Specific <i>Z</i>-Selectivity in the Oxidative Isomerization of Allyl Ethers to Generate Geometrically Defined <i>Z</i>-Enol Ethers Using a Cobalt(II)(salen) Complex Catalyst

Huang, Guanxin; Ke, Miaolin; Tao, Yuan; Chen, Fen‐Er

doi:10.1021/acs.joc.0c00004

Cited by 42 publications

(36 citation statements)

References 55 publications

(55 reference statements)

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“…Recently, Chen and co‐workers introduced Z ‐enol ethers synthesis from oxidative isomerization of allyl ethers with high geometric control via Co‐catalyzed reaction (path I, Scheme 10). [21] Besides, Lithium diisopropyl amide (LDA) also promotes transformation of allyl ethers to 27 (path II, Scheme 10). [22] …”

Section: Synthesis Of Various Alkyl Enol Ethersmentioning

confidence: 99%

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

Ahmad

Jena

Khan

2021

Chemistry An Asian Journal

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Alkyl enol ethers (AEE) are versatile synthetic intermediates with a unique reactivity pattern. This review article summarizes the synthesis of AEE as well as its reactivity and how enol ether undergoes intermolecular reactions for various bond formation, leading to the construction of several useful organic molecules. The synthetic applications of alkyl enol ethers towards intermolecular bond‐forming reactions include metal‐catalyzed reactions, cycloaddition and heterocycle formation as well as rwactions in the field of natural products synthesis. The achievement of these impressive transformations prove the countless synthetic potential of AEE. The main objective of this review is to bring attentiveness among synthetic chemists to show how AEE extensively can be used to react with both electrophiles as well as nucleophiles, thereby behaving as an ambiphilic reactant. We trust that the unique reactivity pattern of alkyl enol ethers and the fundamental mechanistic idea can attract chemists in AEE chemistry. Exclusively, intermolecular reactions of AEE with other functionalized moieties have not been reviewed to the best of our knowledge.

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Section: Synthesis Of Various Alkyl Enol Ethersmentioning

confidence: 99%

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

Ahmad

Jena

Khan

2021

Chemistry An Asian Journal

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“…The use of this and similar “privileged catalysts” [7] is not limited to oxygen transfer. Highly cis ‐ and enantio‐ or diastereoselective cyclopropanation, [10,11] cross‐coupling, [12] electroreductive alkylation of olefins, [13] epoxide ring opening, [14] aziridination, [15] carbonyl cyanosilylation, [16] or oxidative isomerization of allyl ethers to Z ‐enol ethers [17] have been reported recently, just to name a few.…”

Section: Introductionmentioning

confidence: 99%

Interactions Between Two Cobalt Salen Centers Bridged by Non‐Conjugated Linkers**

Speiser

Zitzer

2021

ChemElectroChem

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Tetra‐tert‐butyl‐Co(salen), an amido‐substituted derivative and a series of bis(salen) complexes of cobalt(II) with the two metal centers bridged by flexible, non‐conjugated bis‐amido linkers are investigated by cyclic voltammetry, chronoamperometry, and differential pulse voltammetry in four electrolytes (acetonitrile or dichloromethane, conventional or weakly coordinating anion). Cyclic voltammograms are analyzed by simulation based on E or EE mechanisms. The compounds are characterized by formal potentials E0 , diffusion coefficients D and number of electrons transferred, n. Differences in the E0 values for the subsequent two one‐electron transfer steps are used as indicators for the interaction between the metal centers in the bis(salen) complexes. The effects of solvent and supporting electrolyte are consistent with the assumption of electrostatic through‐space interactions and coordination to the Co centers. In the dinuclear complexes step‐wise electron transfers according to normal potential ordering makes these compounds “pretenders” in Winter's terms (R.F. Winter, Organometallics 2014, 33, 4517–4536).

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“…Alkene transposition (isomerization) is a synthetic tool that has numerous applications in organic synthesis. − Phenylpropenoids are a particularly popular target based on their numerous applications in fragrance industry, pharmaceuticals, and as building blocks for complex products. , Moreover, there are several tandem transformations involving this transposition of CC double bonds, which enable rapid diversification to functionalized compounds. ,− Regioselective − and stereoselective − alkene transposition reactions are atom-economical, but only if there is high selectivity for the desired isomer.…”

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confidence: 99%

“…Dobereiner reported an air-stable Mo precatalyst for Z -selective isomerization ( Z / E = 84:16 for 1-decene), which is activated by p -toluenesulfonic acid . Hilt reported in situ generated cobalt(II) and nickel(II) phosphine mixtures as catalysts for Z -selective isomerization (Co gives Z / E = 85:15 for 1-hexadecene, Ni gives Z / E = 72:28 for 1-decene). , Chen recently reported a cobalt(II) salen complex capable of isomerizing allyl ethers to Z -enol ethers with high Z -selectivity ( Z / E = 99:1) . Unfortunately, none of these catalysts achieve high selectivity for allylbenzene, which gives biorelevant phenylpropenoid products.…”

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confidence: 99%

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Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism

et al. 2021

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Double-bond transposition in alkenes (isomerization) offers opportunities for the synthesis of bioactive molecules, but requires high selectivity to avoid mixtures of products. Generation of Z-alkenes, which are present in many natural products and pharmaceuticals, is particularly challenging because it is usually less thermodynamically favorable than generation of the E isomers. We report a β-dialdiminate-supported, high-spin cobalt(I) complex that can convert terminal alkenes, including previously recalcitrant allylbenzenes, to Z-2-alkenes with unprecedentedly high regioselectivity and stereoselectivity. Deuterium labeling studies indicate that the catalyst operates through a π-allyl mechanism, which is different from the alkyl mechanism that is followed by other Z-selective catalysts. Computations indicate that the triplet cobalt(I) alkene complex undergoes a spin state change from the restingstate triplet to a singlet in the lowest-energy C−H activation transition state, which leads to the Z product. This suggests that this change in spin state enables the catalyst to differentiate the stereodefining barriers in this system, and more generally that spin-state changes may offer a route toward novel stereocontrol methods for first-row transition metals.

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Specific Z-Selectivity in the Oxidative Isomerization of Allyl Ethers to Generate Geometrically Defined Z-Enol Ethers Using a Cobalt(II)(salen) Complex Catalyst

Cited by 42 publications

References 55 publications

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

Interactions Between Two Cobalt Salen Centers Bridged by Non‐Conjugated Linkers**

Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism

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