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Версия для печати | Главная > Центр > Научные советы > Научный совет по катализу > ... > 2021 год > № 99

№ 99

 

Содержание

  • Валерий Иванович БУХТИЯРОВ – к 60-летнему юбилею
  • Зинфер Ришатович Исмагилов – лауреат премии
    «Глобальная энергия-2021»
  • VI Семинар памяти профессора Ю.И. Ермакова
    «Гомогенные и закрепленные металлокомплексные катализаторы
    для процессов олимеризации и нефтехимии»
  • Заседание Некоммерческого партнерства
    “Национальное каталитическое общество”
  • Круглый стол «Исследовательская карьера: от молодого ученого до лидера проекта» на IV Российском конгрессе «Роскатализ»
  • За рубежом
  • Приглашения на конференции



Валерий Иванович Бухтияров - к 60-летнему юбилею

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Зинфер Ришатович Исмагилов – лауреат премии «Глобальная энергия-2021»

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VI Семинар памяти профессора Ю.И. Ермакова

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Заседание Некоммерческого партнерства “Национальное каталитическое общество” на IV Российском конгрессе «Роскатализ»

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Круглый стол «Исследовательская карьера: от молодого ученого до лидера проекта» на IV Российском конгрессе «Роскатализ»

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За рубежом

Glass catalysis shatters material’s inert reputation

The surface of glass can act as a strong base to catalyze reactions and degrade certain reagents

Beakers, flasks, petri dishes—glassware is a hallmark of chemistry labs. Though commonly thought of as inert, glass containers are known to affect certain chemical reactions, but researchers have not understood exactly how or to what extent. Now, a team reports that glass beads can catalyze many base-catalyzed reactions, suggesting that glass could be used as a green catalyst in place of toxic or expensive chemicals (Chem. Science, 2021, DOI: 10.1039/d1sc02708e)

Late last year, Yangjie Li of Graham Cooks’s lab at Purdue University published work based on an accidental discovery that an amine transfer reaction proceeded faster in glassware than in plastic, and that adding glass beads accelerated reactions even further (Angew. Chem., Int. Ed. 2020, DOI: 10.1002/anie.202014613). Li wanted to find out more.

Li and colleagues tested thousands of reaction conditions and dozens of reactions to see how the presence of glass microspheres affected various reaction types. “We found that there are so many base-catalyzed reactions that can be catalyzed by just adding these glass particles in the solution”—as opposed to the expensive, caustic basic chemicals typically used for these kinds of reactions, she says. Glass beads accelerated elim-ination, solvolysis, condensation, and oxidation reactions 30- to 2,000-fold.

The surface of glass is covered with dissociable silanol groups, giving it a negative charge when in contact with solution. The researchers determined that this allows glass to act as a strong base while producing nucleophilic solvent anions that catalyze reactions.

“The second very important part of [the study] is that we found that glass can degrade biomolecules such as lipids,” Li says. “So it could be a huge impact in bioanalytical work and in clinical settings.”

Cooks says that for standard concentrated solutions stored in a glass container, “there’s no problem at all” because “99.9% of the material will not make it to the surface.” But he adds that for specialty low-concentration ingredients or analytical tests at low concentrations, “we found significant loss of the material.”

“I think it is an outstanding new direction,” says Richard Zare, a physical and analytical chemist at Stanford University who was not part of the study. Zare is interested in how this can be scaled up as a practical means of making new chemicals.

 

 

Core-shell catalysts made of two metals combine high activity with high selectivity

Careful preparation avoids catalytic trade-offs


These catalysts consist of a gold core, a palladium shell ranging in thickness from 

one atom (left) to six (right), and a protective silica layer.

By carefully controlling the structure and composition of bimetallic nanoparticles, researchers have come up with a high-performance model catalyst that blends the best features of each metal. The advance could lead to commercial catalysts that cut manufacturing costs and reduce waste. Heterogeneous catalysts, which generally contain one type of metal, drive most industrial-scale chemical processes. Blending two metals can increase catalysts’ capabilities, for example, by mediating separate steps of a reaction. But most methods for preparing mixed-metal catalysts lead to particles with variations in composition, size, and shape. The lack of control often causes a trade-off between catalytic activity and chemical selectivity. A team of researchers led by Jessi E. S. van der Hoeven, Alfons van Blaaderen, and Petra E. de Jongh of Utrecht University has now shown how to combine metals to make catalysts that are active and selective. The team made a series of uniform nanorods, each with a gold core and a palladium shell of predetermined thickness. The researchers capped the rods with porous silica and tested them catalytically in the selective hydrogenation of 1,3-butadiene, a process used for purifying propene feedstocks. The core-shell catalysts were all highly selective, a trademark of gold, yet they were up to 50 times as active as catalysts made of a single metal or random mixtures of the metals (Nat. Mater. 2021, DOI: 10.1038/s41563-021-00996-3).

 

 

Copper catalysts team up for chiral amide synthesis

Blue light powers a radical route to ubiquitous functional group


A pair of copper catalysts can create chiral amides in a new, light-driven process, offering a useful alternative to the standard method for making these staples of medicinal chemistry (Nature 2021, DOI: 10.1038/s41586-021-03730-w).

“Amides are ubiquitous functional groups in bioactive molecules, such as peptides,” says Gregory C. Fu at the California Institute of Technology, who coled the work.

The conventional route to amides involves reacting an amine with a carboxylic acid derivative. So if chemists want to selectively create just one of the mirror-image enantiomers of a chiral amide, they generally start with a single enantiomer of the amine. That sequence typically involves at least two steps—one to control the stereochemistry of the amine precursor and a second to form the amide.

In contrast, the Caltech team’s method achieves this in a single step without using single-enantiomer precursors by controlling the stereochemistry of the amide as it forms. “We’re hoping this leads to a more efficient process,” Fu says.

The reaction relies on two different copper catalysts and combines an amide with an alkyl bromide to form a chiral secondary amide—where the nitrogen atom is bonded to a hydrogen and two carbons, one of which is chiral.

The first catalyst is a copper (I) bisphosphine phenoxide complex. Once activated by blue light, it removes bromine from the alkyl bromide to release an alkyl radical. Meanwhile, the second catalyst, a chiral copper (II) diamine complex, binds to the primary amide and unites it with the alkyl radical. This stereoselectively forms a C–N bond, replacing one of the amide’s hydrogen atoms with the alkyl group to produce a secondary amide. As these two catalytic cycles keep turning, the copper complexes alternate between +1 and +2 oxidation states.

The reaction is tolerant to air or moisture and works for a diverse array of primary amides. It is also compatible with various functional groups in the alkyl bromide precursor. Amide yields range from 53%–95%, with a single enantiomer making up at least 95% of the product. “I find it quite remarkable that Caiyou Chen, the postdoc who’s done this work, has been able to showcase efficacy over such a broad range of directing groups, with such high yields and enantioselectivity,” says Caltech’s Jonas C. Peters, who coled the work with Fu.

“I think this paper is really amazing,” says Nicolas Blanchard, a French National Center for Scientific Research research director at the University of Strasbourg, who was not involved in the research. “With three simple ligands, they’ve been able to solve something that was really unattainable, in my view.”

Blanchard’s own research involves copper-catalyzed reactions for organic synthesis, and he says the new amide-forming reaction highlights growing interest in the metal. “Copper is used more and more, especially in photocatalyzed reactions,” he says. “These authors were pioneers in that regard.”

Chemical & Engineering News


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