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

---

Alkoxy Radicals See the Light: New Paradigms of Photochemical Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2429 - 2486

Published: Oct. 6, 2021

Alkoxy radicals are highly reactive species that have long been recognized as versatile intermediates in organic synthesis. However, their development has impeded due to a lack of convenient methods for generation. Thanks advances photoredox catalysis, enabling facile access alkoxy from bench-stable precursors and free alcohols under mild conditions, research interest this field renewed. This review comprehensively summarizes the recent progress radical-mediated transformations visible light irradiation. Elementary steps radical generation either or central reaction development; thus, each section is categorized discussed accordingly. Throughout review, we focused on different mechanisms well impact synthetic utilizations. Notably, catalytic abundant still early stage, providing intriguing opportunities exploit diverse paradigms.

Language: Английский

---

Enantioselective Radical Reactions Using Chiral Catalysts

Chemical Reviews, Journal Year: 2022, Volume and Issue: 122(6), P. 5842 - 5976

Published: Jan. 24, 2022

Benefiting from the impressive increase in fundamental knowledge, last 20 years have shown a continuous burst of new ideas and consequently plethora catalytic methods for enantioselective radical reactions. This review aims to provide complete survey progress achieved over this latter period. The first part focuses on use chiral organocatalysts, these include catalysts covalently linked substrate those that interact with by weaker interactions like hydrogen bonds. second is devoted transition-metal redox catalysis which organized according increasing atomic number first-row transition metals (Ti, Cr, Fe, Mn, Co, Ni, Cu). Bioinspired manganese- iron-mediated hydroxylations oxidations are also discussed. A specific section dedicated reactivity Ru, Rh, Ir complexes as Lewis acids special focus at metal. Absorption photons result different events such energy transfer, single-electron hydrogen-atom transfer facilitating formation radicals. Organocatalysis has been successfully combined photocatalysts, opened pathways enlarging precursors available. merger photocatalysis organo- or metalla-photocatalysis brought novelty allowed discovery large original transformations. enzyme-catalyzed reactions involving intermediates largely benefit visible-light irradiation included review. provides comprehensive inventory goal detailing reaction mechanisms involved transformations any nonspecialist could find their own creativity invent yet unknown applications.

Language: Английский

---

Catalytic three-component dicarbofunctionalization reactions involving radical capture by nickel

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(19), P. 10836 - 10856

Published: Jan. 1, 2021

The catalytic dicarbofunctionalization of unsaturated π bonds represents a powerful platform for the rapid construction complex motifs. Despite remarkable progress, novel and efficient methods achieving such transformations under milder conditions with chemo-, regio-, stereoselectivity still remain significant challenge; thus, their development is highly desirable. Recently, merging nickel catalysis radical chemistry offers new benign unprecedented reactivity selectivity. In this review, we summarize recent advances in area by underpinning domino involving capture to provide clear overview reaction designs mechanistic scenarios.

Language: Английский

---

Transition Metal (Ni, Cu, Pd)-Catalyzed Alkene Dicarbofunctionalization Reactions

Accounts of Chemical Research, Journal Year: 2021, Volume and Issue: 54(17), P. 3415 - 3437

Published: Aug. 12, 2021

ConspectusRecently, alkene dicarbofunctionalization, i.e., the powerful organic synthesis method of difunctionalization with two carbon sources, emerged as a formidable reaction immense promise to synthesize complex molecules expeditiously from simple chemicals. This is generally achieved transition metals (TMs) through interception by sources an alkylmetal [β-H–C(sp3)–[M]] species, key intermediate prone undergo rapid β-H elimination. Related prior reports, since Paolo Chiusoli and Catellani's work in 1982 [ Tetrahedron Lett. 1982, 23, 4517], have used bicyclic disubstituted terminal alkenes, wherein elimination avoided geometric restriction or complete lack β-H's. With reasoning that β-H–C(sp3)–[M] intermediates could be rendered amenable use first row late TMs formation coordination-assisted transient metallacycles, these strategies were implemented address problem dicarbofunctionalization reactions.Because catalyze C(sp3)–C(sp3) coupling, Cu Ni anticipated impart sufficient stability intermediates, generated catalytically upon carbometalation, for their subsequent electrophiles/nucleophiles three-component reactions. Additionally, such innate property enable coupling partners entropically driven cyclization/coupling The cyclometalation concept stabilize intractable was hypothesized when reactions performed. idea curtail founded Whitesides's J. Am. Chem. Soc. 1976, 98, 6521] observation metallacycles much slower than acyclic alkylmetals.In this Account, examples demonstrate catalysts alkenylzinc reagents, alkyl halides, aryl halides afford carbo- heterocycles. In addition, forming nickellacycles enabled regioselective performance various alkenyl compounds. situ [M]-H alkenes after induced unprecedented metallacycle contraction process, which six-membered metal-containing rings shrank five-membered cycles, allowing creation new carbon–carbon bonds at allylic (1,3) positions. Applications are discussed.

Language: Английский

---

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

---

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency

Chemical Society Reviews, Journal Year: 2022, Volume and Issue: 51(6), P. 2313 - 2382

Published: Jan. 1, 2022

Visible-light photoredox catalysis has been regarded as an extremely powerful tool in organic chemistry, bringing the spotlight back to radical processes. The versatility of photocatalyzed reactions already demonstrated be effective providing alternative routes for cross-coupling well multicomponent reactions. photocatalyst allows generation high-energy intermediates through light irradiation rather than using highly reactive reagents or harsh reaction conditions. In a similar vein, electrochemistry experienced fruitful renaissance generating without need any catalyst. Such milder approaches pose basis toward higher selectivity and broader applicability. electrochemical reactions, species acts starter cascade events. This diverse reactivity use is usually not covered by classical methods. Owing availability cheaper more standardized photo- reactors, easily scalable flow-setups, it surprising that these two fields have become areas increased research interest. Keeping view, this review aimed at overview synthetic design MCRs involving and/or activation crucial step with particular focus on choice difunctionalized reagent.

Language: Английский

---

Recent advances in transition-metal-catalysed asymmetric coupling reactions with light intervention

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(22), P. 12808 - 12827

Published: Jan. 1, 2021

Transition metal-catalysed asymmetric coupling has been established as a robust tool for constructing complex organic molecules. Although this area extensively studied, the development of efficient protocols to construct stereogenic centres with excellent regio- and enantioselectivities is highly desirable remains challenging. Asymmetric transition metal catalysis light intervention provides practical alternative strategy current methods considerably expands synthetic utility result abundant feedstocks mild conditions. This tutorial review comprehensively summarizes recent advances in transition-metal-catalysed reactions intervention; particular, concise analysis substrate scope mechanistic scenarios governing stereocontrol discussed.

Language: Английский

---

Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(38), P. 15873 - 15881

Published: Sept. 20, 2021

A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) biimidazoline (BiIm) ligands revealed that enantioselectivity correlates electronic properties the ligands, more electron-donating affording higher ee's. Experimental computational mechanistic studies were conducted, lending support hypothesis elimination enantiodetermining character influences by altering position transition state structure along coordinate. study demonstrates benefits utilizing statistical modeling as platform for understanding provides new insight into an emerging class chiral Ni Ni/photoredox cross-coupling.

Language: Английский

---

Dicarbofunctionalization of [1.1.1]Propellane Enabled by Nickel/Photoredox Dual Catalysis: One-Step Multicomponent Strategy for the Synthesis of BCP-Aryl Derivatives

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(28), P. 12961 - 12969

Published: July 6, 2022

Bicyclo[1.1.1]pentane (BCP) motifs as para-disubstituted aryl bioisosteres are playing an emerging role in pharmaceutical, agrochemical, and materials chemistry. The vast majority of these structures is obtained from a BCP electrophile or nucleophile, which themselves derived [1.1.1]propellane via cleavage the internal C–C bond through addition either radicals metal-based nucleophiles. Compared with current stepwise approaches, multicomponent reaction that provides direct access to complex diverse disubstituted products would be more attractive. Herein, we report single-step, approach synthetically versatile arylated nickel/photoredox catalysis. Importantly, this three-component process allows two bonds formed single step sets three quaternary centers, unprecedented any previously reported methods. method has been demonstrated allow architectures halide radical precursor substrates.

Language: Английский

---