Cobalt‐Mediated Carbene Transfer Reactions

Cui, Xin; Zhang, X. Peter

doi:10.1002/9781118730379.ch15

Cited by 16 publications

(10 citation statements)

References 92 publications

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“…A catalytic asymmetric dearomatization (CADA) reaction has been proven to be one of the most straightforward methodologies for synthesizing non-flat polycyclic molecules with stereogenic centers from readily available, planar aromatic feedstocks. , You, Johnson, Luan, and Salah have made enormous contributions to this realm. , As part of our ongoing studies to develop dearomatization reactions as well as methodologies using metal–carbene species, , we reported a CADA reaction of phenols with α-diazoamide units (Scheme ). Although the Rh or Cu complexes that are widely used in metal–carbene chemistry , caused a C–H insertion and Büchner reaction, − a Ag complex with a phosphate ligand catalyzed chemoselective phenol dearomatization to furnish enantioenriched spiro compounds. Successful precedents of enantioselective reactions using Ag–carbenes or Ag–carbenoids , are still quite rare, although unique chemoselectivity has been achieved …”

Section: Introductionmentioning

confidence: 99%

Silver-Catalyzed, Chemo- and Enantioselective Intramolecular Dearomatization of Indoles to Access Sterically Congested Azaspiro Frameworks

et al. 2020

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An asymmetric dearomatization of indoles bearing α-diazoacetamide functionalities was developed for synthesizing high-value spiro scaffolds. A silver phosphate chemoselectively catalyzed the sterically challenging dearomatization, whereas more typically used metal catalysts for carbene transfer reactions, such as a rhodium complex, were not effective and instead resulted in a Büchner ring expansion or cyclopropanation. Mechanistic studies indicated that the spirocyclization occurred through a silver-assisted asynchronous concerted process and not via a silver–carbene intermediate. Analyses based on natural bond orbital population and a distortion/interaction model indicated that the degree of C–Ag mutual interaction is crucial for achieving a high level of enantiocontrol. In addition, an oxidative disconnection of a C(sp3)–C(sp2) bond in the product provided unconventional access to the corresponding chiral spirooxindole.

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Section: Introductionmentioning

confidence: 99%

Silver-Catalyzed, Chemo- and Enantioselective Intramolecular Dearomatization of Indoles to Access Sterically Congested Azaspiro Frameworks

et al. 2020

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“…Due to the very reactive nature of the carbene species in most of these processes, transition metals able to stabilize the carbene are often employed. Despite the seminal reports on the use of copper as catalysts in the decomposition of diazo compounds more than 100 years ago, dirhodium carbenoids were reported in the 1970s as viable alternatives , to the more reactive copper carbenoids and they have been extensively investigated. ,,− Other metal complexes including palladium, , iridium, − cobalt, iron, ,− and ruthenium − centers have also been successfully reported to moderate the reactivity of the carbene moiety.…”

Section: Introductionmentioning

confidence: 99%

“…Despite the seminal reports on the use of copper as catalysts in the decomposition of diazo compounds more than 100 years ago, 55 dirhodium carbenoids were reported in the 1970s as viable alternatives 10,56 to the more reactive copper carbenoids and they have been extensively investigated. 36,37,57−67 Other metal complexes including palladium, 68,69 iridium, 70−74 cobalt, 75 iron, 35,76−78 and ruthenium 79−85 centers have also been successfully reported to moderate the reactivity of the carbene moiety. Despite being synthetically very useful, diazo compounds are often associated with their acute toxicity and explosion hazards, especially in the case of the volatile diazomethane.…”

Section: Introductionmentioning

confidence: 99%

Homologation Reaction of Ketones with Diazo Compounds

2016

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This review covers the addition of diazo compounds to ketones to afford homologated ketones, either in the presence or in the absence of promoters or catalysts. Reactions with diazoalkanes, aryldiazomethanes, trimethylsilyldiazomethane, α-diazo esters, and disubstituted diazo compounds are covered, commenting on the complex regiochemistry of the reaction and the nature of the catalysts and promoters. The recent reports on the enantioselective version of ketone homologation reactions are gathered in one section, followed by reports on the use of cyclic ketones ring expansion in total synthesis. Although the first reports of this reaction appeared in the literature almost one century ago, the recent achievements, in particular, for the asymmetric version, forecast the development of new breakthroughs in the synthetically valuable field of diazo chemistry.

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“…In recent years, catalysts suitable for carbene transformations have expanded from those of copper and rhodium to include those of ruthenium, silver, gold, palladium, cobalt, and even zinc, nickel, mercury, and iron . However, most reports have examined only diazo compounds, and they only rarely compared the activities of the reported catalyst with a broader set.…”

Section: Introductionmentioning

confidence: 99%

Reactivity and Selectivity in Catalytic Reactions of Enoldiazoacetamides. Assessment of Metal Carbenes as Intermediates

et al. 2016

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Catalyst effectiveness for metal carbene formation and reactions has been surveyed using N-(tert-butyl)-3-[(tert-butyldimethylsilyl)oxy]-2-diazo-N-(4-chlorobenzyl)but-3-enamide in the formation of the products from both intramolecular C–H insertion and aromatic cycloaddition. Both products are indicators of metal carbene intermediates, and this system provides a means to assess catalysts for metal carbene formation. Donor–acceptor cyclopropene production from the reactant enoldiazoacetamide has been monitored to assess its formation, and the independently formed cyclopropene has also been used to assess metal carbene formation. Catalysts of rhodium(II), copper(I), silver(I), Pd(II), cationic Au(I), and Zn(II) convert the enoldiazoacetamide to the donor–acceptor cyclopropene which serves as the resting state for the intermediate metal carbene, and both the enoldiazoacetamide and its derivative cyclopropene give the same ratios of insertion to cycloaddition products. Catalysts of copper(II) and ruthenium(II) do not give the cyclopropene as an observable intermediate, and the product ratio from insertion/cycloaddition varies when the reactant is the enoldiazoacetate from that with its derivative cyclopropene. The variation of product ratio with the metal carbene precursor in copper(II)-catalyzed reactions is dependent on the catalyst ligand, the solvent, and substituents of the benzyl group of the reactant. [Ru(p-cymene)Cl2]2 formed the products from a metal carbene intermediate with the reactant enoldiazoacetamide catalytically but with an enoldiazoacetate formed a η3-allyl ruthenium complex stoichiometrically.

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Cobalt‐Mediated Carbene Transfer Reactions

Cited by 16 publications

References 92 publications

Silver-Catalyzed, Chemo- and Enantioselective Intramolecular Dearomatization of Indoles to Access Sterically Congested Azaspiro Frameworks

Silver-Catalyzed, Chemo- and Enantioselective Intramolecular Dearomatization of Indoles to Access Sterically Congested Azaspiro Frameworks

Homologation Reaction of Ketones with Diazo Compounds

Reactivity and Selectivity in Catalytic Reactions of Enoldiazoacetamides. Assessment of Metal Carbenes as Intermediates

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