Potent Reductants via Electron-Primed Photoredox Catalysis: Unlocking Aryl Chlorides for Radical Coupling

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(5), P. 2093 - 2099

Published: Jan. 17, 2020

We describe a new catalytic strategy to transcend the energetic limitations of visible light by electrochemically priming photocatalyst prior excitation. This system is able productively engage aryl chlorides with reduction potentials hundreds millivolts beyond potential Na0 in productive radical coupling reactions. The radicals produced via this can be leveraged for both carbon–carbon and carbon–heteroatom bond-forming Through direct comparison, we illustrate reactivity selectivity advantages approach relative electrolysis photoredox catalysis.

Language: Английский

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Transformations of Less-Activated Phenols and Phenol Derivatives via C–O Cleavage

Chemical Reviews, Journal Year: 2020, Volume and Issue: 120(18), P. 10454 - 10515

Published: Aug. 28, 2020

Employing phenols and phenol derivatives as electrophiles for cross-coupling reactions has numerous advantages over commonly used aryl halides in terms of environmental-friendliness sustainability. In the early stage discovering such transformations, most efforts have been devoted to utilizing highly activated sulfonate types (e.g., OTf, OTs, etc.), which similar reactivities corresponding halides. However, a continuing scientific challenge is how achieve direct C-O functionalizations relatively less-activated more efficiently. this review, we will focus on recent updates derivatives, from carboxylates pivalates, acetates, carbamates carbonates, ethers (anisoles, diaryl ethers, pyridyl silyl ethers), phenolate salts, ultimately simply unprotected phenols, sorted by bond formations. Both transition-metal-catalyzed transition-metal-free protocols be covered discussed detail. Instead, sulfonates not extensively unless they are closely related, due their high reactivity. Since represent main linkages or units lignin biomass, successes transformations potentially make major contributions biomass upgrading depolymerization.

Language: Английский

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Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(29), P. 10882 - 10889

Published: July 13, 2021

We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated in situ. The combination of an isophthalonitrile photocatalyst and sodium formate promotes diverse aryl coupling reactions abundant but difficult to reduce chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled key terminal reductant byproduct, carbon dioxide anion.

Language: Английский

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Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Chlorides with Primary Alkyl Chlorides

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(22), P. 9902 - 9907

Published: May 15, 2020

Alkyl chlorides and aryl are among the most abundant stable carbon electrophiles. Although their coupling with nucleophiles is well developed, cross-electrophile of alkyl has remained a challenge. We report here first general approach to this transformation. The key productive, selective cross-coupling use small amount iodide or bromide along recently reported ligand, pyridine-2,6-bis(N-cyanocarboxamidine) (PyBCamCN). scope reaction demonstrated 35 examples (63 ± 16% average yield), we show that Br– I– additives act as cocatalysts, generating low, steady-state concentration more-reactive bromide/iodide.

Language: Английский

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Nickel-Catalyzed Reductive Cross-Couplings: New Opportunities for Carbon–Carbon Bond Formations through Photochemistry and Electrochemistry

CCS Chemistry, Journal Year: 2021, Volume and Issue: 4(1), P. 9 - 30

Published: Oct. 15, 2021

Open AccessCCS ChemistryMINI REVIEW1 Jan 2022Nickel-Catalyzed Reductive Cross-Couplings: New Opportunities for Carbon–Carbon Bond Formations through Photochemistry and Electrochemistry Liang Yi†, Tengfei Ji†, Kun-Quan Chen, Xiang-Yu Chen Magnus Rueping Yi† Institute of Organic Chemistry, RWTH Aachen University, 52074 †L. Yi T. Ji contributed equally to this work.Google Scholar More articles by author , Ji† School Chemical Sciences, University the Chinese Academy Beijing 100049 Google *Corresponding authors: E-mail Address: [email protected] King Abdullah Science Technology (KAUST), Thuwal 23955 https://doi.org/10.31635/ccschem.021.202101196 SectionsAboutAbstractPDF ToolsAdd favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Metal-catalyzed cross-electrophile couplings have become a valuable tool carbon–carbon bond formation. This minireview provides comprehensive overview recent developments in topical field couplings, explanations current state-of-the-art, highlights new opportunities arising emerging fields photoredox catalysis electrochemistry. Download figure PowerPoint Introduction Carbon–carbon formations always been one most useful reactions both industry academia gained considerable attention from many synthetic chemists who developed novel strategies achieve improved sustainable transformations. Transition metal has continually provided activation modes C–C formations1–5 fascinated long time. Many named associated with transition powerful method cross-couplings electrophiles organometallic nucleophiles (Scheme 1a). Despite progress, use reagents can cause undesired side chemical wastes. Alternatively, cross-nucleophile coupling as an efficient synthesis synthetically biologically important compounds 1b).6–8 However, lower availability carbon represents limitation. Recently, metal-catalyzed cross-coupling between two bench stable under reductive conditions emerged construction bonds. In particular, nickel (Ni) catalysts, characterized low reduction potential electronegativity, undergo rapid oxidative addition.9 As such, it is not surprising that nickel-catalyzed flourishing area organic chemistry characteristic advantages over classical synthesis, such widely available avoiding unstable time-consuming costly prefunctional processes. Scheme 1 | (a–c) cross-coupling. Thus, there significant progress development constructing The first example was published about 100 years ago Wurtz10 Tollens Fittig11 using sodium reductant mediator aryl halides alkyl halides. Stoichiometric high temperatures are needed. Therefore, functional group tolerance application limited. Another strategy electrosynthesis. Early explorations electroreductive include cross/homo-coupling halides, acyl, carboxylation cross-couplings.12 be difficult specialized laboratory equipment required. These limitations restricted further formation bonds several years. electrosynthesis recently seen renaissance cross-couplings. popular combination metallic reducing agents number Mn or Zn reductants.13–20 its success, addition scalability efficiency problems, utility powders inevitably produces excess waste. photochemical alternatives developed. impressive achievements made merging photo- electrochemistry create avoid powders. Considering construction, provide conceptual understanding 1c). Against background, we attempt give state-of-the-art highlight pathways. Alkyl–Aryl Cross-Coupling Nickel/metallic agent system viability alkyl-aryl via initially demonstrated research groups Durandetti,21 Lipshutz,22 Wangelin23 2). Specifically, Durandetti co-workers21 described α-chloroesters, well Refortmatsky reaction presence manganese metal. Lipshutz co-workers22 investigated participation zinc palladium-catalyzed halide bromide, Wangelin co-workers23 reported cobalt-catalyzed early examples combined metal/reducing systems construct milder conditions. 2 reporting catalysis. recently, more recognized general concept actively researched exciting 2010, Weix co-workers24 Ni/Mn selective equimolar quantities halide. High cross-selectivities were achieved bipyridyl phosphine ligand 3a). 3 Overview alkyl–aryl protocol, stoichiometric required, broad range tolerated. drawback, secondary bromides resulted mixed isomer products. Nevertheless, direct without intermediate organomanganese species protocol. Regarding mechanism 3b), postulated key step valent Ni(0) generates Ar–Ni(II) I. Subsequent radical affords Ar–Ni(III)–R II. Finally, elimination II desired product Ni(I) III, which could produce single-electron transfer (SET) halogen-atom abstraction. Reduction III finishes catalytic cycle. Concurrently, similar results cobalt/phosphine disclosed Amatore Gosmini25 electron-deficient bromides. After these studies, great efforts focused on different 3c).26–38 Notably, Molander co-workers39,40 successfully expanded installation fragments onto pharmaceutically relevant heterocyclic motifs. A variety aliphatic tosylates underwent moderate good yields, furnishing substituted heteroaromatic compounds. achievements, alkylamines, abundant natural feedstocks, had realized until recently. 2017, Watson co-workers41 Suzuki–Miyaura boronic acids, employing Katritzky salts C-centered-radical precursors. Very Rueping,42 Watson,43 Martin,44 Han45 independently applied cases, employed optimal reductants elevated usually Han’s Ni/Zn enabled wider substrate scope including bromoalkynes Although primary developed, tertiary easy due dominant β-hydride reaction. 2015, Gong co-workers46 resolved issue pyridine (Py) 4-(N,N-dimethylamino)pyridine (DMAP) carbene salt additives suppress enhance 4). tolerated various better obtained electron-withdrawing substituents. 4 Until now, cases form at ipso-carbon where regioselectivity less explored 5a). An migratory Zhu co-workers47 2017 5b). proceeded smoothly Ni(ClO4)2(H2O)6/6,6′-dimethyl-2,2′-bipyridyl catalyst nonactivated affording 1,1-diarylalkane derivatives, widespread products active molecules, excellent yields regioselectivity. 5 Nickel-catalyzed proposed transformation 5c. Initially, inactivated bromide leads Ni(II) complex following insertion steps deliver thermodynamically benzylic-Ni(I) III. Then, Ni(III) IV. Ni(I)-X V. then reduced powder close class also Yin co-workers,48 NiI2/bathocuproine reductant. Interestingly, opposite proposed. step, rather than I′. chain process II′ generated SET Ni(I)−X ( IV′). Several control experiments trapping carried out support their mechanism. electrophiles, types cross-couplings, enable modes, still highly desirable. During last few years, metal/photoredox dual witnessed remarkable offered unconventional transformations.49–65 To date, strongly dominated redox neutral pathway, wherein nucleophile partner changes oxidation state nickel/photoredox offers alternative absence 6). 6 representation pathway Nickel-photoredox 2016, MacMillan co-workers66–68 catalyzed 7a). Ni/photoredox mechanism, Concomitantly, hydrogen-atom abstraction tris(trimethylsilyl)silane (TTMSS) bromine radicals forms stabilized silyl intermediate. mediated radical, binds I, leading photo Ir(II). case, photoexcited generate radical. 7 (a–d) Lei co-workers,69 studies MacMillan, Et3N terminal 7b. complex. At same time, low-valent resulting intercepted species. species, Ir(II) cycles. used Vannucci co-workers,70 triethanolamine Based previous developments, Jensen co-workers71 continuously stirred-tank reactor platform flow. gram-scale after 13 h, opened up applications system. related approach Brill co-workers72 assembly drug-like benzylic chlorides (hetero)aryl continuous flow highlighting industrial applicability. Furthermore, co-workers73 bathocuproine 7c). Compared iodides, simple abundant, inexpensive, readily methods. they electrophilic partners nucleophilic aromatic substitutions. chlorides. involving substrates, aminosilane reductant, NiCl2(bim) Ir-based photocatalyst, afforded C(sp2)−C(sp3) coupled generally 7d).74 context series salts, aziridines, epoxides. co-workers,75 identified C(sp3) 4CzIPN photocatalyst NiBr2(DME)/4,4′-di-tert-butylbipyridine (dtbbpy) catalyst, differently substrates 8a). 8 (a–f) Doyle co-workers32 nickel/Mn-catalyzed styrenyl aziridines iodides. drawback aziridine did work 8b). study co-workers76 constituted strategy. Their way newly showed scope. iodides NiBr2(DME)/dtbbpy catalyst. able cyclic classic methods, 8c). 8d. iodide β-iodoamine IV formed ring-opening aziridine. Subsequently, 4CzIPN−• Ni(I)−I III). I Then [4-CzIPN]−• nickel/Mn gave MnI2 instead β-iodoamine; thus, no obtained. Continued co-workers77 epoxides 8e). Ni/Ti/photoredox Various styrene oxides, epoxides, all reacted regioselectivities. Allylic carbonates proven suitable cross-couplings.78–80 nice Chu co-workers81 allylic vinyl triflates 8f). E- Z-configured 1,4-dienes choice photocatalysts. When Ir(ppy)2(dtbbpy)+ photoinduced contra-thermodynamic E→Z isomerization would occur (Z)-1,4-diene product.81 strategies, them rely potentials photocatalysts furnish addition, appealing when considering toxicity cost photoactive electron-donor-acceptor (EDA) allows generation mild based-photocatalysts dyes. strategy, co-workers82 EDA N-hydroxyphthalimide (NHPI) esters. proceeds NHPI ester Hantzsch (HE), upon radiation-induced (eq 1).82 Electrochemical may offer economical Recent ability bond-forming reactions. Within area, electrochemically induced integrating 9). seminal chloroesters electrochemical strategy.12 breakthrough very Hansen co-workers83 10a). sacrificial anode tuning found crucial cooperative circumvented need temperatures. exhibited generality. 9 10 aryl–alkyl Further Bio co-workers84 Hansen’s method, esters source amine divided cell 10b). Later, one-pot C(sp2)–C(sp3) Loren co-workers85 10c), redox-active situ carboxylates tetramethyluronium hexafluorophosphate. Sevov co-workers86 shuttles protect reduction, thus improving suppressing side-product 10d). across wide aryl, heteroaryl, Given importance concurrently, Rueping87 Mei88 11a). Both methods scope, giving rise corresponding derivatives yields. experimental density theory (DFT) co-workers87 plausible 11b). 11 (a b) cathode surface. gives Ar−Ni(I) occurs Ar−Ni(II)−Br cathodic will benzylic-Ni(II) release regenerate Ni(0). Aryl–Aryl Cross-Couplings comparison bonds, C(sp2)–C(sp2) challenging result subtle difference electrophiles. 2008, Gosmini89 unsymmetrical biaryl success reactivity profiles allowed extended 2-halopyridine group.90 co-workers91 selectivities controlled catalysts electronic properties reports 12a). Mechanistically, react exclusively Pd(0) Pd(II) transmetalation complex, Ar1–Pd(II)–Ar2 IV, asymmetrical biaryls. additive potassium fluoride (KF) achieving selectivity, presumably selectivity palladium triflate bromide. Olivares Weix92 other triflates, triflates,93 tosylates,94 ortho-fluoro-substituted amides,95 difluoromethyl 2-pyridyl sulfone,96 bromides, 2,2-difluorovinyl tosylate.97 12 aryl–aryl co-workers98 polyfluorinated arenes 12b). protocol opens entry multifluorinated starts generating [C5F5N]•− C5F5N, trapped II′. III′, Also, Ni(0)/Ni(I)/Ni(III)/Ni(I) cycle possible, involves Ni(I)–C5F4N IV′) Besides aryl-heteroarybond regard, Léonel co-workers99–102 heteroaryls, 3-chloro-6-methoxypyridazines, 3-amino-6-chloropyridazines, chloropyrimidines 12c). Alkyl–Alkyl discussed above,

Language: Английский

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Metal-catalysed C–Het (F, O, S, N) and C–C bond arylation

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(16), P. 8903 - 8953

Published: Jan. 1, 2021

The formation of C–aryl bonds has been the focus intensive research over last decades for construction complex molecules from simple, readily available feedstocks.

Language: Английский

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Iron-catalysed reductive cross-coupling of glycosyl radicals for the stereoselective synthesis of C-glycosides

Nature Synthesis, Journal Year: 2022, Volume and Issue: 1(3), P. 235 - 244

Published: Feb. 17, 2022

Language: Английский

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Elucidating electron-transfer events in polypyridine nickel complexes for reductive coupling reactions

Nature Catalysis, Journal Year: 2023, Volume and Issue: 6(3), P. 244 - 253

Published: March 9, 2023

Language: Английский

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Multimetallic-Catalyzed C–C Bond-Forming Reactions: From Serendipity to Strategy

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(12), P. 6596 - 6614

Published: March 13, 2023

The use of two or more metal catalysts in a reaction is powerful synthetic strategy to access complex targets efficiently and selectively from simple starting materials. While capable uniting distinct reactivities, the principles governing multimetallic catalysis are not always intuitive, making discovery optimization new reactions challenging. Here, we outline our perspective on design elements using precedent well-documented C–C bond-forming reactions. These strategies provide insight into synergy compatibility individual components reaction. Advantages limitations discussed promote further development field.

Language: Английский

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Dynamic Kinetic Cross-Electrophile Arylation of Benzyl Alcohols by Nickel Catalysis

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 143(1), P. 513 - 523

Published: Dec. 28, 2020

Catalytic transformation of alcohols via metal-catalyzed cross-coupling reactions is very important, but it typically relies on a multistep procedure. We here report dynamic kinetic approach for the direct functionalization alcohols. The feasibility this strategy demonstrated by nickel-catalyzed cross-electrophile arylation reaction benzyl with (hetero)aryl electrophiles. proceeds broad substrate scope both coupling partners. electron-rich, electron-poor, and ortho-/meta-/para-substituted electrophiles (e.g., Ar–OTf, Ar–I, Ar–Br, inert Ar–Cl) all coupled well. Most functionalities, including aldehyde, ketone, amide, ester, nitrile, sulfone, furan, thiophene, benzothiophene, pyridine, quinolone, Ar–SiMe3, Ar–Bpin, Ar–SnBu3, were tolerated. nature method enables benzylic alcohol in presence various nucleophilic groups, nonactivated primary/secondary/tertiary alcohols, phenols, free indoles. It thus offers robust alternative to existing methods precise construction diarylmethanes. synthetic utility was concise synthesis biologically active molecules its application peptide modification conjugation. Preliminary mechanistic studies revealed that situ formed oxalates nickel, possibly radical process, an initial step aryl

Language: Английский

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