A mild and efficient rhenium-catalyzed transfer hydrogenation of terminal olefins using alcoholysis of amine–borane adducts as a reducing system

Dong, Hailin; Berke, Heinz

doi:10.1016/j.jorganchem.2011.01.027

“…12 Moreover, 13 gives a slightly higher extent of H 2 release, 2.1 equiv. Ethanol here is a cocatalyst: although it has known reactivity with AB, particularly when present as solvent and activated by base, 19 we have shown Scheme 1. Proposed AB Dehydrogenation Mechanism by Shvo's Catalyst Figure 2.…”

Section: ■ Introductionmentioning

confidence: 82%

Nitrogen-Based Ligands Accelerate Ammonia Borane Dehydrogenation with the Shvo Catalyst

Zhang

¹

,

Lü

²

,

Foellmer

³

et al. 2015

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We previously reported that quantitative poisoning, a test for homogeneous catalysis, behaves oddly in the dehydrogenation of ammonia borane (AB) by Shvo's catalyst, whereas the "poison" 1,10-phenanthroline (phen) accelerates catalysis and apparently prevents catalyst deactivation. Thus, we proposed a protective role for phen in the catalysis. Herein we account for the mechanistic origin of this accelerated AB dehydrogenation in the presence of phen and define the relevance boundaries of our prior proposal. In so doing, we present syntheses for novel amine-and pyridineligated homologues of the Shvo catalyst and show their catalytic efficacy in AB dehydrogenation. These catalysts are synthetically easy to access, air stable, and rapidly release over 2 equiv of H 2 . The mechanisms of these reactions are also discussed.

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“…BH 3 could immediately form an adduct with the C=O moiety of the substrate and hydroboration would form the borate ester intermediate which then undergoes methanolysis to give the products. Alternatively, a MeOH⋅BH 3 adduct could form after dissociation and undergo direct hydrogenation via a double H transfer with the protic hydrogen coming from the alcohol [28] . Deuterium labeling experiments were unable to distinguish between these two pathways.…”

Section: Solvolysis Of Amine–boranes In Nonclassical Th Reactionsmentioning

confidence: 99%

“…The authors followed up on the TH with Me 2 HN•BH 3 by using the five-coordinate [Re(Br)(NO)(PCy 3 )(H)(L)] (L = 1,3-dimesitylimidazol-2-ylidene IMes or PCy 3 ) precatalyst, which allowed a slight increase in the reaction efficiency (Scheme 13 b). [27b] Subsequently the Re-catalyzed TH reaction was applied to the reduction of terminal olefins, [28] relying, however, on the ethanolysis of amine-boranes (Section 4).…”

Section: Metal Catalysismentioning

confidence: 99%

Amine–Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective

Lau

¹

,

Gasperini

²

,

Webster

³

2021

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Transfer hydrogenation (TH) has historically been dominated by Meerwein–Ponndorf–Verley (MPV) reactions. However, with growing interest in amine–boranes, not least ammonia–borane (H3N⋅BH3), as potential hydrogen storage materials, these compounds have also started to emerge as an alternative reagent in TH reactions. In this Review we discuss TH chemistry using H3N⋅BH3 and their analogues (amine–boranes and metal amidoboranes) as sacrificial hydrogen donors. Three distinct pathways were considered: 1) classical TH, 2) nonclassical TH, and 3) hydrogenation. Simple experimental mechanistic probes can be employed to distinguish which pathway is operating and computational analysis can corroborate or discount mechanisms. We find that the pathway in operation can be perturbed by changing the temperature, solvent, amine–borane, or even the substrate used in the system, and subsequently assignment of the mechanism can become nontrivial.

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“…The authors followed up on the TH with Me 2 HN⋅BH 3 by using the five‐coordinate [Re(Br)(NO)(PCy 3 )(H)(L)] (L=1,3‐dimesitylimidazol‐2‐ylidene IMes or PCy 3 ) precatalyst, which allowed a slight increase in the reaction efficiency (Scheme 13 b). [27b] Subsequently the Re‐catalyzed TH reaction was applied to the reduction of terminal olefins, [28] relying, however, on the ethanolysis of amine–boranes (Section 4).…”

Section: Catalyzed Classical Th Reactionsmentioning

confidence: 99%

Amine–Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective

Lau

¹

,

Gasperini

²

,

Webster

³

2021

View full text Add to dashboard Cite

Transfer hydrogenation (TH) has historically been dominated by Meerwein–Ponndorf–Verley (MPV) reactions. However, with growing interest in amine–boranes, not least ammonia–borane (H3N⋅BH3), as potential hydrogen storage materials, these compounds have also started to emerge as an alternative reagent in TH reactions. In this Review we discuss TH chemistry using H3N⋅BH3 and their analogues (amine–boranes and metal amidoboranes) as sacrificial hydrogen donors. Three distinct pathways were considered: 1) classical TH, 2) nonclassical TH, and 3) hydrogenation. Simple experimental mechanistic probes can be employed to distinguish which pathway is operating and computational analysis can corroborate or discount mechanisms. We find that the pathway in operation can be perturbed by changing the temperature, solvent, amine–borane, or even the substrate used in the system, and subsequently assignment of the mechanism can become nontrivial.

show abstract

A mild and efficient rhenium-catalyzed transfer hydrogenation of terminal olefins using alcoholysis of amine–borane adducts as a reducing system

Cited by 24 publications

References 48 publications

Nitrogen-Based Ligands Accelerate Ammonia Borane Dehydrogenation with the Shvo Catalyst

Nitrogen-Based Ligands Accelerate Ammonia Borane Dehydrogenation with the Shvo Catalyst

Amine–Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective

Amine–Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective

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