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

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(18), P. 8296 - 8305

Published: April 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.

Language: 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, Journal Year: 2022, Volume and Issue: 144(14), P. 6163 - 6172

Published: April 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.

Language: Английский

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Red Light-Based Dual Photoredox Strategy Resembling the Z-Scheme of Natural Photosynthesis

JACS Au, Journal Year: 2022, Volume and Issue: 2(6), P. 1488 - 1503

Published: June 10, 2022

Photoredox catalysis typically relies on the use of single chromophores, whereas strategies, in which two different light absorbers are combined, rare. In photosystems I and II green plants, separate chromophores P680 P700 both absorb independently one another, then their excitation energy is combined so-called Z-scheme, to drive an overall reaction that thermodynamically very demanding. Here, we adapt this concept perform photoredox reactions organic substrates with input red photons instead blue or UV light. Specifically, a CuI bis(α-diimine) complex combination situ formed 9,10-dicyanoanthracenyl radical anion presence excess diisopropylethylamine catalyzes ca. 50 dehalogenation detosylation reactions. This dual approach seems useful because less damaging has greater penetration depth than radiation. UV-vis transient absorption spectroscopy reveals subtle change solvent from acetonitrile acetone induces changeover mechanism, involving either dominant photoinduced electron transfer triplet-triplet pathway. Our study illustrates mechanistic complexity systems operating under multiphotonic conditions, it provides insights into how competition between desirable unwanted steps can become more controllable.

Language: Английский

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Photocatalytic hydrofluoroalkylation of alkenes with carboxylic acids

Nature Chemistry, Journal Year: 2023, Volume and Issue: 15(12), P. 1683 - 1692

Published: Nov. 13, 2023

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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Merging Photoinduced Iron-Catalyzed Decarboxylation with Copper Catalysis for C–N and C–C Couplings

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(3), P. 1678 - 1685

Published: Jan. 13, 2023

We report a photoinduced iron/copper dual-catalytic strategy for the radical decarboxylation functionalization of aliphatic carboxylic acids. The ligand-to-iron charge transfer process under light was initially occurred to generate an unstabilized alkyl radical, and copper catalyst delivered enabled subsequent coupling reactions form C–N or C–C bonds. By merging iron-catalyzed with catalysis, this system allows smooth conversion wide range acids amination, decarboxylative dehydrogenation, alkylation efficiently. A variety complex drug natural molecules is applicable, suggesting that would facilitate rapid compound library synthesis benefit discovery pharmaceutical agents.

Language: Английский

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Synthetic Application of Bismuth LMCT Photocatalysis in Radical Coupling Reactions

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(2), P. 1125 - 1132

Published: Jan. 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.

Language: Английский

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