The past, present, and future of the Yang reaction

Chen, Chuo

doi:10.1039/c6ob01214k

Cited by 66 publications

(43 citation statements)

References 86 publications

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“…In the Norrish type II the exited ketone is converted to its 1,4‐biradical through an 1,5‐intramolecular hydrogen atom transfer (1,5‐HAT) (Scheme b). This intermediate can undergo many transformations, the elimination and the Yang cyclization being the most common . These two previously described transformations are exclusively for aliphatic ketones, while photoexcited bis‐arylketones, alkyl‐arylketones and 1,2‐diketones are also able to participate on intermolecular hydrogen abstractions, being normally reduced to the respective ketone or dimerized (pinacol coupling product) in the end of the reaction course (Scheme c) .…”

Section: Photochemistry Of Carbonyl Compounds: Fundamental Aspects Anmentioning

confidence: 99%

Photochemistry of Carbonyl Compounds: Application in Metal‐Free Reactions

et al. 2019

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Synthetic organic photochemistry is an efficient and environmentally friendly alternative to assemble biologically and chemically relevant scaffolds. The photon energy allows access to reactive intermediates by using a clean energy source under mild conditions. Moreover, sustainable synthesis can be achieved by using metal-free photochemistry. In this review, the photochemistry of carbonyl compounds and their application as reagents, catalysts or promoters of metal-free photochemical transformations are discussed. Fundamental aspects and reactivity of the carbonyl compounds are briefly presented in the introduction section, followed by recent applications of carbonyl compounds in photochemical reactions. The text is organized according to the role of the carbonyl compounds in the process. First, approaches in which carbonyl compounds are employed in stoichiometric or super-stoichiometric amounts (as reaction substrates or photoinitiators) are described. Thereafter, their application as photocatalysts and photosensitizers are discussed and mechanistic studies are comprehensively presented.

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Section: Photochemistry Of Carbonyl Compounds: Fundamental Aspects Anmentioning

confidence: 99%

Photochemistry of Carbonyl Compounds: Application in Metal‐Free Reactions

et al. 2019

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“…On the basis of the well-established reactivity of excited state diaryl ketone diradicals, which form ketyl radicals upon hydrogen atom abstraction (HAT) from both activated and unactivated C(sp 3 )–H bonds, 47 we envisioned a tricatalytic mechanism for net C–H arylation (Scheme 20). Early studies employing THF as H atom donor and solvent with one equivalent of benzophenone under standard coupling conditions afforded the desired product, albeit in moderate conversion.…”

Section: Photoredox/nickel Dual Catalysismentioning

confidence: 99%

Photoredox-Mediated Routes to Radicals: The Value of Catalytic Radical Generation in Synthetic Methods Development

et al. 2017

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Photoredox catalysis has experienced a revitalized interest from the synthesis community during the past decade. For example, photoredox/Ni dual catalysis protocols have been developed to overcome several inherent limitations of palladium-catalyzed cross-couplings by invoking a single-electron transmetalation pathway. This Perspective highlights advances made by our laboratory since the inception of the photoredox/Ni cross-coupling of benzyltrifluoroborates with aryl bromides. In addition to broadening the scope of trifluoroborate coupling partners, research using readily oxidized hypervalent silicates as radical precursors that demonstrate functional group compatibility is highlighted. The pursuit of electrophilic coupling partners beyond (hetero)aryl bromides has also led to the incorporation of several new classes of C(sp2)-hybridized substrates into light-mediated cross-coupling. Advances to expand the radical toolbox by utilizing feedstock chemicals (e.g., aldehydes) to access radicals that were previously inaccessible from trifluoroborates and silicates are also emphasized. Additionally, several organic photocatalysts have been investigated as replacements for their expensive iridium- and ruthenium-based counterparts. Lastly, the net C–H functionalization of the radical partner in an effort to improve atom economy is presented. An underlying theme in all of these studies is the value of generating radicals in a catalytic manner, rather than stoichiometrically.

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“…It has been documented that triplet carbonyls can abstract hydrogen atoms, especially those adjacent to heteroatoms (such as the O atom in ethers and alcohols), to produce the hydroxyalkyl radical. 44,45 Inspired by this and following our continued interest in photochemistry as a greener alternative to traditional transition-metal-catalyzed chemistry, [46][47][48][49][50][51][52][53][54] we anticipated that simply adding ketones into the reaction system would increase the generation rate of hydroxymethyl radical 15 (,CH 2 OH) because, under light irradiation, triplet ketone would be able to abstract the a-H of MeOH efficiently, 45 eventually leading to the efficient formation of direct-methylation product (16). Different from Jin and MacMillan's system 34 involving iridium photo-redox catalyst and odorous thiol organocatalyst, both of which are either expensive or not friendly to handle, we expected this system to avoid external catalysts and be driven solely by the solvent's intrinsic properties (Scheme 2B).…”

Section: Methodsmentioning

confidence: 99%

“…Recently, there has been a demand to synthesize tri-deuteromethylated heterocycles. 20,56 It was found that with this protocol, 2-methylquinoline could be tri-deuteromethylated with 76% yield (45), although other positions were also partially deuterated. Delightfully, purine-type substrate, as a key structural motif in many top-selling drugs, can also be methylated under the standard conditions (46).…”

Section: Scope Of the Investigationmentioning

confidence: 96%

Simple and Clean Photo-induced Methylation of Heteroarenes with MeOH

Liu

Yang

Zhou

et al. 2017

Chem

172

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A simple and efficient approach to the methylation of various heteroarenes, including six-and five-membered ones without transition metals, has been described at room temperature. This reaction is promoted by photo-energy with solvent MeOH as the methylation reagent and a dichloromethane co-solvent as the key promoter. The isotope-labeling studies indicate that the newly generated methyl group comprises two hydrogens from the methyl group and one hydrogen from the hydroxyl group of methanol.

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The past, present, and future of the Yang reaction

Cited by 66 publications

References 86 publications

Photochemistry of Carbonyl Compounds: Application in Metal‐Free Reactions

Photochemistry of Carbonyl Compounds: Application in Metal‐Free Reactions

Photoredox-Mediated Routes to Radicals: The Value of Catalytic Radical Generation in Synthetic Methods Development

Simple and Clean Photo-induced Methylation of Heteroarenes with MeOH

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