Metallaphotoredox: The Merger of Photoredox and Transition Metal Catalysis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1485 - 1542

Published: Nov. 18, 2021

The merger of photoredox catalysis with transition metal catalysis, termed metallaphotoredox has become a mainstay in synthetic methodology over the past decade. Metallaphotoredox combined unparalleled capacity for bond formation broad utility photoinduced electron- and energy-transfer processes. Photocatalytic substrate activation allowed engagement simple starting materials metal-mediated bond-forming Moreover, electron or energy transfer directly key organometallic intermediates provided novel modes entirely complementary to traditional catalytic platforms. This Review details contextualizes advancements molecule construction brought forth by metallaphotocatalysis.

Language: Английский

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Recent Advances in Pyridinium Salts as Radical Reservoirs in Organic Synthesis

ACS Catalysis, Journal Year: 2019, Volume and Issue: 9(10), P. 8943 - 8960

Published: Aug. 28, 2019

Pyridinium salts are valuable building blocks, which have been widely applied in various organic transformations during the past few decades. In particular, N-functionalized pyridinium explored as convenient radical precursors, would go through reductive single-electron transfer. As a result, chemistry of such compounds for generating carbon-, nitrogen-, and oxygen-centered radicals has witnessed, remarkable progress achieved, making it hot topic over last five years. This Review describes recent advances area concerning development reactions involving synthesis.

Language: Английский

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Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(24), P. 9264 - 9280

Published: Oct. 10, 2019

Abstract In this Review, we highlight recent advances in the understanding and design of N‐functionalized pyridinium scaffolds as redox‐active, single‐electron, functional group transfer reagents. We provide a selection representative methods that demonstrate reactivity fundamental emerging field. The these reagents can be divided into two divergent pathways: homolytic fragmentation to liberate N‐bound substituent corresponding radical or an alternative heterolytic liberates N‐centered radical. A short description elementary steps involved induced by single‐electron is also critically discussed guide readers towards processes thought occur under conditions.

Language: Английский

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Site-Selective Catalytic Deaminative Alkylation of Unactivated Olefins

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(41), P. 16197 - 16201

Published: Sept. 29, 2019

A catalytic deaminative alkylation of unactivated olefins is described. The protocol characterized by its mild conditions, wide scope, including the use ethylene as substrate, and exquisite site-selectivity pattern for both α-olefins internal olefins, thus unlocking a new platform to forge sp3-sp3 linkages, even in context late-stage functionalization.

Language: Английский

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Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(9), P. 3536 - 3543

Published: Feb. 23, 2021

As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C–C bonds. Here, we demonstrate that the combination of anodic preparation alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp2)–C(sp3) bonds, in which free aryl bromides—both readily available chemicals—can be directly used as coupling partners. This paired electrolysis reaction features broad substrate scope bearing wide gamut functionalities, was illustrated by late-stage arylation several structurally complex natural products pharmaceuticals.

Language: Английский

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Deaminative Reductive Arylation Enabled by Nickel/Photoredox Dual Catalysis

Organic Letters, Journal Year: 2019, Volume and Issue: 21(9), P. 3346 - 3351

Published: April 17, 2019

Described is a cross-electrophilic, deaminative coupling strategy harnessing Katritzky salts as new species of electrophile in Ni/photoredox dual catalytic reductive cross-coupling reactions. Distinguishing features this arylation protocol include its mild reaction conditions, high chemoselectivity, and adaptability to variety complex substrates [i.e., pyridinium derived from amines partners (hetero)aryl bromides].

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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N-Heterocyclic carbene-catalyzed deaminative cross-coupling of aldehydes with Katritzky pyridinium salts

Chemical Science, Journal Year: 2020, Volume and Issue: 11(12), P. 3192 - 3197

Published: Jan. 1, 2020

By employing an N-heterocyclic carbene (NHC) catalyst, we developed a versatile catalytic system that enables deaminative cross-coupling reactions of aldehydes with redox-active pyridinium salts.

Language: Английский

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Deaminative Reductive Cross-Electrophile Couplings of Alkylpyridinium Salts and Aryl Bromides

Organic Letters, Journal Year: 2019, Volume and Issue: 21(8), P. 2941 - 2946

Published: March 27, 2019

A nickel-catalyzed reductive cross-coupling of alkylpyridinium salts and aryl bromides has been developed using Mn as the reductant. Both primary secondary can be used, high functional group heterocycle tolerance is observed, including for protic groups. Mechanistic studies indicate formation an alkyl radical, controlling its fate was key to success this reaction.

Language: Английский

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Frustrated Lewis-Pair-Meditated Selective Single Fluoride Substitution in Trifluoromethyl Groups

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(5), P. 2572 - 2578

Published: Jan. 14, 2020

Single fluoride substitution in trifluoromethylarenes is an ongoing synthetic challenge that often leads to "over-reaction", where multiple fluorides are replaced. Development of this reaction would allow simple access a vast range difluoromethyl derivatives current interest pharmaceutical, agrochemistry, and materials sciences. Using catalytic frustrated Lewis pair approach, we have developed generic protocol allows single one trifluoromethyl groups with neutral phosphine pyridine bases. The resulting phosphonium pyridinium salts can be further functionalized via nucleophilic substitution, photoredox coupling, electrophilic transfer reactions allowing the generation array products.

Language: Английский

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