Ni- and Pd-Catalyzed Enantioselective 1,2-Dicarbofunctionalization of Alkenes

Synthesis, Год журнала: 2023, Номер 56(01), С. 1 - 15

Опубликована: Июнь 12, 2023

Abstract Catalytic enantioselective 1,2-dicarbofunctionalization (1,2-DCF) of alkenes is a powerful transformation growing importance in organic synthesis for constructing chiral building blocks, bioactive molecules, and agrochemicals. Both two- three-component context, this family reactions generates densely functionalized, structurally complex products single step. Across several distinct mechanistic pathways at play these transformations with nickel or palladium catalysts, stereocontrol can be obtained through tailored ligands. In Review we discuss the various strategies, mechanisms, catalysts that have been applied to achieve enantioinduction alkene 1,2-DCF. 1 Introduction 2 Two-Component Enantioselective 1,2-DCF via Migratory Insertion 3 Radical Capture 4 Three-Component 5 6 Miscellaneous Mechanisms 7 Conclusion

Язык: Английский

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Ligand Redox Activity of Organonickel Radical Complexes Governed by the Geometry

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(37), С. 20551 - 20561

Опубликована: Сен. 11, 2023

Nickel-catalyzed cross-coupling reactions often employ bidentate π-acceptor N-ligands to facilitate radical pathways. This report presents the synthesis and characterization of a series organonickel complexes supported by N-ligands, including bpy, phen, pyrox, which are commonly proposed observed intermediates in catalytic reactions. Through comparison relevant analogues, we have established an empirical rule governing electronic structures these nickel complexes. The exhibit redox activity four-coordinate, square-planar complexes, leading observation ligand-centered radicals. In contrast, ligands do not display when supporting three-coordinate, trigonal planar better described as nickel-centered trend holds true irrespective nature actor ligands. These results provide insights into beneficial effect coordinating salt additives solvents stabilizing during modulating Understanding active can contribute development optimization catalysts for

Язык: Английский

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Mechanism of Ni-Catalyzed Photochemical Halogen Atom-Mediated C(sp³)–H Arylation

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(22), С. 15331 - 15344

Опубликована: Май 23, 2024

Within the context of Ni photoredox catalysis, halogen atom photoelimination from has emerged as a fruitful strategy for enabling hydrogen transfer (HAT)-mediated C(sp3)–H functionalization. Despite numerous synthetic transformations invoking this paradigm, unified mechanistic hypothesis that is consistent with experimental findings on catalytic systems and accounts radical formation facile C(sp2)–C(sp3) bond remains elusive. We employ kinetic analysis, organometallic synthesis, computational investigations to decipher mechanism prototypical Ni-catalyzed photochemical arylation reaction. Our revise previous proposals, first by examining relevance SET EnT processes intermediates relevant HAT-based investigation highlights ability blue light promote efficient Ni–C(sp2) homolysis cationic NiIII reductive elimination bipyridine NiII complexes. However interesting, rates selectivities these do not account productive pathway. Instead, our studies support involves evolution in situ generated dihalide intermediates, capture NiII(aryl)(halide) resting state, key C–C NiIII. Oxidative addition NiI, opposed Ni0, rapid NiIII/NiI comproportionation play roles process. The presented herein offer fundamental insight into reactivity broader catalysis.

Язык: Английский

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A decarbonylative approach to alkylnickel intermediates and C(sp ³ )-C(sp ³ ) bond formation

Science, Год журнала: 2024, Номер 385(6715), С. 1331 - 1337

Опубликована: Сен. 19, 2024

The myriad nickel-catalyzed cross-coupling reactions rely on the formation of an organonickel intermediate, but limitations in forming monoalkylnickel species have limited options for C(sp 3 ) cross-coupling. monoalkylnickel(II) from abundant carboxylic acid esters would be valuable, derivatives are primarily decarboxylated to form alkyl radicals that lack correct reactivity. In this work, we disclose a facile oxidative addition and decarbonylation sequence forms intermediates through nonradical process. key ligand, bis(4-methylpyrazole)pyridine, accelerates decarbonylation, stabilizes alkylnickel(II) destabilizes off-cycle nickel(0) carbonyl species. utility new reactivity )-C(sp bond is demonstrated reaction challenging by purely radical methods—the selective primary with iodides.

Язык: Английский

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Cross-Electrophile Coupling: Principles, Methods, and Applications in Synthesis

Chemical Reviews, Год журнала: 2024, Номер unknown

Опубликована: Ноя. 26, 2024

Cross-electrophile coupling (XEC), defined by us as the cross-coupling of two different σ-electrophiles that is driven catalyst reduction, has seen rapid progression in recent years. As such, this review aims to summarize field from its beginnings up until mid-2023 and provide comprehensive coverage on synthetic methods current state mechanistic understanding. Chapters are split type bond formed, which include C(sp

Язык: Английский

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Enantioselective Directed Nickel-Catalyzed Three-Component Reductive Arylalkylation of Alkenes via the Carbometalation/Radical Cross-Coupling Sequence

ACS Catalysis, Год журнала: 2024, Номер 14(7), С. 4395 - 4406

Опубликована: Март 8, 2024

Asymmetric reductive three-component arylalkylation of alkenes via the radical relay method has been well established, while asymmetric migratory insertion strategy remains unexplored. We report enantioselective nickel-catalyzed cross-electrophile with aryl- and alkyl halides an integrated Heck carbometalation/radical cross-coupling sequence. This protocol employing a chiral Ni/PHOX catalytic system allows terminal internal to successfully engage exquisite control regio-, chemo-, stereoselectivity. More importantly, this undergoes regio- arylnickelation followed by Csp3–Csp3 elimination, thus exhibiting reverse regioselectivity method. Mild reaction conditions exceptional functional group tolerance facilitate method's compatibility bioactive motifs modular synthesis biologically active compounds. The experiments density theory calculations provide insights into mechanism origin stereoselectivity, hemilabile nature PHOX ligand is critical for achieving arylalkylation.

Язык: Английский

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Effect of 6,6′-Substituents on Bipyridine-Ligated Ni Catalysts for Cross-Electrophile Coupling

ACS Catalysis, Год журнала: 2024, Номер 14(9), С. 6897 - 6914

Опубликована: Апрель 19, 2024

A family of 4,4′-tBu2-2,2′-bipyridine (tBubpy) ligands with substituents in either the 6-position, 4,4′-tBu2-6-Me-bpy (tBubpyMe), or 6 and 6′-positions, 4,4′-tBu2-6,6′-R2-bpy (tBubpyR2; R = Me, iPr, sBu, Ph, Mes), was synthesized. These were used to prepare Ni complexes 0, I, II oxidation states. We observed that 6′-positions tBubpy ligand impact properties complexes. For example, bulkier 6,6′-positions better stabilized (tBubpyR2)NiICl species resulted a cleaner reduction from (tBubpyR2)NiIICl2. However, hindered prevented coordination tBubpyR2 Ni0(cod)2. In addition, by using type (tBubpyMe)NiCl2 (tBubpyR2)NiCl2 as precatalysts for different XEC reactions, we demonstrated 6,6′-substituents lead major differences catalytic performance. Specifically, while (tBubpyMe)NiIICl2 is one most active catalysts reported date can facilitate reactions at room temperature, lower turnover frequencies containing ligands. detailed study on intermediates (tBubpy)Ni(Ar)I (tBubpyMe2)Ni(Ar)I revealed several factors likely contributed activity. whereas are low spin relatively stable, high-spin less stable. Furthermore, captures primary benzylic alkyl radicals more slowly than (tBubpy)Ni(Ar)I, consistent activity former catalysis. Our findings will assist design tailor-made Ni-catalyzed transformations.

Язык: Английский

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Reductive alkyl-alkyl coupling from isolable nickel-alkyl complexes

Nature, Год журнала: 2024, Номер 634(8034), С. 585 - 591

Опубликована: Авг. 29, 2024

Язык: Английский

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Light Activation and Photophysics of a Structurally Constrained Nickel(II)–Bipyridine Aryl Halide Complex

Inorganic Chemistry, Год журнала: 2024, Номер 63(9), С. 4120 - 4131

Опубликована: Фев. 20, 2024

Transition-metal photoredox catalysis has transformed organic synthesis by harnessing light to construct complex molecules. Nickel(II)–bipyridine (bpy) aryl halide complexes are a significant class of cross-coupling catalysts that can be activated via direct excitation. This study investigates the effects molecular structure on photophysics these considering an underexplored, structurally constrained Ni(II)–bpy in which and bpy ligands covalently tethered alongside traditional unconstrained complexes. Intriguingly, is photochemically stable but features reversible Ni(II)–C(aryl) ⇄ [Ni(I)···C(aryl)•] equilibrium upon photoexcitation. When electrophile introduced during photoirradiation, we demonstrate preference for photodissociation over recombination, rendering parent Ni(II) source reactive Ni(I) intermediate. Here, characterize photochemical behavior kinetic analyses, quantum chemical calculations, ultrafast transient absorption spectroscopy. Comparison previously characterized indicates structural constraints considered here dramatically influence excited state relaxation pathway provide insight into characteristics excited-state Ni(II)–C bond homolysis radical reassociation dynamics. enriches understanding offers new possibilities designing customized photoactive precise synthesis.

Язык: Английский

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Chemo- and Regioselective Nickel-Catalyzed Reductive 1,4-Alkylarylation of 1,3-Enynes through an L₂NiAr Intermediate

ACS Catalysis, Год журнала: 2024, Номер 14(11), С. 8996 - 9007

Опубликована: Май 28, 2024

Three-component reductive dicarbofunctionalization reactions of 1,3-enynes have been rarely reported because the intricate control chemo- and regioselectivity required, coupled with a limited understanding radical catalytic species involved. Herein, we report nickel-catalyzed 1,4-alkylarylation method for to yield tri- tetrasubstituted allenes using readily accessible alkyl aryl iodides, featuring simple operational protocol mild reaction conditions. In our mechanistic studies, formation propargyl/allenyl was substantiated by isolation propargyl dimer, detection corresponding TEMPO–radical adduct, probe experiments. Two reduced L2NiAr complexes, expected act as intermediates, were generated characterized EPR spectroscopy NiI complexes. The stoichiometric L2Ni(p-NCC6H4) 1,3-enyne iodide showed conversion into dimer allene, suggesting that encompasses same key steps reaction, i.e., activation iodide, generation radical, selective coupling this component.

Язык: Английский

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