Mild metal-catalyzed C–H activation: examples and concepts

Chemical Society Reviews, Journal Year: 2016, Volume and Issue: 45(10), P. 2900 - 2936

Published: Jan. 1, 2016

C–H Activation reactions that proceed under mild conditions are more attractive for applications in complex molecule synthesis. Mild transformations reported since 2011 reviewed and the different concepts strategies have enabled their mildness discussed.

Language: Английский

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Transition-Metal-Catalyzed Cross-Couplings through Carbene Migratory Insertion

Chemical Reviews, Journal Year: 2017, Volume and Issue: 117(23), P. 13810 - 13889

Published: Nov. 1, 2017

Transition-metal-catalyzed cross-coupling reactions have been well-established as indispensable tools in modern organic synthesis. One of the major research goals area is expanding scope coupling partners. In past decade, diazo compounds (or their precursors N-tosylhydrazones) emerged nucleophilic partners C-C single bond or C═C double formations transition-metal-catalyzed reactions. This type reaction involves following general steps. First, organometallic species generated by various processes, including oxidative addition, transmetalation, cyclization, cleavage, and C-H activation. Subsequently, reacts with substrate to generate metal carbene intermediate, which undergoes rapid migratory insertion form a bond. The new from may undergo transformations. carbene-based has proven be general: transition metals Pd, Cu, Rh, Ni, Co, Ir are effective catalysts; also extended substrates other than compounds; cascade processes devised based on insertion. review will summarize achievements made this field since 2001.

Language: Английский

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Catalytic Enantioselective Transformations Involving C–H Bond Cleavage by Transition-Metal Complexes

Chemical Reviews, Journal Year: 2017, Volume and Issue: 117(13), P. 8908 - 8976

Published: Feb. 17, 2017

The development of new methods for the direct functionalization unactivated C-H bonds is ushering in a paradigm shift field retrosynthetic analysis. In particular, catalytic enantioselective represents highly atom- and step-economic approach toward generation structural complexity. However, as result their ubiquity low reactivity, controlling both chemo- stereoselectivity such processes constitutes significant challenge. Herein we comprehensively review all asymmetric transition-metal-catalyzed methodologies that are believed to proceed via an inner-sphere-type mechanism, with emphasis on nature stereochemistry generation. Our analysis serves document considerable rapid progress within field, while also highlighting limitations current methods.

Language: Английский

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Chiral Cyclopentadienyls: Enabling Ligands for Asymmetric Rh(III)-Catalyzed C–H Functionalizations

Accounts of Chemical Research, Journal Year: 2015, Volume and Issue: 48(5), P. 1308 - 1318

Published: April 17, 2015

ConspectusTransition-metal catalyzed C–H functionalizations became a complementary and efficient bond-forming strategy over the past decade. In this respect, Cp*Rh(III) complexes have emerged as powerful catalysts for broad spectrum of reactions giving access to synthetically versatile building blocks. Despite their high potential, corresponding catalytic enantioselective transformations largely lag behind. The targeted require all remaining three coordination sites central rhodium atom catalyst. consequence, chiral information on competent catalyst can only by stored in cyclopentadienyl unit. lack suitable enabling (Cpx) ligands is key hurdle preventing development such asymmetric versions. an set Cpx useable with variety different transition-metals unlock substantial application potential. This Account provides description our developments two classes C2-symmetric derivatives. We introduced side- back-wall concept enforce chirality transfer onto metal atom. first generation consists fused cyclohexane unit having pseudo axial methyl groups selectors rigidifying acetal moiety. second ligand derives from atrop-chiral biaryl-backbone which possesses adjustable substituents at its 3,3′-positions. Both families be modulated respective steric bulk adjust specific needs application. cyclopentadienes metalated under standard conditions. rhodium(I) ethylene are relatively air moisture represent storable stable precatalysts Rh(III)-catalyzed functionalizations. These then conveniently oxidized situ dibenzoyl peroxide give reactive CpxRh(III)(OBz)2 species. For instance, used directed activations aryl hydroxamates subsequent trapping olefins, providing dihydroisoquinolones very enantioselectivities. addition, we established highly selective intramolecular tethered higher substituted alkenes dihydrobenzofurans quaternary stereogenic centers. Concerning intermolecular reactions, allene coupling partners allow hydroarylation yielding allylated compounds. A process cyclometalated intermediate diazo reactants enables construction isoindolinones. Moreover, atropchiral biaryl motives using dehydrogenative Heck-type reaction. flexibly described showcasing applicability Rh(III) functionalization reactions. derivatives hold promise steering further catalysis.

Language: Английский

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A Simple and Versatile Amide Directing Group for C−H Functionalizations

Angewandte Chemie International Edition, Journal Year: 2016, Volume and Issue: 55(36), P. 10578 - 10599

Published: Aug. 1, 2016

Abstract Achieving selective C−H activation at a single and strategic site in the presence of multiple bonds can provide powerful generally useful retrosynthetic disconnection. In this context, directing group serves as compass to guide transition metal by using distance geometry recognition parameters distinguish between proximal distal bonds. However, installation removal groups is practical drawback. To improve utility approach, one seek solutions three directions: 1) Simplifying group, 2) common functional or protecting groups, 3) attaching substrates via transient covalent bond render catalytic. This Review describes rational development an extremely simple yet broadly applicable for Pd II , Rh III Ru catalysts, namely N‐methoxy amide (CONHOMe) moiety. Through collective efforts community, wide range transformations type have been developed.

Language: Английский

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Transition metal-catalyzed C–H functionalization of N-oxyenamine internal oxidants

Chemical Society Reviews, Journal Year: 2014, Volume and Issue: 44(5), P. 1155 - 1171

Published: Nov. 24, 2014

The N-oxyenamine internal oxidant gives more chance to investigate the C–H bond activation under mild reaction conditions.

Language: Английский

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Metal‐Catalyzed Annulations through Activation and Cleavage of C−H Bonds

Angewandte Chemie International Edition, Journal Year: 2016, Volume and Issue: 55(37), P. 11000 - 11019

Published: June 22, 2016

The exponential increase in the number of catalytic transformations that involve a metal-promoted activation hitherto considered inert C-H bonds is promoting fundamental change field synthetic chemistry. Although most reactions involving activations consist simple functionalizations or additions, recent years have witnessed an upsurge related can be formally as cycloaddition processes. These are particularly appealing from perspective because they allow conversion readily available substrates into highly valuable cyclic products rapid and sustainable manner. In many cases, these annulations formation metallacyclic intermediates resemble those proposed for standard metal-catalyzed cycloadditions unsaturated precursors.

Language: Английский

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Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes

Journal of the American Chemical Society, Journal Year: 2016, Volume and Issue: 138(16), P. 5242 - 5245

Published: April 12, 2016

The vastly increasing application of chiral Cp ligands in asymmetric catalysis results growing demand for novel ligands. Herein, we report a new class based on 1,1′-spirobiindane, privileged scaffold and catalysts. corresponding Rh complexes are shown to be excellent catalysts oxidative coupling reactions, providing axially biaryls 19–97% yields with up 98:2 er.

Language: Английский

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Rhodium-Catalyzed C–H Activation of Phenacyl Ammonium Salts Assisted by an Oxidizing C–N Bond: A Combination of Experimental and Theoretical Studies

Journal of the American Chemical Society, Journal Year: 2015, Volume and Issue: 137(4), P. 1623 - 1631

Published: Jan. 8, 2015

Rh(III)-catalyzed C–H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite success, these coupling systems are currently limited cleavage N–O or N–N bond. Cleavage C–N bond, which allows complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with bond have been designed as substrates under redox-neutral conditions. The α-diazo esters afforded benzocyclopentanones, unactivated alkenes such styrenes aliphatic olefins gave ortho-olefinated acetophenoes. both reactions proceeded broad scope, high efficiency, functional tolerance. Moreover, efficient one-pot diazo realized starting from α-bromoacetophenones triethylamine. reaction mechanism studied combination experimental theoretical methods. particular, three distinct mechanistic pathways scrutinized DFT studies, revealed that occurs via C-bound enolate-assisted concerted metalation–deprotonation rate-limiting. subsequent C–C formation steps, lowest energy pathway involves two rhodium carbene species key intermediates.

Language: Английский

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Construction of Axial Chirality by Rhodium‐Catalyzed Asymmetric Dehydrogenative Heck Coupling of Biaryl Compounds with Alkenes

Angewandte Chemie International Edition, Journal Year: 2014, Volume and Issue: 53(48), P. 13244 - 13247

Published: Oct. 24, 2014

Abstract Enantioselective construction of axially chiral biaryls by direct CH bond functionalization reactions has been realized. Novel were synthesized the olefination biaryl compounds, using a [Cp*Rh III ] catalyst, in good to excellent yields and enantioselectivities. The obtained found as suitable ligands for rhodium‐catalyzed asymmetric conjugate additions.

Language: Английский

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