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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Iron Photoredox Catalysis–Past, Present, and Future

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(17), С. 9369 - 9388

Опубликована: Апрель 20, 2023

Photoredox catalysis of organic reactions driven by iron has attracted substantial attention throughout recent years, due to potential environmental and economic benefits. In this Perspective, three major strategies were identified that have been employed date achieve reactivities comparable the successful noble metal photoredox catalysis: (1) Direct replacement a center in archetypal polypyridyl complexes, resulting metal-centered photofunctional state. (2) situ generation photoactive complexes substrate coordination where are via intramolecular electron transfer involving charge-transfer states, for example, through visible-light-induced homolysis. (3) Improving excited-state lifetimes redox potentials states new ligand design. We seek give an overview evaluation developments rapidly growing field and, at same time, provide outlook on future iron-based catalysis.

Язык: Английский

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Photoactive Metal-to-Ligand Charge Transfer Excited States in 3d⁶ Complexes with Cr⁰, Mn^I, Fe^II, and Co^III

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(9), С. 4903 - 4920

Опубликована: Фев. 21, 2023

Many coordination complexes and organometallic compounds with the 4d6 5d6 valence electron configurations have outstanding photophysical photochemical properties, which stem from metal-to-ligand charge transfer (MLCT) excited states. This substance class makes extensive use of most precious least abundant metal elements, consequently there has been a long-standing interest in first-row transition photoactive MLCT Semiprecious copper(I) its completely filled 3d subshell is relatively straightforward well explored case, but 3d6 partially d-orbitals lead to energetically low-lying metal-centered (MC) states that can cause undesirably fast state deactivation. Herein, we discuss recent advances made isoelectronic Cr0, MnI, FeII, CoIII compounds, for long-lived become accessible over past five years. Furthermore, possible future developments search new subshells next-generation applications photophysics photochemistry.

Язык: Английский

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Photocatalytic hydrofluoroalkylation of alkenes with carboxylic acids

Nature Chemistry, Год журнала: 2023, Номер 15(12), С. 1683 - 1692

Опубликована: Ноя. 13, 2023

Язык: Английский

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Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C–H Functionalization

Journal of the American Chemical Society, Год журнала: 2022, Номер 145(1), С. 359 - 376

Опубликована: Дек. 20, 2022

The intermediacy of alkoxy radicals in cerium-catalyzed C–H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)–alkoxide complexes have synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified as the sole heteroatom-centered radical species generated ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom (HAT) verified kinetic analysis, density functional theory (DFT) calculations, reactions under strictly chloride-free conditions. These experimental findings establish critical role Ce-LMCT catalysis definitively preclude involvement chlorine radical. This study also reinforced necessity a high relative ratio alcohol vs Ce for selective alkoxy-radical-mediated HAT, seemingly trivial changes can lead to drastically different mechanistic pathways. Importantly, previously proposed radical–alcohol complex, postulated explain alkoxy-radical-enabled selectivities this system, examined scrutiny ruled out regioselectivity studies, experiments, high-level calculations. Moreover, peculiar selectivity generation LMCT homolysis heteroleptic analyzed back-electron (BET) may regulated efficiency formation ligand-centered radicals.

Язык: Английский

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Resurgence and advancement of photochemical hydrogen atom transfer processes in selective alkane functionalizations

Chemical Science, Год журнала: 2023, Номер 14(25), С. 6841 - 6859

Опубликована: Янв. 1, 2023

The selective functionalization of alkanes has long been recognized as a prominent challenge and an arduous task in organic synthesis. Hydrogen atom transfer (HAT) processes enable the direct generation reactive alkyl radicals from feedstock have successfully employed industrial applications such methane chlorination process,

Язык: Английский

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Multiplicative enhancement of stereoenrichment by a single catalyst for deracemization of alcohols

Science, Год журнала: 2023, Номер 382(6669), С. 458 - 464

Опубликована: Окт. 26, 2023

Stereochemical enrichment of a racemic mixture by deracemization must overcome unfavorable entropic effects as well the principle microscopic reversibility; recently, photochemical reaction pathways unveiled energetic input light have led to innovations toward this end, most often ablation stereogenic C(sp3)-H bond. We report photochemically driven protocol in which single chiral catalyst two mechanistically different steps, C-C bond cleavage and formation, achieve multiplicative enhancement stereoinduction, leads high levels stereoselectivity. Ligand-to-metal charge transfer excitation titanium coordinated phosphoric acid or bisoxazoline efficiently enriches alcohols that feature adjacent fully substituted centers enantiomeric ratios up 99:1. Mechanistic investigations support pathway sequential radical-mediated scission formation through common prochiral intermediate reveal that, although overall stereoenrichment is high, selectivity each individual step moderate.

Язык: Английский

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Synthetic Application of Bismuth LMCT Photocatalysis in Radical Coupling Reactions

ACS Catalysis, Год журнала: 2023, Номер 13(2), С. 1125 - 1132

Опубликована: Янв. 9, 2023

Ligand-to-metal charge transfer (LMCT) photocatalysis allows the activation and synthetic utilization of halides other heteroatoms in metal complexes. Many metals are known to undergo LMCT but so far remain underutilized field catalysis. A screening assay identifying activity helped us expand this catalysis concept application bismuth organic radical coupling reactions. We demonstrate its for generation two different radicals (chlorine carboxyl) net-oxidative as well redox-neutral photochemical Detailed investigation model Giese-type revealed BiCl4– BiCl52– catalytically active species under 385 nm irradiation. Combined cyclic voltammetry UV–vis studies gave insight into reactivity highly reactive bismuth(II) catalyst fragment.

Язык: Английский

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Iron-mediated modular decarboxylative cross-nucleophile coupling

Chem, Год журнала: 2023, Номер 9(6), С. 1610 - 1621

Опубликована: Май 4, 2023

Язык: Английский

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Direct Decarboxylation of Trifluoroacetates Enabled by Iron Photocatalysis**

Angewandte Chemie International Edition, Год журнала: 2023, Номер 63(5)

Опубликована: Дек. 13, 2023

Trifluoroacetates are the most abundant and accessible sources of trifluoromethyl groups, which key components in pharmaceuticals agrochemicals. The generation reactive radicals from trifluoroacetates requires their decarboxylation, is hampered by high oxidation potential. This constitutes a major challenge for redox-based methods, because need to pair redox potentials with trifluoroacetate. Here we report strategy based on iron photocatalysis promote direct photodecarboxylation that displays reactivity features escape limitations. Our synthetic design has enabled use trifluoromethylation more easily oxidizable organic substrates, offering new opportunities late-stage derivatization campaigns using chemical feedstocks, Earth-abundant catalysts, visible-light.

Язык: Английский

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