A C2-symmetric nickel diamine complex as an asymmetric catalyst for enecarbamate additions to butane-2,3-dione

Fossey, John S.; Matsubara, Ryosuke; Vital, Paulo; Kobayashi, Shū

doi:10.1039/b505404d

Cited by 42 publications

(24 citation statements)

References 16 publications

(2 reference statements)

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“…2b). In contrast to chiral nickel(II)–diamine catalysts identified so far7891011 (Supplementary Figs 3–5), the newly developed complexes are chiral-at-Ni(II) center1920212223, in which the initial C 2 -symmetry of the ligands on I and II is desymmetrized through formation of the Ni(II) complex. Mononuclear Ni(II) complex I has a distorted octahedral architecture; the atomic distance between Ni(II) and N(2) (2.109(1) Å) is longer than that of Ni(II)–N(1) (2.091(1) Å), and the N(2)–Ni(II)–O(4) angle is 155.99(5)°, which differs markedly from 180°; we show the longer Ni(II)–N(2) bond in pseudoapical position in Fig.…”

Section: Resultsmentioning

confidence: 69%

“…Several examples of chiral nickel complexes that act as asymmetric catalysts have been sporadically characterized by X-ray structure analysis, opening up a window of opportunity to discuss the stereo-discrimination process in asymmetric nickel catalysis7891011121314151617. Evans's transition-state model, which was proposed on the basis of X-ray analysis of the Ni(II)–diamine–enolate complex, is a remarkable example, explaining the stereochemical course in the catalytic asymmetric Michael reaction of nitroolefins with 1,3-dicarbonyl compounds78.…”

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confidence: 99%

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Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

et al. 2017

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Chiral metal catalysts have been widely applied to asymmetric transformations. However, the electronic structure of the catalyst and how it contributes to the activation of the substrate is seldom investigated. Here, we report an empirical approach for providing insights into the catalytic activation process in the distorted Ni(II)-catalysed asymmetric [3+2] cycloaddition of α-ketoesters. We quantitatively characterize the bonding nature of the catalyst by means of electron density distribution analysis, showing that the distortion around the Ni(II) centre makes the dz2 orbital partially ‘naked', wherein the labile acetate ligand is coordinated with electrostatic interaction. The electron-deficient dz2 orbital and the acetate act together to deprotonate the α-ketoester, generating the (Λ)-Ni(II)–enolate. The solid and solution state analyses, together with theoretical calculations, strongly link the electronic structure of the centrochiral octahedral Ni(II) complex and its catalytic activity, depicting a cooperative mechanism of enolate binding and outer sphere hydrogen-bonding activation.

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Section: Resultsmentioning

confidence: 69%

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confidence: 99%

Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

et al. 2017

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“…(23); Cbz = carbobenzyloxy]. [87] The monomeric aquanickel(II) complex 83, whose structure was established by X-ray crystallography, could be the catalyst precursor. [88] The strong (+)-NLE was tentatively attributed to the formation of ineffective heterochiral [NiL 2 ] complex.…”

Section: Reviews 466mentioning

confidence: 99%

Nonlinear Effects in Asymmetric Catalysis

Satyanarayana¹,

Abraham²,

Kagan³

2008

Angew Chem Int Ed

489

273

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There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non-enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis.

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“…[9][10][11][12] Copper(II)-amine complexes have been used as catalysts in the oxidative polymerization of phenol derivatives, [13][14][15][16] hydrolysis of organophosphate esters, 17 O-arylation reaction of phenols, 18 and epoxidation reaction. 19 For nickel(II)-amine complexes, they were employed as a catalyst for enecarbamate additions to butane-2,3-dione 20 and as a catalyst for alkane hydroxylation with meta-chloroperoxybenzoic acid (m-CPBA). 21 The objectives of this work was to synthesize metal-ethylenediamine complexes [M(en) 2 's] and metal-triethylenetetramine complexes [M(trien)'s], where M ¼ Cu or Ni, and use them as catalysts for RPUR foam preparation.…”

Section: Introductionmentioning

confidence: 99%

Copper–amine complexes as new catalysts for rigid polyurethane foam preparations

Pengjam¹,

Saengfak²,

Ekgasit³

et al. 2011

J of Applied Polymer Sci

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A new class of catalyst for the preparation of rigid polyurethane (RPUR) foams was developed. Metal(II)-amine complexes [M(en) 2 and M(trien), where M ¼ Cu or Ni, en ¼ ethylenediamine, and trien ¼ triethylenetetramine] were synthesized and used as catalysts in the preparation of RPUR foams. The catalytic activity of the metal(II)-amine complexes and properties of the RPUR foams were investigated and compared to those prepared by N,N-dimethylcyclohexylamine (DMCHA), which is a common commercial tertiary amine catalyst used in the preparation of RPUR foams. The use of M(en) 2 and M(trien) can improve the working environment in RPUR foam processing because DMCHA and other commercial tertiary amine catalysts have a strong odor, whereas M(en) 2 and M(trien) do not have any odor. The reaction times in RPUR foam preparation, namely, cream time, gel time, tack-free time, and rise time, were investigated. These data indicated that the copper-ethylenediamine complex [Cu(en) 2 ] and copper-triethylenetetramine complex [Cu(trien)] had comparable catalytic activity to DMCHA, whereas the catalytic activity of the nickel complexes was not good. Attenuated total reflection-IR spectroscopy of the RPUR foams prepared with Cu(en) 2 and Cu(trien) showed quantitative isocyanate (NCO) conversion. The density and compressive strength of the RPUR foams prepared from Cu(en) 2 and Cu(trien) were comparable to those prepared from DMCHA.

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A C2-symmetric nickel diamine complex as an asymmetric catalyst for enecarbamate additions to butane-2,3-dione

Cited by 42 publications

References 16 publications

Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

Nonlinear Effects in Asymmetric Catalysis

Copper–amine complexes as new catalysts for rigid polyurethane foam preparations

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