polyfluorinated silanes were illustrated by conversion of dichloro(hexafluorobutyl)(methyl)silane to the cyclic trisiloxane, which can serve as a monomer for the preparation of polysiloxanes. In addition, the hexafluorobutylsilanes showed defluorinative reactivity with lithium reagents, thereby demonstrating their synthetic utility as valuable building blocks for further transformations via C–F and C‐Si bond activation.

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“…In related studies, Braun and coworkers have documented the hydroboration, hydrosilylation, and hydrogermylation of a series of fluoroalkenes (including HFOs) by Lewis acidic heterogeneous catalysts or homogeneous rhodium catalysts. These hydrofunctionalisation reactions often lead to complex mixtures of products because of competing addition and elimination pathways …”

Section: Figurementioning

confidence: 99%

Reactions of Fluoroalkenes with an Aluminium(I) Complex

2018

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As eries of industrially relevant fluoroalkenes react with am onomeric Al I complex. These reactions break strong sp 2 and sp 3 C À Fbonds,and result in the formation of adiverse arrayo fo rganoaluminium compounds.M echanistic studies show that two mechanisms are likely in operation:1 )direct oxidative addition of the CÀFbond to Al I occurs with retention of alkene stereochemistry,a nd 2) stepwise formation and decomposition of am etallocyclopropane intermediate occurs with inversion of alkene stereochemistry.A sp art of this mechanistic analysis,w eh ave isolated the first aluminium metallocyclopropane complex from oxidative addition of an alkene to Al I .R emarkably this reaction is reversible and reductive elimination of the alkene occurs at higher temperature reforming Al I .Furthermore,inselected cases the organoaluminium products are susceptible toward b-fluoride elimination to yield adouble C À Factivation pathway.Scheme 1. Reaction of 1 with the stereoisomers of HFO-1234ze.

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Consecutive Transformations of Tetrafluoropropenes: Hydrogermylation and Catalytic C−F Activation Steps at a Lewis Acidic Aluminum Fluoride

Cited by 83 publications

References 98 publications

Reactions of Fluoroalkenes with an Aluminium(I) Complex

Reactions of Fluoroalkenes with an Aluminium(I) Complex

Catalytic Hydrosilylation of Hydrofluoroolefins (HFOs): Synthesis of New Fluorinated Silanes and Diversity of their Synthetic Character

Reactions of Fluoroalkenes with an Aluminium(I) Complex

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