Convenient C(sp³)–H bond functionalisation of light alkanes and other compounds by iron photocatalysis

Green Chemistry, Год журнала: 2021, Номер 23(18), С. 6984 - 6989

Опубликована: Янв. 1, 2021

A practical and green iron-catalyzed photoredox system for C–H functionalization of ethane, propane, other light alkanes was developed.

Язык: Английский

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Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp³)–H Alkylation

ACS Catalysis, Год журнала: 2021, Номер 11(12), С. 7442 - 7449

Опубликована: Июнь 8, 2021

Herein we disclose an iron-catalyzed method to access skeletal rearrangement reactions akin the Dowd-Beckwith ring expansion from unactivated C(sp3)-H bonds. Photoinduced ligand-to-metal charge transfer at iron center generates a chlorine radical, which abstracts electron-rich The resulting unstable alkyl radicals can undergo in presence of suitable functionality. Addition electron deficient olefin, recombination with photoreduced complex, and subsequent protodemetallation allows for redox-neutral alkylation radical. Simple adjustments reaction conditions enable selective synthesis directly alkylated or rearranged-alkylated products. As radical clock, these rearrangements also measurement rate constants addition into various olefins Giese reaction.

Язык: Английский

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A cross-dehydrogenative C(sp3)−H heteroarylation via photo-induced catalytic chlorine radical generation

Nature Communications, Год журнала: 2021, Номер 12(1)

Опубликована: Июнь 29, 2021

Abstract Hydrogen atom abstraction (HAT) from C( sp 3 )–H bonds of naturally abundant alkanes for alkyl radical generation represents a promising yet underexplored strategy in the alkylation reaction designs since involving stoichiometric oxidants, excessive alkane loading, and limited scope are common drawbacks. Here we report photo-induced chemical oxidant-free cross-dehydrogenative coupling (CDC) between heteroarenes using catalytic chloride cobalt catalyst. Couplings strong bond-containing substrates complex heteroarenes, have been achieved with satisfactory yields. This dual platform features situ engendered chlorine exploits cobaloxime catalyst to enable hydrogen evolution turnover. The practical value this protocol was demonstrated by gram-scale synthesis alkylated heteroarene merely equiv. loading.

Язык: Английский

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Iron-Catalyzed C(Sp³)–H Borylation, Thiolation, and Sulfinylation Enabled by Photoinduced Ligand-to-Metal Charge Transfer

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(13), С. 7600 - 7611

Опубликована: Март 23, 2023

Catalytic C(sp3)-H functionalization has provided enormous opportunities to construct organic molecules, facilitating the derivatization of complex pharmaceutical compounds. Within this framework, direct hydrogen atom transfer (HAT) photocatalysis becomes an appealing approach goal. However, viable substrates utilized in these protocols are limited, and site selectivity shows preference activated thermodynamically favored bonds. Herein, we describe development undirected iron-catalyzed borylation, thiolation, sulfinylation reactions enabled by photoinduced ligand-to-metal charge (LMCT) process. These exhibit remarkably broad substrate scope (>150 examples total), most importantly, all three show unconventional regioselectivity, with occurrence preferentially at distal methyl position. The procedures operationally simple readily scalable provide access high-value products from hydrocarbons one step. Mechanistic studies control experiments indicate that afforded is not only relevant HAT species but also largely affected use boron- sulfone-based radical acceptors.

Язык: Английский

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A Unified Approach to Decarboxylative Halogenation of (Hetero)aryl Carboxylic Acids

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(18), С. 8296 - 8305

Опубликована: Апрель 29, 2022

Aryl halides are a fundamental motif in synthetic chemistry, playing critical role metal-mediated cross-coupling reactions and serving as important scaffolds drug discovery. Although thermal decarboxylative functionalization of aryl carboxylic acids has been extensively explored, the scope existing halodecarboxylation methods remains limited, there currently exists no unified strategy that provides access to any type halide from an acid precursor. Herein, we report general catalytic method for direct halogenation (hetero)aryl via ligand-to-metal charge transfer. This accommodates exceptionally broad substrates. We leverage radical intermediate toward divergent pathways: (1) atom transfer bromo- or iodo(hetero)arenes (2) capture by copper subsequent reductive elimination generate chloro- fluoro(hetero)arenes. The proposed mechanism is supported through array spectroscopic studies.

Язык: Английский

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Elucidating the Mechanism of Excited-State Bond Homolysis in Nickel–Bipyridine Photoredox Catalysts

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(14), С. 6516 - 6531

Опубликована: Март 30, 2022

Ni 2,2'-bipyridine (bpy) complexes are commonly employed photoredox catalysts of bond-forming reactions in organic chemistry. However, the mechanisms by which they operate still under investigation. One potential mode catalysis is via entry into Ni(I)/Ni(III) cycles, can be made possible light-induced, excited-state Ni(II)-C bond homolysis. Here, we report experimental and computational analyses a library Ni(II)-bpy aryl halide complexes, Ni(Rbpy)(R'Ph)Cl (R = MeO, t-Bu, H, MeOOC; R' CH3, OMe, F, CF3), to illuminate mechanism At given excitation wavelengths, photochemical homolysis rate constants span 2 orders magnitude across these structures correlate linearly with Hammett parameters both bpy ligands, reflecting structural control over key metal-to-ligand charge-transfer (MLCT) ligand-to-metal (LMCT) energy surfaces (PESs). Temperature- wavelength-dependent investigations reveal moderate barriers (ΔH‡ ∼ 4 kcal mol-1) minimum threshold (∼55 mol-1, 525 nm), respectively. Correlations electronic structure calculations further support repulsive triplet PESs featuring critical aryl-to-Ni LMCT lead rupture. Structural provides rational approach utilize photonic leverage processes synthetic

Язык: Английский

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Modular Access to Chiral α-(Hetero)aryl Amines via Ni/Photoredox-Catalyzed Enantioselective Cross-Coupling

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(19), С. 8797 - 8806

Опубликована: Май 3, 2022

Chiral α-aryl N-heterocycles are commonly found in natural products, pharmaceutical agents, and chiral catalysts but remain challenging to access via asymmetric catalysis. Herein, we report a general modular approach for the direct enantioselective α-arylation of saturated azacycles acyclic N-alkyl benzamides nickel/photoredox dual This process exploits hydrogen atom transfer ability photoeliminated chlorine radicals convert corresponding α-amino alkyl that then coupled with ubiquitous inexpensive (hetero)aryl chlorides. These coupling reactions require no oxidants or organometallic reagents, feature feedstock starting materials, broad substrate scope, high enantioselectivities, applicable late-stage diversification medicinally relevant complex molecules. Mechanistic studies suggest nickel catalyst uncommonly plays multiple roles, accomplishing radical generation, capture, cross-coupling, induction.

Язык: Английский

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Taming the Chlorine Radical: Enforcing Steric Control over Chlorine-Radical-Mediated C–H Activation

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(3), С. 1464 - 1472

Опубликована: Янв. 12, 2022

Chlorine radicals readily activate C-H bonds, but the high reactivity of these intermediates precludes their use in regioselective functionalization reactions. We demonstrate that secondary coordination sphere a metal complex can confine photoeliminated chlorine and afford steric control over reactivity. Specifically, series iron(III) chloride pyridinediimine complexes exhibit activity for photochemical C(sp3)-H chlorination bromination with selectivity primary overriding thermodynamic preference weaker tertiary bonds. Transient absorption spectroscopy reveals Cl· remains confined through formation Cl·|arene aromatic groups on ligand. Furthermore, photocrystallography confirms this arises from generation within environment defined by iron sphere.

Язык: Английский

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A practical FeCl3/HCl photocatalyst for versatile aliphatic C–H functionalization

Chem Catalysis, Год журнала: 2022, Номер 2(5), С. 1211 - 1222

Опубликована: Апрель 20, 2022

Язык: Английский

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Decarboxylative Borylation and Cross-Coupling of (Hetero)aryl Acids Enabled by Copper Charge Transfer Catalysis

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(14), С. 6163 - 6172

Опубликована: Апрель 4, 2022

We report a copper-catalyzed strategy for arylboronic ester synthesis that exploits photoinduced ligand-to-metal charge transfer (LMCT) to convert (hetero)aryl acids into aryl radicals amenable ambient-temperature borylation. This near-UV process occurs under mild conditions, requires no prefunctionalization of the native acid, and operates broadly across diverse aryl, heteroaryl, pharmaceutical substrates. also one-pot procedure decarboxylative cross-coupling merges catalytic LMCT borylation palladium-catalyzed Suzuki-Miyaura arylation, vinylation, or alkylation with organobromides access range value-added products. The utility these protocols is highlighted through development heteroselective double-decarboxylative C(sp2)-C(sp2) coupling sequence, pairing halogenation processes two distinct (including substrates) subsequent cross-coupling.

Язык: Английский

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