<i>C</i><sub>2</sub>-Symmetric Dinickel Catalysts for Enantioselective [4 + 1]-Cycloadditions

Behlen, Michael J.; Uyeda, Christopher

doi:10.1021/jacs.0c08262

Cited by 23 publications

(13 citation statements)

References 49 publications

(19 reference statements)

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“…52 We found that chiral napthyridine−bis(oxazoline) ligands (napbox) could be prepared and subsequently metalated to form (napbox)Ni 2 (OAc) complexes. 53 Complex 21 is an effective catalyst for enantioselective, intermolecular [4 + 1]-cycloaddition reactions, providing ee values of up to 98%.…”

Section: Vinylidene Transfermentioning

confidence: 99%

“…Substituted oxazolines are commonly used in chiral ligands for asymmetric catalysis but have not been widely incorporated into binucleating ligand frameworks (Figure C) . We found that chiral napthyridine–bis(oxazoline) ligands (napbox) could be prepared and subsequently metalated to form (napbox)Ni 2 (OAc) complexes . Complex 21 is an effective catalyst for enantioselective, intermolecular [4 + 1]-cycloaddition reactions, providing ee values of up to 98%.…”

Section: Stoichiometric Reactivity and Catalysismentioning

confidence: 99%

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Dinickel Active Sites Supported by Redox-Active Ligands

Uyeda

Farley

2021

Acc. Chem. Res.

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Conspectus Redox reactions that take place in enzymes and on the surfaces of heterogeneous catalysts often require active sites that contain multiple metals. By contrast, there are very few homogeneous catalysts with multinuclear active sites, and the field of organometallic chemistry continues to be dominated by the study of single metal systems. Multinuclear catalysts have the potential to display unique properties owing to their ability to cooperatively engage substrates. Furthermore, direct metal-to-metal covalent bonding can give rise to new electronic configurations that dramatically impact substrate binding and reactivity. In order to effectively capitalize on these features, it is necessary to consider strategies to avoid the dissociation of fragile metal–metal bonds in the course of a catalytic cycle. This Account describes one approach to accomplishing this goal using binucleating redox-active ligands. In 2006, Chirik showed that pyridine–diimines (PDI) have sufficiently low-lying π* levels that they can be redox-noninnocent in low-valent iron complexes. Extending this concept, we investigated a series of dinickel complexes supported by naphthyridine–diimine (NDI) ligands. These complexes can promote a broad range of two-electron redox processes in which the NDI ligand manages electron equivalents while the metals remain in a Ni(I)–Ni(I) state. Using (NDI)Ni2 catalysts, we have uncovered cases where having two metals in the active site addresses a problem in catalysis that had not been adequately solved using single-metal systems. For example, mononickel complexes are capable of stoichiometrically dimerizing aryl azides to form azoarenes but do not turn over due to strong product inhibition. By contrast, dinickel complexes are effective catalysts for this reaction and avoid this thermodynamic sink by binding to azoarenes in their higher-energy cis form. Dinickel complexes can also activate strong bonds through the cooperative action of both metals. Norbornadiene has a ring-strain energy that is similar to that of cyclopropane but is not prone to undergoing C–C oxidative addition with monometallic complexes. Using an (NDI)Ni2 complex, norbornadiene undergoes rapid ring opening by the oxidative addition of the vinyl and bridgehead carbons. An inspection of the resulting metallacycle reveals that it is stabilized through a network of secondary Ni−π interactions. This reactivity enabled the development of a catalytic carbonylative rearrangement to form fused bicyclic dienones. These vignettes and others described in this Account highlight some of the implications of metal–metal bonding in promoting a challenging step in a catalytic cycle or adjusting the thermodynamic landscape of key intermediates. Given that our studies have focused nearly exclusively on the (NDI)Ni2 system, we anticipate that many more such cases are left to be discovered as other transition-metal combinations and ligand classes are explored.

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Section: Vinylidene Transfermentioning

confidence: 99%

Section: Stoichiometric Reactivity and Catalysismentioning

confidence: 99%

Dinickel Active Sites Supported by Redox-Active Ligands

Uyeda

Farley

2021

Acc. Chem. Res.

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“…To complete the coordination sphere of the nickels, a benzene was introduced as a π-bridging ligand (Figure I.4a). 36 This specific complexes can promote a large variety of cyclisations [37][38][39][40][41][42][43] like alkyne cyclotrimerisation, [4+1] cycloaddition of diene, cyclopropanation and the Pauson-Khand reaction. The groups of Bera 44 and Tilley, 45 45 In naphthyridine complexes, the C-H reaction can occur on the naphthyridine ligand itself or on another reactant coordinated to the metal(s).…”

Section: -Introduction 1 -Naphthyridine Based Complexesmentioning

confidence: 99%

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

et al. 2021

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Two unsymmetrical dinucleating naphthyridine-based ligands with di(pyridyl) and phosphino side arms were employed in the synthesis of dicopper(I) chloride cores that activate NaBPh 4 to afford bridging phenyl organocopper complexes. In these compounds, the bridging ligand binds symmetrically, as observed in previously described symmetrical dicopper(I) complexes supported by naphthyridine-based ligands with two di(pyridyl) side arms. Unlike the symmetrical systems, however, these complexes undergo quasireversible electrochemical reductions, and chemical reduction yields a diamagnetic product resulting from the coupling of naphthyridine-based radicals of two complexes. The μ-Ph complexes activate the C−H bonds of terminal alkynes and the electron-poor arene C 6 F 5 H. By DFT calculations, the mechanism of terminal alkyne activation involves H-atom transfer at the cationic dicopper center and is sensitive to subtle changes in copper-ligand interactions as well as the position of the anion.

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“…Moreover, distinct formal (3+2) cycloadditions which have also been useful for the construction of enantioriched cyclopentenes derivatives employed N-heterocyclic carbene (NHC)-catalyzed reactions, [20][21][22] metal carbenoids, 23 and the ring opening of cyclopropanes. [24][25][26] Although less explored, formal (4+1) cycloaddition is also a suitable strategy and, according to the recent literature, [27][28][29] either phosphine 30 and metal-catalyzed 31 are versatile and powerful approaches for the construction of these five membered ring systems. In 2014, Fu and co-workers disclosed a biphenyl phosphine-catalyzed enantioselective (4+1) annulation of allenoates with Michael donors (Scheme 1b).…”

Section: Introductionmentioning

confidence: 99%

“…Although less explored, formal (4 + 1) cycloaddition is also a suitable strategy and, according to recent literature, 27–29 phosphine 30 and metal catalysis 31 are versatile and powerful approaches for the construction of these five membered ring systems. In 2014, Fu and co-workers disclosed a biphenyl phosphine-catalyzed enantioselective (4 + 1) annulation of allenoates with Michael donors ( Scheme 1b ).…”

Section: Introductionmentioning

confidence: 99%