- 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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p. 21418 - 21425
(2021/08/25)
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- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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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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- Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with Organoboron Compounds
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A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni?H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C?H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.
- Xiao, Li-Jun,Cheng, Lei,Feng, Wei-Min,Li, Mao-Lin,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 461 - 464
(2018/02/21)
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- Benzylation of arenes with benzyl halides synergistically promoted by in situ generated superacid boron trifluoride monohydrate and tetrahaloboric acid
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To examine the assembly methodology of diarylmethanes, a benzylation of (hetero)arenes with benzyl halides has been developed and various diarylmethanes were furnished with yields of up to 98% and regioselectivities of up to >99%. The complexation of the by-product halogen hydride with BF3·OEt2 generated the Bronsted acid BF3·HX (HBF3X, X=Cl or Br) in situ to synergistically promote the benzylation.
- Huang, Ruofeng,Zhang, Xiaohui,Pan, Jing,Li, Jiaqiang,Shen, Hang,Ling, Xuege,Xiong, Yan
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supporting information
p. 1540 - 1546
(2015/03/04)
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- Aldimine-directed branched-selective hydroarylation of styrenes
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Branching out: A simple and inexpensive cobalt/triarylphosphine catalyst promotes aldimine-directed hydroarylation of styrene with high branched regioselectivity to afford 1,1-diarylethane derivatives in good yields under mild reaction conditions. The ortho-formyl group in the hydroarylation products is amenable to dehydrative cyclization, to give fused polycyclic aromatic hydrocarbons, as well as decarbonylative removal. Copyright
- Lee, Pin-Sheng,Yoshikai, Naohiko
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p. 1240 - 1244
(2013/03/13)
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- Selective one-pot synthesis of various phenols from diarylethanes
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Various substituted phenols were selectively synthesized by a one-pot reaction through the NHPI-catalyzed aerobic oxidation of 1,1-diarylethanes followed by treatment with dilute sulfuric acid. The Royal Society of Chemistry.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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supporting information; experimental part
p. 3417 - 3419
(2009/02/05)
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- An efficient and general iron-catalyzed arylation of benzyl alcohols and benzyl carboxylates
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(Chemical Equation Presented) Green grow the diarylmethanes: Substituted arenes and heteroarenes can be easily benzylated in the presence of inexpensive and relatively nontoxic metal salts such as FeCl3 (see scheme). This arylation method with benzyl alcohols is a state-of-the-art green route to diarylmethanes as water is the only by-product.
- Iovel, Irina,Mertins, Kristin,Kischel, Jette,Zapf, Alexander,Beller, Matthias
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p. 3913 - 3917
(2007/10/03)
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- Novel reductive Friedel-Crafts alkylation of aromatics catalyzed by indium compounds: Chemoselective utilization of carbonyl moieties as alkylating reagents
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Reductive Friedel-Crafts alkylation of aromatics with ketones or aldehydes was characteristically catalyzed by indium compounds in preference to general catalysts like AlCl3 and BF3, where hydrosilanes would play an important role both as a hydride donor and as a co-catalyst. Chemoselective utilization of ketone moieties as alkylating reagents took place even in the presence of halogen, ester or ether moieties which are very susceptible under traditional Friedel-Crafts conditions. Discussion on a plausible intermediate was carried out by some controlled experiments.
- Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
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p. 1017 - 1026
(2007/10/03)
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- Indium trichloride catalyzed reductive Friedel-Crafts alkylation of aromatics using carbonyl compounds
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Reductive Friedel-Crafts alkylation of aromatics with aldehydes or ketones using chlorodimethylsilane as a hydride source was effectively promoted by a catalytic amount of indium trichloride, whereas a popular type of Friedel-Crafts catalysts showed less effect.
- Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
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p. 6291 - 6294
(2007/10/03)
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- PREPARATION OF SOME TRIMETHYL- AND METHYLETHYLBIPHENYLS AND REACTIVITY OF AROMATIC HYDROCARBONS IN THE GOMBERG REACTION
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Trimethyl- and methylethylbiphenyls with the alkyl groups in the both phenyl rings have been prepared by the Gomberg reaction and identified by the capillary gas-liquid chromatography.Depending on choice of the aromatic hydrocarbon either individual isomers or their mixtures (three at the most) have been obtained which were contaminated with compounds of diarylmethane type in many cases.The methylethylbiphenyls have only been prepared as mixtures contaminated with diarylmethanes.These side products have been prepared by independent syntheses.A method has been developed for isolation and separation of mixtures of trimethyl- and methylethylbiphenyls from the reaction products containing tarry products.The method is suitable for preparation of small amounts of some analytical standards.The HMO method has been used for calculation of values of the radical superdelocalizabilities at individual centres in the molecules of o-, m- and p-xylene, toluene and ethylbenzene, and these values have been compared with composition of the Gomberg reaction products from these hydrocarbons.The competitive technique has been used for comparison of the reactivities of the mentioned aromatic substrates in the Gomberg reactions.
- Novrocik, Jan,Novrocikova, Marta,Titz, Milos
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p. 3140 - 3149
(2007/10/02)
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