- Photoinduced Hydroarylation and Cyclization of Alkenes with Luminescent Platinum(II) Complexes
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Photoinduced hydroarylation of alkenes is an appealing synthetic strategy for arene functionalization. Herein, we demonstrated that aryl radicals generated from electron-deficient aryl chlorides/bromides could be trapped by an array of terminal/internal aryl alkenes in the presence of [Pt(O^N^C^N)] under visible-light (410 nm) irradiation, affording anti-Markovnikov hydroarylated compounds in up to 95 % yield. Besides, a protocol for [Pt(O^N^C^N)]-catalyzed intramolecular photocyclization of acrylanilides to give structurally diverse 3,4-dihydroquinolinones has been developed.
- Cheng, Hanchao,Lam, Tsz-Lung,Liu, Yungen,Tang, Zhou,Che, Chi-Ming
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supporting information
p. 1383 - 1389
(2020/11/30)
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- Electrochemistry enabled selective vicinal fluorosulfenylation and fluorosulfoxidation of alkenes
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Both sulfur and fluorine play important roles in organic synthesis, the life science, and materials science. The direct incorporation of these elements into organic scaffolds with precise control of the oxidation states of sulfur moieties is of great significance. Herein, we report the highly selective electrochemical vicinal fluorosulfenylation and fluorosulfoxidation reactions of alkenes, which were enabled by the unique ability of electrochemistry to dial in the potentials on demand. Preliminary mechanistic investigations revealed that the fluorosulfenylation reaction proceeded through a radical-polar crossover mechanism involving a key episulfonium ion intermediate. Subsequent electrochemical oxidation of fluorosulfides to fluorosulfoxides were readily achieved under a higher applied potential with the adventitious H2O in the reaction mixture.
- Jiang, Yimin,Shi, Zhaojiang,Wu, Jinnan,Wu, Shaofen,Ye, Keyin,Yu, Yi,Yuan, Yaofeng
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supporting information
(2021/11/17)
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- Deaminative carbonylative coupling of alkylamines with styrenes under transition-metal-free conditions
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A transition-metal-free deaminative carbonylation of alkylamines with styrenes has been developed. The reaction shows good functional group compatibility and various α,β-unsaturated ketones were obtained in moderate to good yields. The alkyl radical generated from Katritzky salts via base-promoted C-N bond cleavage is one of the key intermediates in this reaction. This journal is
- Zhao, Fengqian,Li, Chong-Liang,Wu, Xiao-Feng
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supporting information
p. 9182 - 9185
(2020/08/26)
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- Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’-Reductases with Photoredox Catalysts
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Flavin-dependent ‘ene’-reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long-lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models.
- Biegasiewicz, Kyle F.,Black, Michael J.,Chung, Megan M.,Hyster, Todd K.,Meichan, Andrew J.,Nakano, Yuji,Sandoval, Braddock A.,Zhu, Tianyu
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supporting information
p. 10484 - 10488
(2020/04/29)
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- Bisoxazoline-pincer ligated cobalt-catalyzed hydrogenation of alkenes
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The efficient and atom economical hydrogenation of alkenes using a novel bisoxazoline ligated cobalt complex has been developed. The hydrogenation of a variety of alkenes containing electron neutral and electron-donating groups proceeds in high yield, whi
- Ritz, Mikhaila D.,Parsons, Astrid M.,Palermo, Philip N.,Jones, William D.
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supporting information
(2020/02/13)
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- Radical C?H Bond Trifluoromethylation of Alkenes by High-Valent Copper(III) Trifluoromethyl Compounds
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A general and selective method is developed that allows direct vinylic C?H bond trifluoromethylation of 1,1-diarylalkenes by a high-valent copper(III) trifluoromethyl complex, producing biologically active trifluoromethylated alkenes (as well as trifluoro
- Zhang, Hao-Ran,Xiao, Chang,Zhang, Song-Lin,Zhang, Xiaoming
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supporting information
p. 5305 - 5310
(2019/11/22)
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- A Palladium NNC-Pincer Complex as an Efficient Catalyst Precursor for the Mizoroki?Heck Reaction
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The Mizoroki?Heck reaction of aryl halides (iodides, bromides, or chlorides) with activated alkenes in the presence of a palladium NNC-pincer complex at ppb to ppm loadings gave the corresponding internal alkenes in excellent yields. The total turnover number and turnover frequency reached up to 8.70×108 and 1.21×107 h?1 (3.36×103 s?1), respectively. The catalyst was applied in a ten-gram-scale synthesis of the UV-B sunscreen agent octinoxate (2-ethylhexyl 4-methoxycinnamate). Reaction-rate analyses, transmission electron microscopic examination of the reaction mixture, and poisoning tests suggested that a monomeric palladium species is the catalytically active species in the catalytic cycle. (Figure presented.).
- Hamasaka, Go,Ichii, Shun,Uozumi, Yasuhiro
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supporting information
p. 1833 - 1840
(2018/04/05)
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- Electrochemically Enabled Carbohydroxylation of Alkenes with H2O and Organotrifluoroborates
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Unprecedented hydroxy-alkynylation and -alkenylation reactions of arylalkenes have been developed through electrochemically enabled addition of an organotrifluoroborate reagent and H2O across the double bond of the alkene. The use of electrochemistry to promote these oxidative alkene 1,2-difunctionalization reactions not only obviates the need for transition-metal catalysts and oxidizing reagents but also ensures high regio- and chemoselectivity to afford homopropargylic or homoallylic alcohols. The possibility of extending the electrochemical alkene difunctionalization strategy to other alkene carbo-heterofunctionalization reactions has been demonstrated.
- Xiong, Peng,Long, Hao,Song, Jinshuai,Wang, Yaohui,Li, Jian-Feng,Xu, Hai-Chao
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supporting information
p. 16387 - 16391
(2018/11/23)
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- Direct C-H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis
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Background: Trifluoromethylated alkene scaffolds are known as useful structural motifs in pharmaceuticals and agrochemicals as well as functional organic materials. But reported synthetic methods usually require multiple synthetic steps and/or exhibit lim
- Tomita, Ren,Yasu, Yusuke,Koike, Takashi,Akita, Munetaka
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supporting information
p. 1099 - 1106
(2014/06/09)
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- Recyclable ligand-free mesoporous heterogeneous Pd catalysts for Heck coupling
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Ligand-free Pd-MCM41 catalysts are highly active in the Heck coupling of bromoarenes including deactivated bromo derivatives to give coupled products in high yields with high selectivities without the need to exclude air or moisture. The catalyst samples exhibit unprecedented stability among heterogeneous catalysts and can be reused at least 20 times to achieve complete conversion without any additional activation treatment.
- Papp, Attila,Galbács, Gábor,Molnár, árpád
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p. 7725 - 7728
(2007/10/03)
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- Synthesis of 1,1-diarylethylenes from an α-stannyl β-silylstyrene
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The synthesis of a family of 1,1-diarylethylenes from an α-stannyl β-silylstyrene through a combination of a Stille coupling and a protodesilylation reaction is described. This approach avoids the problematic cine-substitution, which is a well documented side reaction during the palladium-assisted elaboration of α-substituted vinylstannanes to 1,1-disubstituted ethylenes.
- Belema, Makonen,Nguyen, Van N.,Zusi, F. Christopher
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p. 1693 - 1697
(2007/10/03)
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- Pd-catalyzed decarbonylative olefination of aryl esters: Towards a waste-free Heck reaction
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Easy and clean: A palladium (0)-catalyzed decarbonylative Heck olefination of activated esters of aryl, heteroaryl, and vinyl carboxylic acids opens up an opportunity for a novel waste-free Heck olefination process (see scheme).
- Goossen, Lukas J.,Paetzold
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p. 1237 - 1241
(2007/10/03)
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- On the stille vinylation reactions with α-styryltrimethyltin
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Stille vinylation reactions involving α-styryltrimethyltin 3b and a series of chloro- or bromo-pyridine derivatives are described. In contrast to the rare cine selectivity observed with iodobenzene 10a or 3-iodotoluene 10b, reactions between vinyltin 3b and a series of 2-halopyridine derivatives 15(a-d) yield 1,1-disubstituted ipso-coupled olefins 16(a-d) as the predominant products.
- Chen, Shu-Hui
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p. 4741 - 4744
(2007/10/03)
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- Kinetic Energy Release and Position of Transition State during Intramolecular Aromatic Substitution in Ionized 1-Phenyl-1-(2-pyridyl)ethylenes
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The loss of substituents (X = H, CH3, Cl, Br, I) from the molecular ions of ortho-substituted 1-phenyl-1-(2-pyridyl)ethylenes 1a-f and of the isomeric 1-phenyl-1-(3-pyridyl)- and 1-phenyl-1-(4-pyridyl)ethylenes 2 and 3 has been investigated.Cyclic fragment ions a are formed from the ortho-substituted 1-phenyl-1-(2-pyridyl)ethylene molecular ions by an intramolecular aromatic substitution reaction.The energetic requirements of this reaction have been studied in dependence from the dissociation energy of the C-X bond by measurements of the ionization energies, appearance energies, and kinetic energies released during the reaction.The activation energy εh of the process varies only slightly with the dissociation energy of the C-X bond cleaved during the reaction, whereas the entalpy of reaction changes from positive (endothermic) to very negative (exothermic) values in the reaction series 1a-f.Consequently the reverse activation energy εr ranges from small to very large values in this series.This trend in εr is not followed by the kinetic-energy release.A large kinetic-energy release and energy partitioning quotient q = 0.7 - 1.0 is only observed for endothermic or thermoneutral processes, while a small kinetic-energy release and q ca. 0.2 is associated with exothermic reactions in spite of a large εr.This behavior has been correlated to the position Xo* of the transition state on the reaction coordinate according to Miller's quantification of the Hammond postulate.The release of εr as kinetic energy is only observed for reactions with "symmetrical" or "late" transition states (Xo* > 0.4) while most of εr remains as internal energy in the products of reactions with "early" transition states (Xo* 0.4).
- Schubert, Ralf,Gruetzmacher, Hans-Friedrich
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p. 5323 - 5328
(2007/10/02)
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