- Long-Lived Charge-Transfer States of Nickel(II) Aryl Halide Complexes Facilitate Bimolecular Photoinduced Electron Transfer
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Here we investigate the photophysics and photochemistry of Ni(II) aryl halide complexes common to cross-coupling and Ni/photoredox reactions. Computational and ultrafast spectroscopic studies reveal that these complexes feature long-lived 3MLCT excited states, implicating Ni as an underexplored alternative to precious metal photocatalysts. Moreover, we show that 3MLCT Ni(II) engages in bimolecular electron transfer with ground-state Ni(II), which enables access to Ni(III) in the absence of external oxidants or photoredox catalysts. As such, it is possible to facilitate Ni-catalyzed C-O bond formation solely by visible light irradiation, thus representing an alternative strategy for catalyst activation in Ni cross-coupling reactions.
- Shields, Benjamin J.,Kudisch, Bryan,Scholes, Gregory D.,Doyle, Abigail G.
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- Enabling Metallophotoredox Catalysis in Parallel Solution-Phase Synthesis Using Disintegrating Reagent Tablets
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Compressed tablets containing a mixture of a photocatalyst, a nickel catalyst, an inorganic base, and an inert excipient are employed as a fast, safe, and user-friendly chemical delivery system for two different metallophotoredox-catalyzed reactions. This delivery method simplifies the preparation of compound libraries using photoredox chemistry in a parallel setting. The reagent tablets were successfully applied to late-stage functionalization of drug-like intermediates. These tablets can be prepared with various reagents and catalysts in different sizes and be stored on the bench thanks to blister packaging.
- Borlinghaus, Niginia,Sch?nfeld, Barbara,Heitz, Stephanie,Klee, Johanna,Vukeli?, Stella,Braje, Wilfried M.,Jolit, Anais
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p. 16535 - 16547
(2021/12/02)
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- Photoredox Nickel-Catalyzed C-S Cross-Coupling: Mechanism, Kinetics, and Generalization
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Photoredox-mediated nickel-catalyzed cross-couplings have evolved as a new effective strategy to forge carbon-heteroatom bonds that are difficult to access with traditional methods. Experimental mechanistic studies are challenging because these reactions involve multiple highly reactive intermediates and perplexing reaction pathways, engendering competing, but unverified, proposals for substrate conversions. Here, we report a comprehensive mechanistic study of photoredox nickel-catalyzed C-S cross-coupling based on time-resolved transient absorption spectroscopy, Stern-Volmer quenching, and quantum yield measurements. We have (i) discovered a self-sustained productive Ni(I/III) cycle leading to a quantum yield φ > 1; (ii) found that pyridinium iodide, formed in situ, serves as the dominant quencher for the excited state photocatalyst and a critical redox mediator to facilitate the formation of the active Ni(I) catalyst; and (iii) observed critical intermediates and determined the rate constants associated with their reactivity. Not only do the findings reveal a complete reaction cycle for C-S cross-coupling, but the mechanistic insights have also allowed for the reaction efficiency to be optimized and the substrate scope to be expanded from aryl iodides to include aryl bromides, thus broadening the applicability of photoredox C-S cross-coupling chemistry.
- Qin, Yangzhong,Sun, Rui,Gianoulis, Nikolas P.,Nocera, Daniel G.
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supporting information
p. 2005 - 2015
(2021/02/06)
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- Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2)–C(sp3)Coupling Reactions
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A number of new transition metal catalyzed methods for the formation of C(sp2)–C(sp3) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2)–C(sp3) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2)–C(sp3) coupling through stoichiometric studies and also explore their catalytic activity.
- Mohadjer Beromi, Megan,Brudvig, Gary W.,Hazari, Nilay,Lant, Hannah M. C.,Mercado, Brandon Q.
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supporting information
p. 6094 - 6098
(2019/04/03)
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- Ni-Catalyzed β-Alkylation of Cyclopropanol-Derived Homoenolates
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Metal homoenolates are valuable synthetic intermediates which provide access to β-functionalized ketones. In this report, we disclose a Ni-catalyzed β-alkylation reaction of cyclopropanol-derived homoenolates using redox-active N-hydroxyphthalimide (NHPI) esters as the alkylating reagents. The reaction is compatible with 1°, 2°, and 3° NHPI esters. Mechanistic studies imply radical activation of the NHPI ester and 2e β-carbon elimination occurring on the cyclopropanol.
- Mills, L. Reginald,Zhou, Cuihan,Fung, Emily,Rousseaux, Sophie A. L.
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supporting information
p. 8805 - 8809
(2019/11/03)
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- Elucidation of a Redox-Mediated Reaction Cycle for Nickel-Catalyzed Cross Coupling
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A reaction cycle for redox-mediated, Ni-catalyzed aryl etherification is proposed under both photoredox and electrochemically mediated conditions. We demonstrate that a self-sustained Ni(I/III) cycle is operative in both cases by chemically synthesizing a
- Sun, Rui,Qin, Yangzhong,Ruccolo, Serge,Schnedermann, Christoph,Costentin, Cyrille,Nocera, Daniel G.
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supporting information
p. 89 - 93
(2019/01/16)
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- A fluorine-containing methyl compounds and its preparation method (by machine translation)
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The invention discloses a fluorine-containing methyl compounds and its preparation method. The invention provides a fluorine-containing shown as formula C methyl compounds, wherein R is aryl group containing, or, containing a hetero aryl group, and the aryl group or the heteroaryl on the aromatic carbon atom and CFm Hn Connected, m is 1 or 2, m + n=3. The compounds according to the prior art is difficult to make, the preparation method of the raw material and the catalyst are the ordinary industrial raw materials, cheap and easy to obtain, high reaction efficiency, high yield, after treatment is simple, low toxicity, environmental protection, functional group compatibility is good, broad-spectrum is strong, the production cost is low, it has very good market application prospect. (by machine translation)
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Paragraph 0173; 01774; 0175
(2019/05/11)
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- Silyl Radical Activation of Alkyl Halides in Metallaphotoredox Catalysis: A Unique Pathway for Cross-Electrophile Coupling
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A strategy for cross-electrophile coupling has been developed via the merger of photoredox and transition metal catalysis. In this report, we demonstrate the use of commercially available tris(trimethylsilyl)silane with metallaphotoredox catalysis to efficiently couple alkyl bromides with aryl or heteroaryl bromides in excellent yields. We hypothesize that a photocatalytically generated silyl radical species can perform halogen-atom abstraction to activate alkyl halides as nucleophilic cross-coupling partners. This protocol allows the use of mild yet robust conditions to construct Csp3-Csp2 bonds generically via a unique cross-coupling pathway.
- Zhang, Patricia,Le, Chi Chip,MacMillan, David W. C.
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supporting information
p. 8084 - 8087
(2016/07/16)
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- Nickel-Catalyzed Difluoroalkylation of (Hetero)Arylborons with Unactivated 1-Bromo-1,1-difluoroalkanes
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A nickel-catalyzed cross-coupling between (hetero)arylborons and unactivated 1-bromo-1,1-difluoroalkanes has been developed. The use of two ligands (a bidentate bipyridine-based ligand, 4,4′-ditBu-bpy, and a monodentate pyridine-based ligand, DMAP) offers a highly efficient nickel-based catalytic system to prepare difluoroalkylated arenes which have important applications in medicinal chemistry. Ligand combo: The title reaction requires the use of a combined (2+1) ligand system, that is, a combination of a bi- and monodentate ligand (4,4′-ditBu-bpy + DMAP). This system allows employment of a wide range of unactivated 1-bromo-1,1-difluoroalkanes as coupling partners, thus providing a highly efficient method for applications in drug discovery and development. bpy=bipyridine, DMAP=4-(N,N-dimethylamino)pyridine.
- Xiao, Yu-Lan,Min, Qiao-Qiao,Xu, Chang,Wang, Ruo-Wen,Zhang, Xingang
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supporting information
p. 5837 - 5841
(2016/05/09)
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- Diimine supported group 10 hydroxo, oxo, amido, and imido complexes
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A series of L2 = diimine (Bian = bis(3,5-diisopropylphenylimino) acenapthene, But2bpy = 4,4′-di-tert-butyl-2, 2′-bipyridine) supported aqua, hydroxo, oxo, amido, imido, and mixed complexes have been prepared. Deprotonation of [L2Pt(μ-OH)] 22+ with 1,8-bis(dimethylamino)naphthalene, NaH, or KOH yields [(L2Pt)2(μ-OH)(μ-O)]+ as purple (Bian) or red (But2bpy) solids. Excess KOH gives dark blue [(Bian)Pt(μ-O)]2. MeOTf addition to [(But 2bpy)2Pt2(μ-OH)(μ-O)]+ gives [(But2bpy)2Pt2(μ-OH)(μ-OMe)] 2+ while [(Bian)Pt(μ-O)]2 yields [(Bian) 2Pt2(μ-OMe)(μ-O)]+. Treatment of [(Bian)Pt(μ-O)]2 with "(Ph3P)Au+" gives deep purple [(Bian)2Pt2(μ-O)(μ-OAuPPh 3)]+ while (COD)Pt(OTf)2 gives a low yield of [(Bian)Pt3(μ-OH)3(COD)2](OTf)3. Ni(But2bpy)Cl2 and [(Ph3PAu) 3(μ-O)]+ in a 3: 2 ratio yield red [Ni 3(But2bpy)3(μ-O) 2]2+. M(But2bpy)Cl2 (M = Pd, Pt) and [(Ph3PAu)3(μ-O)]+ give [M(But2bpy)(μ-OAuPPh3)]2 2+ and [Pd4(But2bpy) 4(μ-OAuPPh3)]3+. Addition of ArNH 2 to [M(But2bpy)(μ-OH)]2 2+ (M = Pd, Pt) gives [Pt2(But 2bpy)2(μ-NHAr)(μ-OH)]2+ (Ar = Ph, 4-tol, 4-C6H4NO2) and [M(But 2bpy)(μ-NHAr)]22+ (Ar = Ph, tol). Deprotonation of [Pt2(But2bpy) 2(μ-NH-tol)(μ-OH)]2+ with 1,8-bis(dimethylamino) naphthalene or NaH gives [Pt2(But2bpy) 2(μ-NH-tol)(μ-O)]+. Deprotonation of [Pt(Bu t2bpy)(μ-NH-tol)]22+ with KOBut gives deep green [Pt(But2bpy)(μ-N-tol) ]2. The triflate complexes M(But2bpy)(OTf) 2 (M = Pd, Pt) are obtained from M(But2bpy) Cl2 and AgOTf. Treatment of Pt(But2bpy)(OTf) 2 with water gives the aqua complex [Pt(But 2bpy)(H2O)2](OTf)2. This journal is The Royal Society of Chemistry.
- Singh, Anupam,Anandhi,Cinellu, Maria Agostina,Sharp, Paul R.
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p. 2314 - 2327
(2008/09/19)
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