Ligand‐to‐Metal Charge Transfer (LMCT) Photochemistry at 3d‐Metal Complexes: An Emerging Tool for Sustainable Organic Synthesis

ChemCatChem, Journal Year: 2022, Volume and Issue: 14(19)

Published: Aug. 11, 2022

Abstract Despite the rich photochemistry of 3d‐metal complexes, utilization excited‐state reactivity these compounds in organic synthesis has been historically overlooked. The advent photoredox catalysis changed perception synthetic chemists towards photochemistry, and nowadays potential photoinduced, outer‐sphere single‐electron transfer events is widely recognized. More recently, an emerging new mode photoactivation taken spotlight, based on inner‐sphere triggered by population ligand‐to‐metal charge‐transfer (LMCT) excited states. Contrarily to photoredox, LMCT‐activation does not rely matching redox potentials, offers unique profiles particularly well suited Earth‐abundant metal complexes. Those appealing features are propelling development methods using this blueprint generate highly reactive open‐shell species under mild conditions. aim contribution provide a didactical tool for comprehension concept facilitate methodologies achieve sustainable chemical transformations.

Language: Английский

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Photoactive Copper Complexes: Properties and Applications

Chemical Reviews, Journal Year: 2022, Volume and Issue: 122(22), P. 16365 - 16609

Published: Nov. 9, 2022

Photocatalyzed and photosensitized chemical processes have seen growing interest recently become among the most active areas of research, notably due to their applications in fields such as medicine, synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported date, photoactive copper(I) complexes been shown be especially attractive, not only alternative noble metal complexes, extensively studied utilized recently. They are at core this review article which is divided into two main sections. The first one focuses on an exhaustive comprehensive overview structural, photophysical electrochemical properties mononuclear typical examples highlighting critical structural parameters impact being presented enlighten future design complexes. second section devoted application (photoredox catalysis organic reactions polymerization, hydrogen production, photoreduction carbon dioxide dye-sensitized solar cells), illustrating progression from early current state-of-the-art showcasing how some limitations can overcome with high versatility.

Language: Английский

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Carboxylic Acids as Adaptive Functional Groups in Metallaphotoredox Catalysis

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 55(23), P. 3481 - 3494

Published: Nov. 22, 2022

The development of palladium-catalyzed cross-coupling methods for the activation C(sp2)-Br bonds facilitated access to arene-rich molecules, enabling a concomitant increase in prevalence this structural motif drug molecules recent decades. Today, there is growing appreciation value incorporating saturated C(sp3)-rich scaffolds into pharmaceutically active as means achieve improved solubility and physiological stability, providing impetus develop new coupling strategies these challenging motifs most straightforward way possible. As an alternative classical two-electron chemistry, redox chemistry can enable elusive transformations, recently, by interfacing abundant first-row transition-metal catalysis with photoredox catalysis. such, functionalization ubiquitous versatile functional handles such (aliphatic) carboxylic acids via metallaphotoredox has emerged valuable field research over past eight years.In Account, we will outline progress methodologies that employ aliphatic (hetero)aromatic adaptive groups. Whereas decarboxylative often necessitate preactivated form redox-active esters or ligands hypervalent iodine reagents, direct use native acid functionality are highly desired have been accomplished through protocols. found bench-stable undergo diverse alkylation, arylation, amination, trifluoromethylation, leveraging prevalent transition metals nickel copper. Likewise, aryl now able halogenation borylation, entry points traditional, primarily palladium- copper-catalyzed strategies. Given breadth group tolerance employed reaction conditions, late-stage toward targets become standard tool design, synthesis various diversified molecules. rapid rise positively inspired pharmaceutical discovery be further accelerated novel development. achievement generality optimization campaigns allows future breakthroughs render protocols more reliable applicable industry. This article intended highlight, particular, (i) employment (hetero)aryl powerful (ii) need still-elusive selective transformations.We strongly believe functionalities inspire researchers across world investigate complex molecular targets.

Language: 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, Journal Year: 2023, Volume and Issue: 145(13), P. 7600 - 7611

Published: March 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.

Language: 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, Journal Year: 2022, Volume and Issue: 145(1), P. 359 - 376

Published: Dec. 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.

Language: Английский

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Metal-Free Amino(hetero)arylation and Aminosulfonylation of Alkenes Enabled by Photoinduced Energy Transfer

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(30), P. 16630 - 16641

Published: July 24, 2023

β-(Hetero)arylethylamines are privileged structural motifs found in many high-value organic molecules, including pharmaceuticals and natural products. To construct these important molecular skeletons, previous methods mainly achieved by amino(hetero)arylation reaction with the aid of transition metals preactivated substrates. Herein, we report a metal-free photoinduced intermolecular for single-step installation both (hetero)aryl iminyl groups across alkenes an efficient regioselective manner. This method shows broad scope (up to 124 examples) excellent tolerance various olefins─from simplest ethylene complex multisubstituted can all participate reaction. Furthermore, aminosulfonylation be also conducted presence sodium bisulfite as SO2 source.

Language: Английский

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Free Carboxylic Acids: The Trend of Radical Decarboxylative Functionalization

European Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 26(21)

Published: April 7, 2023

Abstract The exceptional versatility of carboxylic acids has been extensively exploited in organic synthesis across several decades. There a recent upsurge radical decarboxylative transformations. process can be initiated under mild conditions, and the resultant radicals have orthogonal reactivities to closed‐shell species, thus providing immense opportunities for streamlining novel reactions. use free is most desirable owing its high atom step economy. Aiming demonstrate attractiveness strategy inspire chemists tackle existing challenges, this review outlines advances on functionalization acids.

Language: Английский

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Iron-mediated modular decarboxylative cross-nucleophile coupling

Chem, Journal Year: 2023, Volume and Issue: 9(6), P. 1610 - 1621

Published: May 4, 2023

Language: Английский

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Direct Decarboxylation of Trifluoroacetates Enabled by Iron Photocatalysis**

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 63(5)

Published: Dec. 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.

Language: Английский

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Catalysis in the Excited State: Bringing Innate Transition Metal Photochemistry into Play

ACS Catalysis, Journal Year: 2025, Volume and Issue: unknown, P. 4665 - 4680

Published: March 5, 2025

Transition metal catalysis is an indispensable tool for organic synthesis that has been harnessed, modulated, and perfected many decades by careful selection of centers ligands, giving rise to synthetic methods with unparalleled efficiency chemoselectivity. Recent developments have demonstrated how light irradiation can also be recruited as a powerful dramatically alter the outcome catalytic reactions, providing access innovative pathways remarkable potential. In this context, adoption photochemical conditions mainstream strategy drive reactions unveiled exciting opportunities exploit rich excited-state framework transition metals applications. This Perspective examines advances in application complexes standalone photocatalysts, exploiting innate reactivity their excited states beyond common use photoredox catalysts. An account relevant examples dissected provide discussion on electronic reorganization, orbitals involved, associated different types states. analysis aims practitioners fundamental principles guiding strategies understand, design, apply light-activation homogeneous synthesis.

Language: Английский

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