Visible‐Light Photocatalysis: Does It Make a Difference in Organic Synthesis?

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(32), P. 10034 - 10072

Published: Feb. 21, 2018

Visible-light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. Photocatalytic variants have been reported for many important transformations, such as cross-coupling reactions, α-amino functionalizations, cycloadditions, ATRA or fluorinations. To help chemists select photocatalytic methods their synthesis, we compare this Review classical and procedures selected classes of reactions highlight advantages limitations. In cases, proceed under milder reaction conditions, typically at room temperature, stoichiometric reagents are replaced by simple oxidants reductants, air, oxygen, amines. Does visible-light make difference synthesis? The prospect shuttling electrons back forth to substrates intermediates selectively transfer energy through visible-light-absorbing photocatalyst holds promise improve current radical chemistry open up new avenues accessing reactive species hitherto unknown, especially merging with organo- metal catalysis.

Language: Английский

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Photoredox Catalysis for Building C–C Bonds from C(sp²)–H Bonds

Chemical Reviews, Journal Year: 2018, Volume and Issue: 118(16), P. 7532 - 7585

Published: July 16, 2018

Transition metal-catalyzed C–H bond functionalizations have been the focus of intensive research over last decades for formation C–C bonds from unfunctionalized arenes, heteroarenes, alkenes. These direct transformations provide new approaches in synthesis with high atom- and step-economy compared to traditional catalytic cross-coupling reactions. However, such methods still suffer several limitations including functional group tolerance lack regioselectivity. In addition, they often require harsh reaction conditions some them need use strong oxidant, a stoichiometric amount, avoiding these processes be truly eco-friendly. The photoredox catalysis has contributed significant expansion scope C(sp2)–H which include arylations, (perfluoro)alkylations, acylations, even cyanations. Most involve photochemical induced generation radical followed by its regioselective addition or alkenes, leading building C(sp2)–C bond. plays crucial roles reactions promoting electron transfer, enabling species single either oxidation reduction. Such operating at room temperature allow chemo-, regio-, stereoselectivity. This review surveys initiated involves functionalization step, describes advantages functionalizations, presents mechanistic insights into role played catalysts.

Language: Английский

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Electrocatalytic C–H Activation

ACS Catalysis, Journal Year: 2018, Volume and Issue: 8(8), P. 7086 - 7103

Published: June 18, 2018

C–H activation has emerged as a transformative tool in molecular synthesis, but until recently oxidative activations have largely involved the use of stoichiometric amounts expensive and toxic metal oxidants, compromising overall sustainable nature chemistry. In sharp contrast, electrochemical been identified more efficient strategy that exploits storable electricity place byproduct-generating chemical reagents. Thus, transition-metal catalysts were shown to enable versatile reactions manner. While palladium catalysis set stage for C(sp2)–H C(sp3)–H functionalizations by N-containing directing groups, rhodium ruthenium allowed weakly coordinating amides acids. contrast these precious 4d transition metals, recent year witnessed emergence cobalt oxygenations, nitrogenations, C–C-forming [4+2] alkyne annulations. Thereby, silver(I) oxidants was prevented, improving environmentally benign catalysis. Herein, we summarize major advances organometallic otherwise inert bonds electrocatalysis through May 2018.

Language: Английский

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Photoredox-Mediated Routes to Radicals: The Value of Catalytic Radical Generation in Synthetic Methods Development

ACS Catalysis, Journal Year: 2017, Volume and Issue: 7(4), P. 2563 - 2575

Published: March 14, 2017

Photoredox catalysis has experienced a revitalized interest from the synthesis community during past decade. For example, photoredox/Ni dual protocols have been developed to overcome several inherent limitations of palladium-catalyzed cross-couplings by invoking single-electron transmetalation pathway. This Perspective highlights advances made our laboratory since inception cross-coupling benzyltrifluoroborates with aryl bromides. In addition broadening scope trifluoroborate coupling partners, research using readily oxidized hypervalent silicates as radical precursors that demonstrate functional group compatibility is highlighted. The pursuit electrophilic partners beyond (hetero)aryl bromides also led incorporation new classes C(sp2)-hybridized substrates into light-mediated cross-coupling. Advances expand toolbox utilizing feedstock chemicals (e.g., aldehydes) access radicals were previously inaccessible trifluoroborates and are emphasized. Additionally, organic photocatalysts investigated replacements for their expensive iridium- ruthenium-based counterparts. Lastly, net C–H functionalization partner in an effort improve atom economy presented. An underlying theme all these studies value generating catalytic manner, rather than stoichiometrically.

Language: Английский

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Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2752 - 2906

Published: Aug. 10, 2021

Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing plethora opportunities to synthetic organic chemists. However, performing photochemical transformation can be quite challenge because various issues related the delivery photons. These challenges barred widespread adoption steps industry. past decade, several technological innovations led more reproducible, selective, and scalable photoinduced reactions. Herein, we provide comprehensive overview these exciting advances, including flow chemistry, high-throughput experimentation, reactor design scale-up, combination photo- electro-chemistry.

Language: Английский

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Metalla-electrocatalyzed C–H Activation by Earth-Abundant 3d Metals and Beyond

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 53(1), P. 84 - 104

Published: Dec. 19, 2019

To improve the efficacy of molecular syntheses, researchers wish to capitalize upon selective modification otherwise inert C-H bonds. The past two decades have witnessed considerable advances in coordination chemistry that set stage for transformative tools functionalizations. Particularly, oxidative C-H/C-H and C-H/Het-H transformations gained major attention because they avoid all elements substrate prefunctionalization. Despite advances, activations been dominated by precious transition metal catalysts based on palladium, ruthenium, iridium, rhodium, thus compromising sustainable nature overall activation approach. same holds true predominant use stoichiometric chemical oxidants regeneration active catalyst, prominently featuring hypervalent iodine(III), copper(II), silver(I) oxidants. Thereby, quantities undesired byproducts are generated, which preventive applications scale. In contrast, elegant merger homogeneous metal-catalyzed with electrosynthesis bears unique power achieve outstanding levels oxidant resource economy. Thus, contrast classical electrosyntheses control, metalla-electrocatalysis huge largely untapped potential unmet site selectivities means catalyst control. While indirect electrolysis using palladium complexes has realized, less toxic expensive base feature distinct beneficial assets toward this Account, I summarize emergence electrocatalyzed earth-abundant 3d metals beyond, a topical focus contributions from our laboratories through November 2019. cobalt electrocatalysis was identified as particularly powerful platform wealth transformations, including oxygenations nitrogenations well alkynes, alkenes, allenes, isocyanides, carbon monoxide, among others. As complementary tools, nickel, copper, very recently iron devised metalla-electrocatalyzed activations. Key success were detailed mechanistic insights, oxidation-induced reductive elimination scenarios. Likewise, development methods make weak O-coordination benefited crucial insights into catalyst's modes action experiment, operando spectroscopy, computation. Overall, thereby syntheses These electrooxidative frequently characterized improved chemoselectivities. Hence, ability dial redox at minimum level required desired transformation renders an ideal functionalization structurally complex molecules sensitive functional groups. This strategy was, inter alia, successfully applied scale-up continuous flow step-economical assembly polycyclic aromatic hydrocarbons.

Language: Английский

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C–H activation

Nature Reviews Methods Primers, Journal Year: 2021, Volume and Issue: 1(1)

Published: June 17, 2021

Language: Английский

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Photokatalyse mit sichtbarem Licht: Welche Bedeutung hat sie für die organische Synthese?

Angewandte Chemie, Journal Year: 2018, Volume and Issue: 130(32), P. 10188 - 10228

Published: Feb. 21, 2018

Abstract Die Photokatalyse mit sichtbarem Licht hat sich im letzten Jahrzehnt zu einer breit angewandten Methode in der organischen Synthese entwickelt. Für viele wichtige Reaktionen, wie Kreuzkupplungen, α‐Amino‐Funktionalisierungen, Cycloadditionen, ATRA‐Reaktionen oder Fluorierungen, wurden photokatalytische Varianten berichtet. Um Chemiker bei Auswahl photokatalytischer Methoden für ihre Synthesen unterstützen, vergleichen wir diesem Aufsatz klassische und Verfahren ausgewählte Reaktionsklassen zeigen deren Vorteile Grenzen auf. In vielen Fällen verlaufen die photokatalytischen Reaktionen unter milderen Reaktionsbedingungen, typischerweise Raumtemperatur, stöchiometrische Reagenzien werden durch einfache Oxidanzien Reduktionsmittel Luft, Sauerstoff Amine ersetzt. Beeinflusst organische Synthese? Aussicht, Elektronen Substraten Zwischenprodukten hin‐ herzuschieben Energie selektiv einen sichtbares absorbierenden Photokatalysatoren übertragen, verspricht aktuellen Radikalchemie verbessern neue Wege den Zugang reaktiven, bisher unbekannten Spezies erschließen, insbesondere das Zusammenspiel von Organo‐ Metallkatalyse.

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Transition Metal-Catalyzed Organic Reactions under Visible Light: Recent Developments and Future Perspectives

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(16), P. 9170 - 9196

Published: July 20, 2020

The development of transition metal (TM) catalysis for organic synthesis under visible light without recourse to typical photoredox catalysts has become a rapidly growing area research and been actively explored in the past several years. Distinct from extensively developed catalysis, which photocatalyst generally does not directly participate bond-forming process, photocatalyst/TM synergistic absorbs photon energy transfers TM catalyst through redox or transfer this Review focuses on summarizing recent developments photocatalytic reactions that use complexes both absorb catalytic bond formation involving covalently bonded intermediate. contents are categorized by used (Pd, Cu, Co, Ni, Mn, Au, Rh, Fe, Ru), with descending sequence according number examples reported each metal, provide an overview April 2020. Future perspectives personal opinions regarding expanding field also discussed.

Language: Английский

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sp³ C–H Arylation and Alkylation Enabled by the Synergy of Triplet Excited Ketones and Nickel Catalysts

Journal of the American Chemical Society, Journal Year: 2018, Volume and Issue: 140(38), P. 12200 - 12209

Published: Sept. 5, 2018

Triplet ketone sensitizers are of central importance within the realm photochemical transformations. Although radical-type character triplet excited states diaryl ketones suggests viability for triggering hydrogen-atom transfer (HAT) and single-electron (SET) processes, among others, their use as multifaceted catalysts in C–C bond-formation via sp3 C–H functionalization alkane feedstocks still remains rather unexplored. Herein, we unlock a modular platform forging C(sp3)–C(sp2) C(sp3)–C(sp3) linkages from abundant bonds functional handles using synergy between nickel simple, cheap ketones. This method is distinguished by its wide scope that obtained starting precursors, thus complementing existing inner-sphere protocols or recent photoredox scenarios based on iridium polypyridyl complexes. Additionally, such provides new strategy streamlining synthesis complex molecules with high levels predictable site-selectivity preparative utility. Mechanistic experiments suggest abstraction occurs HAT state. We believe this study will contribute to more systematic utilization metallaphotoredox scenarios.

Language: Английский

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