Catalytic σ-Bond Metathesis

Reznichenko, A. L.; Hultzsch, Kai C.

doi:10.1007/430_2010_17

Cited by 38 publications

(12 citation statements)

References 212 publications

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“…While aminopentenes 3a – d and aminohexene 5 were commonly cyclized smoothly at room temperature using 2 mol % catalyst loading, aminoheptene 7 required higher catalytic loadings and elevated temperatures to generate azepane 8 (Table ). As has been commonly observed, , the hydroamination/cyclization reaction rates decreased with increasing sizes of heterocyclic rings: 5 > 6 ≫ 7. For example, the turnover frequencies in the hydroamination using ( R )- 2b - Y decreased in the following sequence: aminopentene 3a (750 h –1 at 25 °C) > aminohexene 5 (6.5 h –1 at 25 °C) ≫ aminoheptene 7 (0.17 h –1 at 80 °C) (Table , entry 3; Table , entries 3 and 16).…”

Section: Resultssupporting

confidence: 91%

“…Therefore, catalytic methods for the preparation of amines are highly desirable. The hydroamination reaction − represents a highly attractive process in which an amine N–H functionality is added to an unsaturated carbon–carbon linkage, because it is 100% atom economical without formation of any waste byproduct. As many of the targeted amine products are chiral, the development of chiral catalyst systems for asymmetric hydroamination reactions has been the focus of a large number of studies over the last two decades .…”

Section: Introductionmentioning

confidence: 99%

“…We and others have reported catalyst systems that exceed 90% ee in intramolecular hydroamination reactions of aminoalkenes . However, intermolecular hydroamination reactions remain highly challenging, ,,, especially when they are carried out in a stereoselective manner. Most studies focused on activated or strained alkene substrates, such as vinylarenes, 1,3-dienes, and norbonene, generally applied to amines with low nucleophilicity, such as anilines, carboxamides, sulfonamides, and other protected amines .…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes

et al. 2018

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The series of novel 3,3′-bis(trisarylsilyl)-and 3,3′-bis(arylalkylsilyl)-substituted binaphtholate rare-earthmetal complexes 2a−i (SiR 3 = Si(o-biphenylene)Ph (a), SiCyPh 2 (b), Si-t-BuPh 2 (c), Si(i-Pr) 3 (d), SiCy 2 Ph (e), Si(2-tolyl)Ph 2 (f), Si(4-t-Bu-C 6 H 4 ) 3 (g), Si(4-MeO-C 6 H 4 )Ph 2 (h), SiBnPh 2 (i)) have been prepared via arene elimination from [Ln(o-C 6 H 4 CH 2 NMe 2 ) 3 ] (Ln = Y, Lu) and the corresponding 3,3′-bis(silyl)-substituted binaphthol. The complexes exhibit high catalytic activity in the hydroamination/ cyclization of aminoalkenes, with activities exceeding 1000 h −1 for (R)-2f-Ln, (R)-2g-Ln, and (R)-2h-Ln in the cyclization of 2,2-diphenylpent-4-enylamine (3a) at 25 °C, while the rigid dibenzosilole-substituted complexes (R)-2a-Ln and the triisopropylsilyl-substituted complexes (R)-2d-Ln exhibited the lowest activity in the range of 150−270 h −1 . Catalysts (R)-2b-Lu, (R)-2c-Lu, (R)-2f-Lu, and (R)-2i-Lu provide the highest selectivities for the majority of the substrates, while the yttrium congeners are usually less selective. The highest enantioselectivities of 96% ee were observed using (R)-2a-Lu and (R)-2c-Lu in the cyclization of (4E)-2,2,5-triphenylpent-4-enylamine (9). The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, with some reactions exhibiting a slightly accelerated rate at high conversion due to a shift in the equilibrium between a less active, higher coordinate catalyst species in favor of a more active, lower coordinate species as a result of weaker binding of the hydroamination product in comparison to the aminoalkene substrate. The shift in equilibrium from the higher to the lower coordinate species is also entropically favored at elevated temperatures, which results in an unusual increase in selectivity in the cyclization of 2,2-dimethylpent-4-enylamine (3d), presumably due to a higher selectivity of the lower coordinate catalyst species. All binaphtholate yttrium complexes, except (R)-2a-Y, are catalytically active in the intermolecular hydroamination of benzylamines with terminal alkenes. The highest selectivity of 66% ee was observed for the reaction of benzylamine with 4-phenyl-1-butene using (R)-2h-Y at 110 °C.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes

et al. 2018

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“…Intramolecular hydrophosphination of alkynes catalyzed by trivalent lanthanides was reported 15 years ago by Marks et al − The first intermolecular version using divalent lanthanides followed soon thereafter . Ever since, there is an increasing interest in the hydrophosphination catalyzed by di- and trivalent lanthanide complexes. − The recent development was covered by some review articles. − …”

Section: Introductionmentioning

confidence: 99%

Homoleptic Chiral Benzamidinate Complexes of the Heavier Alkaline Earth Metals and the Divalent Lanthanides

Gamer

Roesky

2016

Organometallics

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Reaction of the chiral amidine N,N′-bis(1-phenylethyl)benzamidine ((S)-HPEBA), KCH(SiMe3)2, and MI2 (M = Ca, Sr, Ba) or LnI2 (Ln = Eu, Yb) in a 2:2:1 stoichiometric ratio resulted in the chiral homoleptic monomeric alkaline earth metal compounds [Ca(PEBA)2(THF)2] (1) and [Sr(PEBA)2(THF)2] (2), the dimeric barium complex [Ba(PEBA)2]2 (3), and the monomeric divalent lanthanide compounds [Eu(PEBA)2(THF)2] (4), and [Yb(PEBA)2(THF)2] (5). The solid-state structures of all compounds were established by single-crystal X-ray diffraction. Three different structures are observed in the solid state. Compounds 1, 2, 4, and 5 form distorted coordination octahedra. For the alkaline earth element complexes 1 and 2, the two THF molecules are located in a trans-position, whereas, for the lanthanide compounds 4 and 5, they are arranged in a cis-position. In contrast, the barium complex 3 is dimeric with two amidinate ligands in an unusual “side-on” bridging mode. All five complexes were used as catalysts for hydrophosphination reactions of styrene and substituted analogues.

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“…Organophosphines are ubiquitous with transition metal chemistry and have a prominent role in homogenous and asymmetric catalysis as well as in medicinal chemistry. [1][2][3]4 Moreover, organophosphines are also of significant interest as derivatives to phosphonium-based ionic liquids (ILs). Phosphonium ILs exhibit higher thermal stabilities and conductivities when compared to their corresponding ammonium IL counterparts, [5][6][7][8][9][10] are an attractive alternative class of solvents to more traditional volatile organic compounds, 11,12 can be used for gas capture 13 and demonstrate antimicrobial properties.…”

Section: Introductionmentioning

confidence: 99%

Hydrophosphination of Styrene and Polymerization of Vinylpyridine: A Computational Investigation of Calcium-Catalyzed Reactions and the Role of Fluxional Noncovalent Interactions

Ward

Hunt

2016

ACS Catal.

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A computational investigation of the intermolecular hydrophosphination of styrene and 2-vinylpyridine, catalysed by the heteroleptic b-diketiminato-stabilised calcium complex [(PhNC(Me)CHC(Me)NPh)CaPPh2], is presented. Alkene insertion does not proceed via the traditional route as proposed by experimental and theoretical research related to intermolecular hydroamination catalysed by alkaline earth or lanthanide complexes. In contrast, for the hydrophosphination mechanism, insertion proceeds via an outer sphere, conjugative addition where there is no direct interaction of Ca with the vinyl functionality. Following the initial rate determining alkene insertion, two distinct mechanisms emerge, protonolysis or polymerisation. Polymerisation of styrene is energetically less favourable than protonolysis whereas the reverse is determined for 2-vinylpyridine, thereby providing strong evidence for outcomes observed experimentally. The vinylarene ring is important as it allows for preferential coordination of the unsaturated substrate through numerous non-covalent Ca···π, CH···π and CaE (E=P, N) interactions, moreover the vinylarene ring counteracts unfavourable charge localisation within the activated transition state. The additional stability of the CaN over CaP dative interaction in vinylpyridine provides a rationalisation for the experimentally observed enhanced reactivity of vinylpyridine, particularly in the context of the almost identical local alkene insertion barriers. Previously, little emphasis has been placed on the involvement of non-covalent interactions however, our calculations reveal that Ca···π, CH···π and Cadonor interactions are critical; stabilising key intermediates and transition states, while also introducing numerous competitive pathways.

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Catalytic σ-Bond Metathesis

Cited by 38 publications

References 212 publications

Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes

Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes

Homoleptic Chiral Benzamidinate Complexes of the Heavier Alkaline Earth Metals and the Divalent Lanthanides

Hydrophosphination of Styrene and Polymerization of Vinylpyridine: A Computational Investigation of Calcium-Catalyzed Reactions and the Role of Fluxional Noncovalent Interactions

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