- Luminescent solar concentrators based on thermally activated delayed fluorescence dyes
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Thermally activated delayed fluorescence (TADF) dyes are third-generation light emitting materials. With impressive photophysical properties, TADF dyes are now widely recognized as successful emitters in organic light emitting diodes (OLEDs). However, their use in photovoltaic applications has not been realized. In this study, we for the first time present a TADF dye based luminescent solar concentrator device for efficient sunlight harvesting. We synthesized two carbazole dicyanobenzene (CDCB) derivative dyes and employed them in a bulk LSC device. Due to the charge transfer characteristics and twisted structures, TADF dyes help to achieve reduced reabsorption losses in the LSC. The photovoltaic measurements showed that the optical conversion efficiency (ηopt) and power conversion efficiency (ηPCE) of the champion device are 10.4% and 2.2%, respectively. Additionally, the superior resistance against photodegradation of TADF dyes facilitates their long-term use in LSCs. The results demonstrate that TADF dye-based LSCs provide a promising route for high-efficiency and low-cost solar energy generation.
- Hong, Sung-Kyu,Lee, Sae Youn,Mateen, Fahad
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Read Online
- Photocatalytic intermolecular carboarylation of alkenes by selective C-O bond cleavage of diarylethers
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Disclosed herein is a novel radical-mediated intermolecular carboarylation of alkenes by cleaving inert C-O bonds. The strategically designed arylbenzothiazolylether diazonium salts are harnessed as dual-function reagents. A vast array of alkenes are proven to be suitable substrates. The benzothiazolyl moiety in the products serves as the formyl precursor, and the OH residue provides the cross-coupling site for further product elaboration, indicating the robust transformability of the products.
- Ji, Meishan,Chang, Chenyang,Wu, Xinxin,Zhu, Chen
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Read Online
- Development of Thermally Activated Delayed Fluorescence Materials with Shortened Emissive Lifetimes
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We have prepared a thermally activated delayed fluorescence (TADF) capable molecular system carrying halogen substituents at the carbazole units. The attachment of the halogen atoms considerably decreases the half-life of the delayed fluorescence. The effect is significant. The heavier the halogen, the greater the effect. Our materials have the shortest reported emissive lifetimes for TADF achieved to date. Intersystem crossing (ISC) is improved through the heavy atom effect, yet high quantum yields are achieved both in solution as well as in thin doped films. The simple and efficient synthesis of our targets uses inexpensive and easily obtained starting materials.
- Kretzschmar, Andreas,Patze, Christian,Schwaebel, S. Thimon,Bunz, Uwe H. F.
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Read Online
- Visible-light-initiated 4CzIPN catalyzed multi-component tandem reactions to assemble sulfonated quinoxalin-2(1H)-ones
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A mild and efficient photochemical multi-component tandem reaction of quinoxalin-2(1H)-ones, alkenes and sulfinic acids is reported. This tandem reaction could be conveniently carried out at room temperature by employing 4CzIPN as the metal-free photocata
- Wang, Zhiwei,Liu, Qishun,Liu, Ruisheng,Ji, Zhongyin,Li, Yan,Zhao, Xiaohui,Wei, Wei
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supporting information
p. 1479 - 1482
(2021/09/06)
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- Solvent-Minimized Synthesis of 4CzIPN and Related Organic Fluorophores via Ball Milling
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The mechanochemical synthesis of 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile and related organic fluorophores/photocatalysts via a solvent-minimized four-fold SNAr pathway is herein described. Employing sodium tert-butoxide as base, and negating the need for any air/moisture-sensitive reaction set-ups, a selection of organic dyes was synthesized in just 1 h using this ball-milling technique. Furthermore, the transformation was then showcased on a multigram scale.
- Leitch, Jamie A.,Smallman, Harry R.,Browne, Duncan L.
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supporting information
p. 14095 - 14101
(2021/07/31)
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- A Unified Strategy to Access 2- And 4-Deoxygenated Sugars Enabled by Manganese-Promoted 1,2-Radical Migration
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The selective manipulation of carbohydrate scaffolds is challenging due to the presence of multiple, nearly chemically indistinguishable O-H and C-H bonds. As a result, protecting-group-based synthetic strategies are typically necessary for carbohydrate modification. Here we report a concise semisynthetic strategy to access diverse 2- and 4-deoxygenated carbohydrates without relying on the exhaustive use of protecting groups to achieve site-selective reaction outcomes. Our approach leverages a Mn2+-promoted redox isomerization step, which proceeds via sugar radical intermediates accessed by neutral hydrogen atom abstraction under visible light-mediated photoredox conditions. The resulting deoxyketopyranosides feature chemically distinguishable functional groups and are readily transformed into diverse carbohydrate structures. To showcase the versatility of this method, we report expedient syntheses of the rare sugars l-ristosamine, l-olivose, l-mycarose, and l-digitoxose from commercial l-rhamnose. The findings presented here validate the potential for radical intermediates to facilitate the selective transformation of carbohydrates and showcase the step and efficiency advantages attendant to synthetic strategies that minimize a reliance upon protecting groups.
- Carder, Hayden M.,Suh, Carolyn E.,Wendlandt, Alison E.
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supporting information
p. 13798 - 13805
(2021/09/07)
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- SELECTIVE VALORIZATION OF BIOMASS SUGARS
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Disclosed are methods of forming an epimer or a dehydrated isomer of a pyranose monosaccharide or a pyranose saccharide residue in an oligosaccharide or a glycoside.
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Page/Page column 23; 28-29
(2021/06/26)
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- Late Stage Phosphotyrosine Mimetic Functionalization of Peptides Employing Metallaphotoredox Catalysis
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Access to phosphotyrosine (pTyr) mimetics requires multistep syntheses, and therefore late stage incorporation of these mimetics into peptides is not feasible. Here, we develop and employ metallaphotoredox catalysis using 4-halogenated phenylalanine to afford a variety of protected pTyr mimetics in one step. This methodology was shown to be tolerant of common protecting groups and applicable to the late stage pTyr mimetic modification of protected and unprotected peptides, and peptides of biological relevance.
- Brzozowski, Martin,Chen, Hao,Mao, Runyu,Nguyen, Nghi H.,Sleebs, Brad E.
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supporting information
p. 4244 - 4249
(2021/06/28)
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- Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides
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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 radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.,Williams, Oliver P.,Yeung, Charles S.
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supporting information
p. 10882 - 10889
(2021/07/31)
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- Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**
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Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)?N and C(sp2)?O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.
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supporting information
p. 21418 - 21425
(2021/08/25)
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- Synthesis of chiral branched allylamines through dual photoredox/nickel catalysis
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Allylamines are versatile building blocks in the synthesis of various naturally occurring products and pharmaceuticals. In contrast to terminal allylamines, the methods of synthesis of their branched congeners with internal, stereodefined double bonds are less explored. This work describes a new approach for the preparation of allylaminesviacross-coupling of alkyl bromides with simple 3-bromoallylamines by merging the photoredox approach and Ni catalysis. The reaction proceeds under mild conditions, under blue light irradiation, and in the presence of an organic dye, 4CzIPN, as a photocatalyst. The scope of suitable reaction partners is broad, including alkyl bromides bearing reactive functionalities (e.g., esters, nitriles, aldehydes, ketones, epoxides) andN-protected allylamines, as well asN-allylated secondary and tertiary amines and heterocycles. The employment of non-racemic starting materials allows for rapid and easy construction of complex multifunctional allylamine derivatives without the loss of enantiomeric purity.
- Garbacz, Mateusz,Stecko, Sebastian
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supporting information
p. 8578 - 8585
(2021/10/20)
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- Photosubstitution in Dicyanobenzene-based Photocatalysts
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We report the photosubstitution of one cyano group in dicyanobenzene-based photocatalysts and thermally activated delayed fluorescence (TADF) emitters. The reaction is a general degradation pathway for some widely used organic photocatalysts such as 4CzIPN and suggests that the active photocatalyst in many reactions is likely different from 4CzIPN. On the contrary, photosubstitution is a facile route to diverse highly reducing photocatalysts and blue TADF emitters.
- Grotjahn, Sascha,K?nig, Burkhard
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supporting information
p. 3146 - 3150
(2021/05/04)
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- Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**
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Ethynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl-substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX-mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C?H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.
- Amos, Stephanie G. E.,Cavalli, Diana,Le Vaillant, Franck,Waser, Jerome
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supporting information
p. 23827 - 23834
(2021/09/25)
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- 4CzIPN-tBu-Catalyzed Proton-Coupled Electron Transfer for Photosynthesis of Phosphorylated N-Heteroaromatics
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2,4,5,6-Tetrakis(3,6-di-tert-butyl-9H-carbazol-9-yl)isophthalonitrile (4CzIPN-tBu) was developed as a photocatalyst for the phosphorus-radical-initiated cascade cyclization reaction of isocyanides. By using 4CzIPN-tBu as catalyst, we developed a visible-light-induced proton-coupled electron transfer strategy for the generation of phosphorus-centered radicals, via which a wide range of phosphorylated phenanthridines, quinolines, and benzothiazoles were successfully constructed.
- Liu, Yan,Chen, Xiao-Lan,Li, Xiao-Yun,Zhu, Shan-Shan,Li, Shi-Jun,Song, Yan,Qu, Ling-Bo,Yu, Bing
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supporting information
p. 964 - 972
(2021/01/12)
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- Nickel/Photoredox-Catalyzed Asymmetric Reductive Cross-Coupling of Racemic α-Chloro Esters with Aryl Iodides
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A unique nickel/organic photoredox co-catalyzed asymmetric reductive cross-coupling between α-chloro esters and aryl iodides is developed. This cross-electrophile coupling reaction employs an organic reductant (Hantzsch ester), whereas most reductive cross-coupling reactions use stoichiometric metals. A diverse array of valuable α-aryl esters is formed under these conditions with high enantioselectivities (up to 94 %) and good yields (up to 88 %). α-Aryl esters represent an important family of nonsteroidal anti-inflammatory drugs. This novel synergistic strategy expands the scope of Ni-catalyzed reductive asymmetric cross-coupling reactions.
- Guan, Haixing,Mao, Jianyou,Walsh, Patrick J.,Zhang, Qianwen
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supporting information
p. 5172 - 5177
(2020/02/20)
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- Tailorable carbazolyl cyanobenzene-based photocatalysts for visible light-induced reduction of aryl halides
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Herein, a series of carbazolyl cyanobenzene (CCB)-based organic photocatalysts with a broad range of photoredox capabilities were designed and synthesized, allowing precise control of the photocatalytic reactivity for the controllable reduction of aryl halides via a metal-free process. The screened-out CCB (5CzBN), a metal-free, low-cost, scalable and sustainable photocatalyst with both strong oxidative and reductive ability, exhibits superior performance for both dehalogenation and C[sbnd]C bond-forming arylation reactions.
- Ou, Wei,Zou, Ru,Han, Mengting,Yu, Lei,Su, Chenliang
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supporting information
p. 1899 - 1902
(2019/12/27)
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- Photocatalytic α-Tertiary Amine Synthesis via C?H Alkylation of Unmasked Primary Amines
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A practical, catalytic entry to α,α,α-trisubstituted (α-tertiary) primary amines by C?H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 percent atom-economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α-tertiary amines, or their corresponding γ-lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α-tertiary primary amines.
- Alder, Catherine M.,Ballantyne, George,Cresswell, Alexander J.,Cunningham, William B.,Edwards, Lee J.,Grayson, Matthew N.,Kinsella, Anna G.,McKay, Blandine S. J.,Mules, Tom,Ryder, Alison S. H.,Turner-Dore, Jacob
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supporting information
p. 14986 - 14991
(2020/06/20)
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- Organophotoredox-Mediated Amide Synthesis by Coupling Alcohol and Amine through Aerobic Oxidation of Alcohol
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The combination of an organic photocatalyst [4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6 dicyanobenzene) or 5MeOCzBN (2,3,4,5,6-pentakis(3,6-dimethoxy-9 H-carbazol-9-yl)benzonitrile)], quinuclidine, and tetra-n-butylammonium phosphate (hydrogen-bonding catalyst) was employed for amide bond formations. The hydrogen-bonded OH group activated the adjacent C?H bond of alcohols towards hydrogen atom transfer (HAT) by a radical species. The quinuclidinium radical cation, generated through single-electron oxidation of quinuclidine by the photocatalyst, employed to abstract a hydrogen atom from the α-C?H bond of alcohols selectively due to a polarity effect-produced α-hydroxyalkyl radical, which subsequently converted to the corresponding aldehyde under aerobic conditions. Then the coupling of the aldehyde and an amine formed a hemiaminal intermediate that upon photocatalytic oxidation produced the amide.
- Samanta, Samya,Shah, Sk. Sheriff,Shee, Maniklal,Singh, Amit Kumar,Singh, N. D. Pradeep,Venkatesh, Yarra
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supporting information
(2020/03/05)
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- Direct Oxygenation of C-H Bonds through Photoredox and Palladium Catalysis
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This report presents the oxygenation of C-H bonds via the merger of photocatalysis and Pd catalysis. Herein, we describe the utilization of a photocatalyst to oxidize an organopalladium(II) intermediate to high-valent PdIII or PdIV intermediates, which promotes the formation of C-O bonds. The demonstrated method works efficiently with various directing groups, such as oxime ether and benzothiazole. The applicability of this direct C-O bond formation method is shown by synthesizing several metal complexes of 2-(benzo[d]thiazol-2-yl)phenol that can be used in organic light-emitting diodes and pharmaceuticals.
- Paul, Amrita,Shah, Sk. Sheriff,Shee, Maniklal,Singh, Amit Kumar,Singh, N. D. Pradeep
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p. 3426 - 3439
(2020/03/23)
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- Photocatalytic Conversion of Benzyl Alcohols/Methyl Arenes to Aryl Nitriles via H-Abstraction by Azide Radical
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This report presents the visible-light-assisted synthesis of aryl nitriles from easily accessible alcohols or methyl arenes in the presence of O2. Organic photoredox catalyst, 4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene), induces single electron transfer (SET) from azide N3? and generates azide radical N3?.The photogenerated N3? abstracts H atom from α-C?H bond of benzylic system, which provides aldehyde and hydrazoic acid (HN3) in situ. This reaction subsequently forms azido alcohol intermediate that transforms into nitrile with the assistance of triflic acid (Br?nsted acid). A range of alcohols and methyl arenes successfully underwent cyanation at room temperature with good to excellent yields and showed good functional group tolerance.
- Shee, Maniklal,Shah, Sk. Sheriff,Singh, N. D. Pradeep
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supporting information
p. 14070 - 14074
(2020/10/12)
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- The Synthesis of Chiral Allyl Carbamates via Merger of Photoredox and Nickel Catalysis
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A mild, and versatile, organophotoredox/Ni-mediated protocol was developed for the direct preparation of diverse, enantioenriched allyl carbamates. The reported approach represents a significant departure from classical step-by-step synthesis of allyl carbamates. This dual photoredox/Ni based strategy offers unrivalled capacity for convergent unification of readily available alkyl halides and chiral carbamates derived from 1-bromo-alken-3-ols with high chemoselectivity and efficiency. The reported photoredox/Ni catalyzed cross-coupling reaction is not limited to carbamates, but also to other O-derivatives such as esters, ethers, acetals, carbonates or silyl ethers. To demonstrate the utility of the reported protocol, the resulting allyl carbamates were transformed into functionalized non-racemic allylamines through a sigmatropic rearrangement reaction in enantiospecific manner. This approach allowed for synthesis of enantiomeric allylamines by a simple control of the geometry of a double bond of allyl carbamates. (Figure presented.).
- Garbacz, Mateusz,Stecko, Sebastian
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supporting information
p. 3213 - 3222
(2020/07/06)
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- Synthesis of Aliphatic Amides through a Photoredox Catalyzed Radical Carbonylation Involving Organosilicates as Alkyl Radical Precursors
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Alkyl radicals, from primary to tertiary, formed by photocatalyzed oxidation of organosilicates, are involved efficiently in radical carbonylation with carbon monoxide (CO), in the presence of various amines and CCl4, leading to a variety of amides in moderate to good yields. (Figure presented.).
- Cartier, Alex,Levernier, Etienne,Dhimane, Anne-Lise,Fukuyama, Takahide,Ollivier, Cyril,Ryu, Ilhyong,Fensterbank, Louis
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supporting information
p. 2254 - 2259
(2020/05/06)
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- C(sp3)?C(sp3) Cross-Coupling of Alkyl Bromides and Ethers Mediated by Metal and Visible Light Photoredox Catalysis
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We report a C(sp3)?C(sp3) cross-coupling of alkyl bromides and alkyl chlorides with ethers by dual photoredox-nickel catalysis. The catalytic system comprises of the organic photocatalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4-CzIPN) and bench stable nickel (II) acetylacetonate in the presence of visible-light, providing the coupling products in up to 92% yield. Preliminary mechanistic studies suggest two catalytic cycles, as well as the photogeneration of bromine or chlorine radicals from halide atoms that are present in the structures of the coupling partners. The halide radical mediates the hydrogen atom transfer event, avoiding the need of an additional HAT catalyst. (Figure presented.).
- Santos, Marilia S.,Corrêa, Arlene G.,Paix?o, Márcio W.,K?nig, Burkhard
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supporting information
p. 2367 - 2372
(2020/05/08)
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- Organophotoredox assisted cyanation of bromoarenes: via silyl-radical-mediated bromine abstraction
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The insertion of a nitrile (-CN) group into arenes through the direct functionalization of the C(sp2)-Br bond is a challenging reaction. Herein, we report an organophotoredox method for the cyanation of aryl bromides using the organic photoredox catalyst 4CzIPN and tosyl cyanide (TsCN) as the nitrile source. A photogenerated silyl radical, via a single electron transfer (SET) mechanism, was employed to abstract bromine from aryl bromide to provide an aryl radical, which was concomitantly intercepted by TsCN to afford the aromatic nitrile. A range of substrates containing electron-donating and -withdrawing groups was demonstrated to undergo cyanation at room temperature in good yields.
- Shah, Sk. Sheriff,Shee, Maniklal,Singh, N. D. Pradeep
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supporting information
p. 4240 - 4243
(2020/04/22)
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- Carbonylation of Alkyl Radicals Derived from Organosilicates through Visible-Light Photoredox Catalysis
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Primary, secondary, and tertiary alkyl radicals formed by the photocatalyzed oxidation of organosilicates underwent efficient carbonylation with carbon monoxide (CO) to give a variety of unsymmetrical ketones. This study introduces the possibility of radi
- Cartier, Alex,Levernier, Etienne,Corcé, Vincent,Fukuyama, Takahide,Dhimane, Anne-Lise,Ollivier, Cyril,Ryu, Ilhyong,Fensterbank, Louis
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supporting information
p. 1789 - 1793
(2019/01/09)
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- Cobalt-Catalyzed Allylic Alkylation Enabled by Organophotoredox Catalysis
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Co-catalyzed allylic substitution reactions have received little attention, arguably because of the lack of any known advantage of Co catalysis over either Rh or Ir catalysis. Described here is a general and regioselective Co-catalyzed allylic alkylation using an in situ catalyst activation by organophotoredox catalysis. This noble-metal-free catalytic system exhibits unprecedentedly high reactivities and regioselectivities for the allylation with an allyl sulfone, for the first time, representing the unique synthetic utility of the Co-catalyzed method compared to the related Rh- and Ir-catalyzed reactions.
- Takizawa, Koji,Sekino, Tomoyuki,Sato, Shunta,Yoshino, Tatsuhiko,Kojima, Masahiro,Matsunaga, Shigeki
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supporting information
p. 9199 - 9203
(2019/06/04)
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- C-Terminal Bioconjugation of Peptides through Photoredox Catalyzed Decarboxylative Alkynylation
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We report the first decarboxylative alkynylation of the C-terminus of peptides starting from free carboxylic acids. The reaction is fast, metal-free, and proceeds cleanly to afford alkynylated peptides with a broad tolerance for the C-terminal amino acid. By the use of hypervalent iodine reagents, the introduction of a broad range of functional groups was successful. C-terminal selectivity was achieved by differentiation of the oxidation potentials of the carboxylic acids based on the use of fine-tuned organic dyes.
- Garreau, Marion,Le Vaillant, Franck,Waser, Jerome
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supporting information
p. 8182 - 8186
(2019/05/21)
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- Enantioselective Synthesis of N-Benzylic Heterocycles: A Nickel and Photoredox Dual Catalysis Approach
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Reported herein is a dual nickel- and photoredox-catalyzed modular approach for the preparation of enantioenriched N-benzylic heterocycles. α-Heterocyclic carboxylic acids, easily obtainable from common commercial material, are reported as suitable substrates for a decarboxylative strategy in conjunction with a chiral pyridine-oxazoline (PyOx) ligand, providing quick access to enantioenriched drug-like products. The presence of a directing group on the heterocyclic moiety is shown to be beneficial, affording improved stereoselectivity in a number of cases.
- Pezzetta, Cristofer,Bonifazi, Davide,Davidson, Robert W. M.
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supporting information
p. 8957 - 8961
(2019/11/11)
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- Visible-light mediated carbamoyl radical addition to heteroarenes
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The generation of carbamoyl radicals, followed by their addition to heteroarenes, was performed under mild conditions through a metal-free photocatalyzed decarboxylation of oxamic acids. The process has been applied to the carbamoylation of heteroaromatic bases using α-aminoacid-derived oxamic acids, leading to the corresponding amides without racemization.
- Jatoi, Ashique Hussain,Pawar, Govind Goroba,Robert, Frédéric,Landais, Yannick
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supporting information
p. 466 - 469
(2019/01/10)
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- Deuterated organic compound, mixture and composition containing said compound, and organic electronic device
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The present disclosure discloses a deuterated organic compound and a formulation and an organic electronic device containing the same, wherein the deuterated organic compound has the following structural formula: wherein Ar is an aromatic or heteroaromatic structural unit, D is an electron donor group, A is an electron acceptor group, n and m are an integer between 1 and 6; and wherein for the organic compound, (S1?T1)≤0.25 eV, and at least one H atom of the organic compound is substituted by deuterium. The present disclosure achieves the improvement of the electroluminescence quantum efficiency and the lifetime of the organic compound by replacing the H atom in the organic compound with deuterium and having (S1?T1)≤0.35 eV, and the material of the present disclosure has a great application potential and application range due to its low cost and relatively simple synthesis process.
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Page/Page column 41; 42
(2019/07/03)
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- Metallaphotoredox-Mediated Csp2-H Hydroxylation of Arenes under Aerobic Conditions
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The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc)2 as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-state intramolecular proton transfer properties for generating tunable luminescence responses.
- Shah, Sk. Sheriff,Paul, Amrita,Bera, Manoranjan,Venkatesh, Yarra,Singh, N. D. Pradeep
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supporting information
p. 5533 - 5536
(2018/09/21)
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- A Fully Automated Continuous-Flow Platform for Fluorescence Quenching Studies and Stern–Volmer Analysis
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Herein, we report the first fully automated continuous-flow platform for fluorescence quenching studies and Stern–Volmer analysis. All the components of the platform were automated and controlled by a self-written Python script. A user-friendly software allows even inexperienced operators to perform automated screening of novel quenchers or Stern–Volmer analysis, thus accelerating and facilitating both reaction discovery and mechanistic studies. The operational simplicity of our system affords a time and labor reduction over batch methods while increasing the accuracy and reproducibility of the data produced. Finally, the applicability of our platform is elucidated through relevant case studies.
- Kuijpers, Koen P. L.,Bottecchia, Cecilia,Cambié, Dario,Drummen, Koen,K?nig, Niels J.,No?l, Timothy
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supporting information
p. 11278 - 11282
(2018/08/11)
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- Fine-tuned organic photoredox catalysts for fragmentation-alkynylation cascades of cyclic oxime ethers
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Fine-tuned organic photoredox catalysts are introduced for the metal-free alkynylation of alkylnitrile radicals generated via oxidative ring opening of cyclic alkylketone oxime ethers. The redox properties of the dyes were determined by both cyclic voltam
- Le Vaillant, Franck,Garreau, Marion,Nicolai, Stefano,Gryn'Ova, Ganna,Corminboeuf, Clemence,Waser, Jerome
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p. 5883 - 5889
(2018/07/25)
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- Visible-light photocatalyzed oxidative decarboxylation of oxamic acids: a green route to urethanes and ureas
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A sustainable metal-free route to urethanes and ureas based on a photocatalyzed oxidative decarboxylation of oxamic acids is described. The reaction includes in situ generation of an isocyanate from the oxamic acid, using an organic dye as a photocatalyst, a hypervalent iodine reagent as an oxidant and a light source, which trigger the free-radical decarboxylation. This protocol successfully avoids the isolation, purification and storage of carcinogenic isocyanates and allows elaboration of urethanes and ureas in a one-pot process from commercially available sources.
- Pawar, Govind Goroba,Robert, Frédéric,Grau, Etienne,Cramail, Henri,Landais, Yannick
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supporting information
p. 9337 - 9340
(2018/08/31)
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- Organic photocatalysis for the radical couplings of boronic acid derivatives in batch and flow
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We report an acridium-based organic photocatalyst as an efficient replacement for iridium-based photocatalysts to oxidise boronic acid derivatives by a single electron process. Furthermore, we applied the developed catalytic system to the synthesis of four active pharmaceutical ingredients (APIs). A straightforward scale up approach using continuous flow photoreactors is also reported affording gram an hour throughput.
- Lima, Fabio,Grunenberg, Lars,Rahman, Husaini B. A.,Labes, Ricardo,Sedelmeier, Joerg,Ley, Steven V.
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supporting information
p. 5606 - 5609
(2018/06/04)
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- Visible-Light-Promoted Nickel- and Organic-Dye-Cocatalyzed Formylation Reaction of Aryl Halides and Triflates and Vinyl Bromides with Diethoxyacetic Acid as a Formyl Equivalent
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A simple formylation reaction of aryl halides, aryl triflates, and vinyl bromides under synergistic nickel- and organic-dye-mediated photoredox catalysis is reported. Distinct from widely used palladium-catalyzed formylation processes, this reaction proceeds by a two-step mechanistic sequence involving initial in situ generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN-mediated photoredox reaction. The formyl-radical equivalent then undergoes nickel-catalyzed substitution reactions with aryl halides and triflates and vinyl bromides to form the corresponding aldehyde products. Significantly, besides aryl bromides, less reactive aryl chlorides and triflates and vinyl halides serve as effective substrates for this process. Since the mild conditions involved in this reaction tolerate a plethora of functional groups, the process can be applied to the efficient preparation of diverse aromatic aldehydes.
- Huang, He,Li, Xiangmin,Yu, Chenguang,Zhang, Yueteng,Mariano, Patrick S.,Wang, Wei
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supporting information
p. 1500 - 1505
(2017/02/05)
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- Chemo- and Regioselective Organo-Photoredox Catalyzed Hydroformylation of Styrenes via a Radical Pathway
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An unprecedented, chemo- and regioselective, organo-photoredox catalyzed hydroformylation reaction of aryl olefins with diethoxyacetic acid as the formylation reagent is described. In contrast to traditional transition metal promoted ionic hydroformylation reactions, the new process follows a unique photoredox promoted, free radical pathway. In this process, a formyl radical equivalent, produced from diethoxacetic acid through a dye (4CzIPN) photocatalyzed, sequential oxidation-decarboxylation route, regio- and chemoselectively adds to a styrene substrate. Importantly, under the optimized reaction conditions the benzylic radical formed in this manner is reduced by SET from the anion radical of 4CzIPN to generate a benzylic anion. Finally, protonation produces the hydroformylation product. By using the new protocol, aldehydes can be generated regioselectively in up to 90% yield. A broad array of functional groups is tolerated in the process, which takes place under mild, metal-free conditions.
- Huang, He,Yu, Chenguang,Zhang, Yueteng,Zhang, Yongqiang,Mariano, Patrick S.,Wang, Wei
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supporting information
p. 9799 - 9802
(2017/08/02)
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- Difluoromethyl aldehyde hydrazone compound and preparation method thereof
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The invention relates to a difluoromethyl aldehyde hydrazone compound and a preparation method thereof. The method comprises the following steps: vacuumizing a reactor and then introducing argon for replacing, successively adding photosensitizer, alkali, additive, aldehyde derivative, hydrazine derivative, difluromethylation reagent and solvent, irradiating under visible light and reacting for 12-24h under normal temperature; after ending the reaction, removing the solvent through rotary evaporation, thereby acquiring a crude product; dissolving the crude product in dichloromethane and performing column chromatography on silica gel, thereby acquiring a difluoromethyl substituted difluoromethyl aldehyde hydrazone compound. According to the method provided by the invention, the clean sustainable visible light is taken as an energy source, the high-cost toxic ruthenium and iridium pyridine complex need not be used and the difluoromethylation of the aldehyde hydrazone compound can be conveniently realized through a simple operation step.
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Paragraph 0015; 0016
(2018/03/28)
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- Organic photoredox catalysis for the oxidation of silicates: Applications in radical synthesis and dual catalysis
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Metal free photooxidation of alkyl bis(catecholato)silicates with the organic dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN) allows the smooth formation of alkyl radicals. The latter can be efficiently engaged either with radical acceptors to provide homolytic addition products or in photoredox/nickel dual catalysis reactions to obtain cross-coupling products.
- Lévêque, Christophe,Chenneberg, Ludwig,Corcé, Vincent,Ollivier, Cyril,Fensterbank, Louis
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supporting information
p. 9877 - 9880
(2016/08/11)
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- Organic light-emitting device, and light-emitting material and compound used therefor
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An organic light-emitting device having a light-emitting layer containing a compound represented by the general formula below has a high light emission efficiency. In the general formula, at least one of R1 to R5 represents a cyano group, at least one of R1 to R5 represents a 9-carbazolyl group, a 1,2,3,4-tetrahydro-9-carbazolyl group, a 1-indolyl group or a diarylamino group, and the balance of R1 to R5 represents a hydrogen atom or a substituent.
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Page/Page column 126; 127
(2016/12/16)
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- Highly efficient organic light-emitting diodes from delayed fluorescence
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The inherent flexibility afforded by molecular design has accelerated the development of a wide variety of organic semiconductors over the past two decades. In particular, great advances have been made in the development of materials for organic light-emitting diodes (OLEDs), from early devices based on fluorescent molecules to those using phosphorescent molecules. In OLEDs, electrically injected charge carriers recombine to form singlet and triplet excitons in a 1:3 ratio; the use of phosphorescent metal-organic complexes exploits the normally non-radiative triplet excitons and so enhances the overall electroluminescence efficiency. Here we report a class of metal-free organic electroluminescent molecules in which the energy gap between the singlet and triplet excited states is minimized by design, thereby promoting highly efficient spin up-conversion from non-radiative triplet states to radiative singlet states while maintaining high radiative decay rates, of more than 10 6 decays per second. In other words, these molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels, leading to an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency, of more than 19 per cent, which is comparable to that achieved in high-efficiency phosphorescence-based OLEDs.
- Uoyama, Hiroki,Goushi, Kenichi,Shizu, Katsuyuki,Nomura, Hiroko,Adachi, Chihaya
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p. 234 - 238
(2013/02/23)
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