Mechanism of Synergistic Cu(II)/Cu(I)-Mediated Alkyne Coupling: Dinuclear 1,2-Reductive Elimination after Minimum Energy Crossing Point

Qi, Xiaotian; Bai, Ruopeng; Zhu, Lei; Jin, Runsen; Lei, Aiwen; Lan, Yu

doi:10.1021/acs.joc.5b02797

Cited by 42 publications

(21 citation statements)

References 85 publications

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“…2). In this case, the energy barrier could be represented by the minimum energy crossing point (MECP)363738, the energy of which plays a significant role in determining the reaction mechanism and selectivity3839404142. Surprisingly, these issues have seldom been discussed in transition metal-catalyzed radical–radical cross-coupling reactions.…”

mentioning

confidence: 99%

Stabilization of Two Radicals with One Metal: A Stepwise Coupling Model for Copper-Catalyzed Radical–Radical Cross-Coupling

Zhu

Bai

et al. 2017

Sci Rep

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Transition metal-catalyzed radical–radical cross-coupling reactions provide innovative methods for C–C and C–heteroatom bond construction. A theoretical study was performed to reveal the mechanism and selectivity of the copper-catalyzed C–N radical–radical cross-coupling reaction. The concerted coupling pathway, in which a C–N bond is formed through the direct nucleophilic addition of a carbon radical to the nitrogen atom of the Cu(II)–N species, is demonstrated to be kinetically unfavorable. The stepwise coupling pathway, which involves the combination of a carbon radical with a Cu(II)–N species before C–N bond formation, is shown to be probable. Both the Mulliken atomic spin density distribution and frontier molecular orbital analysis on the Cu(II)–N intermediate show that the Cu site is more reactive than that of N; thus, the carbon radical preferentially react with the metal center. The chemoselectivity of the cross-coupling is also explained by the differences in electron compatibility of the carbon radical, the nitrogen radical and the Cu(II)–N intermediate. The higher activation free energy for N–N radical–radical homo-coupling is attributed to the mismatch of Cu(II)–N species with the nitrogen radical because the electrophilicity for both is strong.

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confidence: 99%

Stabilization of Two Radicals with One Metal: A Stepwise Coupling Model for Copper-Catalyzed Radical–Radical Cross-Coupling

Zhu

Bai

et al. 2017

Sci Rep

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“…The mechanistic study of Glaser coupling is still ongoing experimentally [55] and theoretically. [56][57][58][59][60] These studies suggest that the proposed intermediates I-IV depend on the valence at the copper metals. Researchersh ave to pay attention to the copperp recatalyst used, which may affect the efficiency of macrocyclization.…”

Section: Synthetic Methodsf or P-conjugated Macrocycles Containing Anmentioning

confidence: 93%

“…By considering that these methods efficiently provide strained macrocyclic structures, two alkyne moieties require nonlinear conformation in the intermediate for the reductive elimination step (Figure b). The mechanistic study of Glaser coupling is still ongoing experimentally and theoretically . These studies suggest that the proposed intermediates I – IV depend on the valence at the copper metals.…”

Section: Synthetic Methods For π‐Conjugated Macrocycles Containing Anmentioning

confidence: 99%

π‐Conjugated Macrocycles Bearing Angle‐Strained Alkynes

Miki

Ohe

2019

Chemistry A European J

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Angle‐strained alkyne‐containing π‐conjugated macrocycles are attractive compounds both in functional materials chemistry and biochemistry. Their interesting reactivity as well as photophysical and supramolecular properties have been revealed in the past three decades. This review highlights the recent advances in angle‐strained alkyne‐containing π‐conjugated macrocycles, especially their synthetic methods, the bond angles of alkynes (∠sp at C≡C−C), and their functions. The theoretical and experimental research on cyclo[n]carbons and para‐cyclophynes consisting of ethynylenes and para‐phenylenes are mainly summarized. Related macrocycles bearing other linkers, such as ortho‐phenylenes, meta‐phenylenes, heteroaromatics, biphenyls, extended aromatics, are also overviewed. Bond angles of strained alkynes in π‐conjugated macrocycles, which are generable, detectable, and isolable, are summarized at the end of this review.

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“…In 2011, Nikonov's group (Gutsulyak et al, 2011) realized hydrosilylation of pyridine with ruthenium as the catalyst at room temperature and obtained a mixture of 1,2- and 1,4-borohydropyridine. However, application of these reactions in synthetic chemistry is greatly limited by the expensive transition metal catalyst (Yaroshevsky, 2006; Dobereiner and Crabtree, 2010; Osakada, 2011; Huang and Xia, 2015; Li et al, 2015; Qi et al, 2016, 2018; Yang et al, 2016; Yu et al, 2016; Xing et al, 2017; Liu et al, 2018; Luo et al, 2018; Zhu et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Role of Alkaline-Earth Metal-Catalyst: A Theoretical Study of Pyridines Hydroboration

Chen

et al. 2019

Front. Chem.

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Density functional theory (DFT) calculations have been performed to investigate the mechanism of alkaline-earth-metal-catalyzed hydroboration of pyridines with borane. In this reaction, the active catalytic species is considered to be an alkaline earth metal hydride complex when the corresponding alkaline earth metal is used as the catalyst. The theoretical results reveal that initiation of the catalytic cycle is hydride transfer to generate a magnesium hydride complex when β-diimine alkylmagnesium is used as a pre-catalyst. The magnesium hydride complex can undergo coordination of the pyridine reactant followed by hydride transfer to form a dearomatized magnesium pyridine intermediate. Coordination of borane and hydride transfer from borohydride to magnesium then give the hydroboration product and regenerate the active magnesium hydride catalyst. The rate-determining step of the catalytic cycle is hydride transfer to pyridine with a free energy barrier of 29.7 kcal/mol. Other alkaline earth metal complexes, including calcium and strontium complexes, were also considered. The DFT calculations show that the corresponding activation free energies for the rate-determining step of this reaction with calcium and strontium catalysts are much lower than with the magnesium catalyst. Therefore, calcium and strontium complexes can be used as the catalyst for the reaction, which could allow mild reaction conditions.

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Mechanism of Synergistic Cu(II)/Cu(I)-Mediated Alkyne Coupling: Dinuclear 1,2-Reductive Elimination after Minimum Energy Crossing Point

Cited by 42 publications

References 85 publications

Stabilization of Two Radicals with One Metal: A Stepwise Coupling Model for Copper-Catalyzed Radical–Radical Cross-Coupling

Stabilization of Two Radicals with One Metal: A Stepwise Coupling Model for Copper-Catalyzed Radical–Radical Cross-Coupling

π‐Conjugated Macrocycles Bearing Angle‐Strained Alkynes

Role of Alkaline-Earth Metal-Catalyst: A Theoretical Study of Pyridines Hydroboration

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