Carboxylate-Assisted Ruthenium-Catalyzed Alkyne Annulations by C–H/Het–H Bond Functionalizations

Accounts of Chemical Research, Год журнала: 2013, Номер 47(2), С. 281 - 295

Опубликована: Фев. 4, 2013

To improve the atom- and step-economy of organic syntheses, researchers would like to capitalize upon chemistry otherwise inert carbon–hydrogen (C–H) bonds. During past decade, remarkable progress in organometallic has set stage for development increasingly viable metal catalysts C–H bond activation reactions. Among these methods, oxidative functionalizations are particularly attractive because they avoid use prefunctionalized starting materials. For example, annulations that involve sequential heteroatom–H cleavages allow modular assembly regioselectively decorated heterocycles. These structures serve as key scaffolds natural products, functional materials, crop protecting agents, drugs. While other have devised rhodium or palladium complexes alkyne annulations, my laboratory focused on application significantly less expensive, yet highly selective ruthenium complexes.This Account summarizes evolution versatile ruthenium(II) alkynes via C–H/N–H, C–H/O–H, C–H/N–O cleavages. achieve functionalizations, we needed understand detailed mechanism crucial metalation with importance carboxylate assistance this process. As a consequence, our recent efforts resulted widely applicable methods preparation differently arenes heteroarenes, providing access among others isoquinolones, 2-pyridones, isoquinolines, indoles, pyrroles, α-pyrones. Most reactions used Cu(OAc)2·H2O, which not only acted oxidant but also served essential source acetate carboxylate-assisted ruthenation manifold. Notably, ruthenium(II)-catalyzed occurred under an ambient atmosphere air cocatalytic amounts Cu(OAc)2·H2O. Moreover, substrates displaying N–O bonds "internal oxidants" syntheses isoquinolones isoquinolines. Detailed experimental mechanistic studies provided strong support catalytic cycle relies initial ruthenation, followed by coordinative insertion alkyne, reductive elimination, reoxidation thus formed ruthenium(0) complex.

Язык: Английский

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Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen

Science, Год журнала: 2014, Номер 344(6184), С. 616 - 619

Опубликована: Май 8, 2014

The efficient use of natural gas will require catalysts that can activate the first C-H bond methane while suppressing complete dehydrogenation and avoiding overoxidation. We report single iron sites embedded in a silica matrix enable direct, nonoxidative conversion methane, exclusively to ethylene aromatics. reaction is initiated by catalytic generation methyl radicals, followed series gas-phase reactions. absence adjacent prevents C-C coupling, further oligomerization, hence, coke deposition. At 1363 kelvin, reached maximum at 48.1% selectivity peaked 48.4%, whereas total hydrocarbon exceeded 99%, representing an atom-economical transformation process methane. lattice-confined delivered stable performance, with no deactivation observed during 60-hour test.

Язык: Английский

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Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects

Chemical Reviews, Год журнала: 2017, Номер 117(13), С. 8497 - 8520

Опубликована: Май 5, 2017

The quest for an efficient process to convert methane efficiently fuels and high value-added chemicals such as olefins aromatics is motivated by their increasing demands recently discovered large reserves resources of methane. Direct conversion these can be realized either oxidatively via oxidative coupling (OCM) or nonoxidatively dehydroaromatization (MDA), which have been under intensive investigation decades. While industrial applications are still limited low yield (selectivity) stability issues, innovations in new catalysts concepts needed. newly emerging strategy using iron single sites catalyze olefins, aromatics, hydrogen (MTOAH) attracted much attention when it was reported. Because the challenge lies controlled dehydrogenation highly stable CH4 selective C–C coupling, we focus mainly on fundamentals C–H activation analyze reaction pathways toward routes OCM, MDA, MTOAH. With this, intend provide some insights into mechanisms implications future development direct chemicals.

Язык: Английский

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Green Carbon Science: Scientific Basis for Integrating Carbon Resource Processing, Utilization, and Recycling

Angewandte Chemie International Edition, Год журнала: 2013, Номер 52(37), С. 9620 - 9633

Опубликована: Июль 26, 2013

How green was my valley: Green carbon science focuses on the transformations of carbon-containing compounds in entire cycle. The ultimate aim is to use resources efficiently and minimize net CO2 emission. This holistic view also has ramifications for related fields including petroleum refining production liquid fuels chemicals from coal, methane, CO2, biomass.

Язык: Английский

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Selective anaerobic oxidation of methane enables direct synthesis of methanol

Science, Год журнала: 2017, Номер 356(6337), С. 523 - 527

Опубликована: Май 4, 2017

Direct functionalization of methane in natural gas remains a key challenge. We present direct stepwise method for converting into methanol with high selectivity (~97%) over copper-containing zeolite, based on partial oxidation water. The activation helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars and then water 473 K, consistently produced 0.204 mole CH3OH per copper zeolite. Isotopic labeling confirmed as the source oxygen regenerate zeolite active centers renders desorption energetically favorable. On basis situ x-ray absorption spectroscopy, infrared density functional theory calculations, we propose mechanism involving CuII oxide centers, CuI reoxidation concurrent formation hydrogen.

Язык: Английский

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Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry

Chemical Society Reviews, Год журнала: 2014, Номер 43(10), С. 3480 - 3480

Опубликована: Янв. 1, 2014

Oxidation catalysis not only plays a crucial role in the current chemical industry for production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to establishment novel green sustainable processes. This review is devoted dealing with selective oxidation reactions, which are important from viewpoint chemistry still remain challenging. Actually, some well-known highly challenging reactions involve methane by oxygen. On other hand aerobic alcohols liquid phase preferential carbon monoxide hydrogen, have attracted much attention recent years because their high significance or energy chemistry. article summarizes advances development new catalytic materials systems these reactions. A deep scientific understanding mechanisms, active species structures discussed. Furthermore, connections among distinct highlighted, gain insight breakthrough rational design efficient

Язык: Английский

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Catalysis by clusters with precise numbers of atoms

Nature Nanotechnology, Год журнала: 2015, Номер 10(7), С. 577 - 588

Опубликована: Июль 1, 2015

Язык: Английский

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Methane Activation by Heterogeneous Catalysis

Catalysis Letters, Год журнала: 2014, Номер 145(1), С. 23 - 39

Опубликована: Ноя. 20, 2014

Язык: Английский

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Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C–H activation

Nature Chemistry, Год журнала: 2018, Номер 10(3), С. 325 - 332

Опубликована: Янв. 8, 2018

Язык: Английский

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Understanding trends in C–H bond activation in heterogeneous catalysis

Nature Materials, Год журнала: 2016, Номер 16(2), С. 225 - 229

Опубликована: Окт. 10, 2016

Язык: Английский

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