Metal‐Free Hydrogenation of Electron‐Poor Allenes and Alkenes

Inés, Blanca; Palomas, David; Holle, Sigrid; Steinberg, Sebastian; Nicasio, Juan A.; Alcarazo, Manuel

doi:10.1002/anie.201205348

Cited by 97 publications

(64 citation statements)

References 50 publications

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“…Good conversions were obtained using 2,6-lutidine as the amine base (Scheme 22). In a similar fashion, Alcarazo and coworkers [57] showed that the combination of B(C 6 F 5 ) 3 and DABCO or 2,6-lutidine (10-15 mol %) effectively hydrogenated allenic esters, such as 56 to the corresponding esters 57, respectively (Scheme 22). In a related sense, several enones were completely reduced in a domino hydrogenation/ hydrosilylation catalyzed by [2,2]-paracyclophane bisphosphine/B(C 6 F 5 ) 3 FLP catalysts (Scheme 23).…”

Section: Electron-poor Alkenes and Alkynesmentioning

confidence: 89%

Frustrated Lewis Pair Chemistry: Development and Perspectives

2015

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Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in solution that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-molecule binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently observed feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.

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Section: Electron-poor Alkenes and Alkynesmentioning

confidence: 89%

Frustrated Lewis Pair Chemistry: Development and Perspectives

2015

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“…Building on these initial findings, Paradies [34][35][36] demonstrated that the order in which the proton and hydride are delivered could be reversed in FLP reductions of a series of nitro-olefins. Alcarazo and coworkers 37 used B(C 6 F 5 ) 3 and a N-base to catalytically hydrogenate allenic esters and Paradies' group used B/P FLPs to hydrogenate enones. 38 Soos showed that B(C 6 F 5 ) 3 and DABCO catalytically reduce imines, enamines and N-heterocycles.…”

Section: Flp Hydrogenationsmentioning

confidence: 99%

Frustrated Lewis Pairs

2015

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The articulation of the notion of "frustrated Lewis pairs" (FLPs), which emerged from the discovery that H2 can be reversibly activated by combinations of sterically encumbered Lewis acids and bases, has prompted a great deal of recent activity. Perhaps the most remarkable consequence has been the development of FLP catalysts for the hydrogenation of a range of organic substrates. In the past 9 years, the substrate scope has evolved from bulky polar species to include a wide range of unsaturated organic molecules. In addition, effective stereoselective metal-free hydrogenation catalysts have begun to emerge. The mechanism of this activation of H2 has been explored, and the nature and range of Lewis acid/base combinations capable of effecting such activation have also expanded to include a variety of non-metal species. The reactivity of FLPs with a variety of other small molecules, including olefins, alkynes, and a range of element oxides, has also been developed. Although much of this latter chemistry has uncovered unique stoichiometric transformations, metal-free catalytic hydroamination, CO2 reduction chemistry, and applications in polymerization have also been achieved. The concept is also beginning to find applications in bioinorganic and materials chemistry as well as heterogeneous catalysis. This Perspective highlights many of these developments and discusses the relationship between FLPs and established chemistry. Some of the directions and developments that are likely to emerge from FLP chemistry in the future are also presented.

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“…replaced with as econdary or tertiary ammonium or phosphonium chloride 4-6 (Scheme 2, bottom), the corresponding triarylborohydrides 7,w hich were previously synthesized by the cleavage of H 2 by FLPs, [5,6] were obtained in good yield in analytically pure form.…”

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confidence: 99%

Scope and Mechanisms of Frustrated Lewis Pair Catalyzed Hydrogenation Reactions of Electron‐Deficient CC Double Bonds

2015

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Several phosphonium and ammonium triarylborohydrides, which are intermediates in hydrogenation reactions catalyzed by frustrated Lewis pairs, were synthesized in high yield under mild conditions from triaryl boranes, ammonium or phosphonium halides, and triethylsilane. The kinetics and mechanisms of the reactions of these hydridoborate salts with benzhydrylium ions, iminium ions, quinone methides, and Michael acceptors were investigated, and their nucleophilicity was determined and compared with that of other hydride donors.

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Metal‐Free Hydrogenation of Electron‐Poor Allenes and Alkenes

Cited by 97 publications

References 50 publications

Frustrated Lewis Pair Chemistry: Development and Perspectives

Frustrated Lewis Pair Chemistry: Development and Perspectives

Frustrated Lewis Pairs

Scope and Mechanisms of Frustrated Lewis Pair Catalyzed Hydrogenation Reactions of Electron‐Deficient CC Double Bonds

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