Nickel‐Catalyzed Dehydrogenative Couplings

Arun, V.; Mahanty, Kingshuk; Sarkar, Suman De

doi:10.1002/cctc.201900254

Cited by 39 publications

(15 citation statements)

References 114 publications

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“…Heck reaction coupled to a transfer hydrogenation process 36–44 . We envisioned that selectivity for this pathway over other alternatives could be achieved by tuning the coordination environment around nickel with an appropriate phosphine ligand and directing group 45–52 . Herein we describe the realization of this goal.…”

Section: Introductionmentioning

confidence: 99%

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

Kang

Zhou

et al. 2019

Nat Commun

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The conventional oxidative Heck reaction between aryl boronic acids and alkenes typically involved the PdII/Pd0/PdII catalytic cycle incorporating an external oxidant and often suffered C=C bond isomerization for internal alkyl-substituted alkenes via chain-walking. Herein, we demonstrate that the regioselectivity (γ-selectivity vs. δ-selectivity) and pathway selectivity (hydroarylation vs. oxidative Heck coupling) of a directed Ni-catalyzed alkene arylation can be controlled by judicious tuning of the coordination environment around the nickel catalyst via optimization of an appropriate phosphine ligand and directing group. In this way, the Ni(0)-catalyzed oxidative Heck arylation that relies on transfer hydrogenation of an acceptor olefin is developed with excellent E/Z selectivity and regioselectivity. Mechanistic investigations suggest that the addition of the acceptor is crucial for lowering the energy for carbometalation and for enabling catalytic turnover.

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Section: Introductionmentioning

confidence: 99%

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

Kang

Zhou

et al. 2019

Nat Commun

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“…Quinoline derivatives are considered to be one of the important class of heterocycle compounds, , and we were pleased to notice that the present protocol is also suited for the synthesis of quinoline. Various substituted quinolines were attained via the oxidative coupling of 2-aminobenzyl alcohol with several ketones via an acceptorless dehydrogenation process (Table ).…”

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confidence: 99%

[(PPh₃)₂NiCl₂]-Catalyzed C–N Bond Formation Reaction via Borrowing Hydrogen Strategy: Access to Diverse Secondary Amines and Quinolines

2021

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Commercially available [(PPh3)2NiCl2] was found to be an efficient catalyst for the mono-N-alkylation of (hetero)aromatic amines, employing alcohols to deliver diverse secondary amines, including the drug intermediates chloropyramine (5b) and mepyramine (5c), in excellent yields (up to 97%) via the borrowing hydrogen strategy. This method shows a superior activity (TON up to 10000) with a broad substrate scope at a low catalyst loading of 1 mol % and a short reaction time. Further, this strategy is also successful in accessing various quinoline derivatives following the acceptorless dehydrogenation pathway.

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“…Ni complexes have been shown to catalyze some types of dehydrogenative couplings, such as aromatic alkynylation . Ni-catalyzed systems that mediate dehydrogenative aryl–aryl coupling are rare, with only a few reported examples with Ni II salts .…”

Section: Introductionmentioning

confidence: 99%

Nickel-Mediated Dehydrogenative Aryl–Aryl Homocoupling of a Bulky Phosphino-Pyridine

2019

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Aryl−aryl bond formation through dehydrogenative coupling is an attractive transformation due to the atom and step economy of working with unfunctionalized C−H bonds. Pd catalysts are most common for this process, but Ni complexes have also been targeted as less expensive and more abundant alternatives. Here we report the ability of Ni 0 to activate a sterically encumbered phosphino-pyridine ligand with resulting dehydrogenative aryl−aryl homocoupling. The net H 2 equivalent is transferred to the coligand, resulting in hydrogenation of an olefin unit. We have investigated the mechanism of this process by stirring Ni(1,5-COD) 2 (COD = cyclooctadiene) and the PNPh ligand (PNPh = 2-((di-tert-butylphosphino)methyl)-6phenylpyridine) at mild temperatures to afford a Ni II complex. Isolation and characterization shows a PNPh ligand coordinated to Ni II through an activated pyridine carbon and the directing phosphine. The coligand is an activated allylic cyclooctenyl fragment resulting from partial hydrogenation of 1,5-COD. We propose that this intermediate reacts intermolecularly with 1 equiv of itself, enabling the isolation of a bi-PNPh compound (bi-PNPh = 2,2′-bis((di-tert-butylphosphino)methyl)-6,6′diphenyl-3,3′-bipyridine), coupled through the activated pyridyl position. This dehydrogenative coupling, although stoichiometric, demonstrates the potential of Ni 0 -mediated C(sp 2 )−H activation and homocoupling for synthetic applications.

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Nickel‐Catalyzed Dehydrogenative Couplings

Cited by 39 publications

References 114 publications

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

[(PPh₃)₂NiCl₂]-Catalyzed C–N Bond Formation Reaction via Borrowing Hydrogen Strategy: Access to Diverse Secondary Amines and Quinolines

Nickel-Mediated Dehydrogenative Aryl–Aryl Homocoupling of a Bulky Phosphino-Pyridine

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Nickel‐Catalyzed Dehydrogenative Couplings

Cited by 39 publications

References 114 publications

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation

[(PPh3)2NiCl2]-Catalyzed C–N Bond Formation Reaction via Borrowing Hydrogen Strategy: Access to Diverse Secondary Amines and Quinolines

Nickel-Mediated Dehydrogenative Aryl–Aryl Homocoupling of a Bulky Phosphino-Pyridine

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[(PPh₃)₂NiCl₂]-Catalyzed C–N Bond Formation Reaction via Borrowing Hydrogen Strategy: Access to Diverse Secondary Amines and Quinolines