Combinations of Ethers and B(C6F5)3 Function as Hydrogenation Catalysts

Hounjet, Lindsay J.; Bannwarth, Christoph; Garon, Christian N.; Caputo, Christopher B.; Grimme, Stefan; Stephan, Douglas W.

doi:10.1002/ange.201303166

Cited by 76 publications

(28 citation statements)

References 53 publications

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“…28,29 A notable example is hydrogen activation by B(C 6 F 5 ) 3 and diethyl ether. 30 Closely related to the FLP activation of H 2 is the activation of SiH bonds. 31 Although this was discovered by Piers and co-workers 3236 a number of years prior to the articulation of the concept of FLPs, it is clear that this Lewis acid-mediated hydrosilylation proceeds via an FLP mechanism.…”

Section: Overview Of Frustrated Lewis Pairsmentioning

confidence: 99%

“…Since the initial finding of H 2 activation by FLPs, this "ambiphilic" approach to small molecule activation has been 44 anilines, 22 phosphines, 8,27 carbenes, 45,46 ethers, 30 ketones, 20,21,47 thioethers, 48 and telluroethers 49,50 as well as more exotic bases such as carbodiphosphoranes, 51 silylenes, 52 and boron anions. 53 In contrast, the breadth of Lewis acids has been limited: the majority of FLP chemistry has utilized perfluorinated group 13 Lewis acids, most notably the commercially available Lewis acid B(C 6 F 5 ) 3 and related derivatives.…”

Section: Overview Of Frustrated Lewis Pairsmentioning

confidence: 99%

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Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Weicker

Stephan

2015

Bulletin of the Chemical Society of Japan

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112

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The advent of frustrated Lewis pair (FLP) chemistry almost a decade ago was based on the reactivity of sterically encumbered combinations of electrophilic boranes and phosphines with hydrogen. Since that time the chemistry has broadened dramatically in terms of reactivity and applications. Nonetheless, the majority of the work has continued to exploit the borane B(C6F5)3. In this review, we describe FLP chemistry that has developed by employing alternatives to this Lewis acid. Lewis acids derived from group 13, 14, and 15 based systems are described, thus demonstrating a growing area in the main group reactivity based on FLPs.

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Section: Overview Of Frustrated Lewis Pairsmentioning

confidence: 99%

Section: Overview Of Frustrated Lewis Pairsmentioning

confidence: 99%

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Weicker

Stephan

2015

Bulletin of the Chemical Society of Japan

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112

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“…According to this model of H 2 activation, a number of Lewis bases apart from phosphines should be viable molecules for heterolytic hydrogen splitting. Indeed, a vast number of Lewis bases for such purpose have been identified, ranging from bisphosphines [16], phosphinimines [17], imines [18], amines [19], and diethyl ether [20], through carbenes [21] to carbanions [22]. The most commonly used FLPs for H 2 activation consist of an amine or phosphine as the Lewis base and B(C 6 F 5 ) 3 as the Lewis acid.…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

“…Even diethyl ether can act as the Lewis base in combination with B(C 6 F 5 ) 3 as hydrogenation catalyst for olefins. The presence of 2 equiv of Et 2 O relative to B(C 6 F 5 ) 3 was found to facilitate the H 2 cleavage and was necessary to stabilize the diethyloxonium cation through hydrogen bonding (Figure 9.42) [20].…”

Section: Hydrogenation Of Unpolarized Olefins and Polycyclic Aromaticmentioning

confidence: 99%

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Cooperative H ₂ Activation by Borane‐Derived Frustrated Lewis Pairs

Paradies¹

2015

Cooperative Catalysis

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Frustrated Lewis Pair Catalyzed Hydroamination of Terminal Alkynes

Mahdi

Stephan

2013

Angewandte Chemie

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Much of the recent research in the area of frustrated Lewis pairs (FLPs) has focused on hydrogenation catalysis. [1] While initial reports described a limited substrate scope, recent advances have included the demonstration of metal-free hydrogenation of olefins, [2] anilines, [3] N-heterocyclic compounds, [4] and alkynes, [5] as well as enantioselective hydrogenation of imines. [6] Moreover, FLPs have also found applications in polymerization catalysis. [7] To date, the majority of the reported reactions of FLPs with small-molecule substrates is stoichiometric. For example, we have reported reactions of alkynes with FLPs comprised of B(C 6 F 5 ) 3 or Al(C 6 F 5 ) 3 ·(PhMe) with phosphines, resulting in either addition or deprotonation products. [8] The addition pathway affords zwitterionic vinyl phosphonium borate or alumininate salts. In contrast, the deprotonation pathway affords phosphonium alkynylborates or aluminates. The course of the reaction is dependent on the basicity of the phosphine. In related work, the groups of Berke [9] and Erker [10] have studied the reactivity of terminal and internal alkynes with the Lewis acid B(C 6 F 5 ) 3 , uncovering the fascinating 1,1-carboboration reactions, which afford alkenylboranes. Despite this reactivity, Erker and co-workers showed that B(C 6 F 5 ) 3 can mediate the intramolecular cyclization of an ortho-ethynylaniline to access a cyclic anilinium borate. [11] Berke and co-workers investigated related intermolecular reactions of alkynes and B(C 6 F 5 ) 3 with 2,6-lutidine and 2,2,5,5-tetramethylpiperidine, [9] demonstrating that these systems effect deprotonation of the terminal alkyne to afford ammonium alkynylborates.In order to expand the scope of applying FLPs in catalysis, we turned our attention to hydroaminations. A wide variety of catalysts based on rare-earth metals, [12] early- [13,14] and latetransition metals, [15] as well as lanthanides [16] and actinides [17] have been previously reported. Nonetheless, metal-free routes remain less explored. In a recent report, the exploitation of hydroxylamines to effect metal-free hydroamination of alkynes was illustrated, although forcing conditions were required. [18] In the present study, we show that B(C 6 F 5 ) 3 promotes the addition of aryl amines to alkynes, comprising a metal-free approach to catalytic hydroamination to afford the products of a Markovnikov addition. Moreover, subsequent to hydroamination catalysis, the borane catalyst can also be exploited for metal-free catalytic hydrogenation, providing a one-pot stepwise catalytic route to the corresponding amine derivatives.

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Combinations of Ethers and B(C₆F₅)₃ Function as Hydrogenation Catalysts

Cited by 76 publications

References 53 publications

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Cooperative H ₂ Activation by Borane‐Derived Frustrated Lewis Pairs

Frustrated Lewis Pair Catalyzed Hydroamination of Terminal Alkynes

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Combinations of Ethers and B(C6F5)3 Function as Hydrogenation Catalysts

Cited by 76 publications

References 53 publications

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Cooperative H 2 Activation by Borane‐Derived Frustrated Lewis Pairs

Frustrated Lewis Pair Catalyzed Hydroamination of Terminal Alkynes

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Product

Resources

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Combinations of Ethers and B(C₆F₅)₃ Function as Hydrogenation Catalysts

Cooperative H ₂ Activation by Borane‐Derived Frustrated Lewis Pairs