Photoinduced oxidative activation of electron-rich arenes: alkenylation with H<sub>2</sub> evolution under external oxidant-free conditions

Hu, Xia; Zhang, Guoting; Bu, Faxiang; Luo, Xu; Yi, Kebing; Zhang, Heng; Lei, Aiwen

doi:10.1039/c7sc04634k

Cited by 62 publications

(42 citation statements)

References 47 publications

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“…Two examples of electrocatalytic aromatic dehydrogenative Heck coupling of arenes were disclosed by Jutand and Lei groups 23,24 . Recently, Lei and coworkers also realized a direct dehydrogenative C-H alkenylation of electronrich arenes with styrene derivatives via a photo-induced electron transfer process 25 .…”

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confidence: 99%

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Zhu

2019

Nat Commun

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Alkenes are fundamental functionalities in nature and highly useful intermediates in organic synthesis, medicinal chemistry and material sciences. Transition-metal-catalyzed Heck couplings with organic halides as electrophiles have been established as a powerful protocol for the synthesis of this valuable building block. However, the requirement of organic halides and the generation of stoichiometric hazardous halide wastes may cause significant sustainable concerns. The halide-free oxidative Heck alkenylations involving organometallics or arenes as the coupling partners provide a facile and alternative pathway. Nonetheless, stoichiometric amounts of extra oxidant are essential in most cases. Herein, we present a direct dehydrogenative alkyl Heck-coupling reaction under oxidant-free conditions, liberating hydrogen, nitrogen and water as the side products. Excellent regioselectivity is achieved via neighboring oxygen atom coordination. Broad substrate scope, great functional group (ketone, ester, phenol, free amine, amide etc) tolerance and modification of pharmaceutical candidates and biological molecules exemplified its generality and practicability.

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confidence: 99%

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Zhu

2019

Nat Commun

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“…Regarding the cobalt‐catalyzed part of the mechanism, it is reported that step‐wise reduction of the Co(III) complex leads to Co(II) and Co(I) species ,,. We were able to visualize the formed Co(II) and Co(I) species by in‐situ UV/Vis measurements (Figure ).…”

Section: Resultsmentioning

confidence: 88%

Visible‐Light‐Mediated Photoredox‐Catalyzed N‐Arylation of NH‐Sulfoximines with Electron‐Rich Arenes

Wimmer

König

2018

Adv Synth Catal

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The direct C−H/N−H dehydrogenative cross‐coupling of NH‐sulfoximines with electron‐rich arenes was realized by oxidative visible‐light photoredox catalysis, applying 9‐mesityl‐10‐methylacridinium perchlorate as an organic photocatalyst. Sulfoximines display diverse desirable properties for medicinal chemistry and the pharmaceutical industry. However, their preparation is still challenging. Our reaction proceeds without sacrificial oxidant, at room temperature and is highly selective for the C−N bond forming reaction. The scope of the reaction includes mono‐ and multi‐alkylated and halogenated arenes, which are reacted with aromatic and aliphatic electron‐rich and electron‐poor NH‐sulfoximines, giving moderate to excellent yields of the N‐arylated sulfoximines. In addition, we successfully conducted the developed reaction on a gram scale (1.5 g). Mechanistic investigations show that both arene and NH‐sulfoximine interact with the excited‐state of the photocatalyst. We propose a radical‐based mechanism, where both the arene and the NH‐sulfoximine are photo‐oxidized to their respective radical intermediates. Radical‐radical cross‐coupling subsequently leads to the N‐arylated sulfoximine. Two electrons and two protons are released during the reaction and are subsequently converted into H2 by a proton‐reducing cobalt‐catalyst.

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“…White solid; mp 61–64 °C; 1 H NMR (CDCl 3 , 400 MHz) of trans-isomer: 7.45–7.43 (m, 3H), 7.26–7.23 (m, 2H), 6.87 (d, J = 8.4 Hz, 2H), 6.16 (s, 2H), 3.87 (s, 3H), 3.83 (s, 3H), 3.75 (s, 3H); 13 C NMR (CDCl 3 , 100 MHz): 160.23, 159.34, 158.37, 158.12, 132.55, 130.21, 129.51, 129.31, 127.30, 117.93, 114.23, 113.98, 113.06, 108.30, 90.82, 55.76, 55.55, 55.29, 55.28; IR (CHCl 3 ) ν max : 3437, 2912, 2847, 2312, 1724, 1600, 1501, 1422, 1300, 1265, 1112, 1013 cm –1 ; ESI-MS (−ve) m / z : 299.0 [M – H] − . 50…”

Section: Methodsmentioning

confidence: 99%

Nonantioxidant Tetramethoxystilbene Abrogates α-Synuclein-Induced Yeast Cell Death but Not That Triggered by the Bax or βA4 Peptide

et al. 2018

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The overexpression of α-synuclein (α-syn) and its aggregation is the hallmark of Parkinson’s disease. The α-syn aggregation results in the formation of Lewy bodies that causes neuronal cell death. Therefore, the small molecules that can protect neuronal cells from α-syn toxicity or inhibit the aggregation of α-syn could emerge as anti-Parkinson agents. Herein, a library of methoxy-stilbenes was screened for their ability to restore the cell growth from α-syn toxicity, using a yeast strain that stably expresses two copies of a chromosomally integrated human α-syn gene. Tetramethoxy-stilbene 4s , a nonantioxidant, was the most capable of restoring cell growth. It also rescues the more toxic cells that bear three copies of wild-type or A53T-mutant α-syn, from cell growth block. Its EC 50 values for growth restoration of the 2-copy wild-type and the 3-copy mutant α-syn strains are 0.95 and 0.35 μM, respectively. Stilbene 4s mitigates mitochondrial membrane potential loss, negates ROS production, and prevents nuclear DNA-fragmentation, all hallmarks of apoptosis. However, 4s does not rescue cells from the death-inducing effects of Bax and βA4, which suggest that 4s specifically inhibits α-syn-mediated toxicity in the yeast. Our results signify that simultaneous use of multiple yeast-cell-based screens can facilitate revelation of compounds that may have the potential for further investigation as anti-Parkinson’s agents.

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Photoinduced oxidative activation of electron-rich arenes: alkenylation with H₂ evolution under external oxidant-free conditions

Abstract: An external oxidant-free cross-coupling of electron-rich arenes and styrenes was enabled by a dual photoredox-cobaloxime catalytic system.

Cited by 62 publications

References 47 publications

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Visible‐Light‐Mediated Photoredox‐Catalyzed N‐Arylation of NH‐Sulfoximines with Electron‐Rich Arenes

Nonantioxidant Tetramethoxystilbene Abrogates α-Synuclein-Induced Yeast Cell Death but Not That Triggered by the Bax or βA4 Peptide

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Photoinduced oxidative activation of electron-rich arenes: alkenylation with H2 evolution under external oxidant-free conditions

Abstract: An external oxidant-free cross-coupling of electron-rich arenes and styrenes was enabled by a dual photoredox-cobaloxime catalytic system.

Cited by 62 publications

References 47 publications

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Visible‐Light‐Mediated Photoredox‐Catalyzed N‐Arylation of NH‐Sulfoximines with Electron‐Rich Arenes

Nonantioxidant Tetramethoxystilbene Abrogates α-Synuclein-Induced Yeast Cell Death but Not That Triggered by the Bax or βA4 Peptide

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Photoinduced oxidative activation of electron-rich arenes: alkenylation with H₂ evolution under external oxidant-free conditions