Metal-Catalyzed Transformations of Cyclopropanols via Homoenolates

Sekiguchi, Yoshiya; Yoshikai, Naohiko

doi:10.1246/bcsj.20200270

Cited by 39 publications

(11 citation statements)

References 88 publications

(48 reference statements)

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“…The cyclopropane ring has attracted the attention of synthetic chemists over decades for its high strain-driven reactivity as well as for its presence in many biologically active substances . Among all cyclopropanes, cyclopropanols represent unique three-carbon synthons in synthetic methodology development and total synthesis . They have been extensively explored as precursors to homoenolates and β-keto radicals, formed through two distinct ring-opening pathways, which serve as intermediates of orthogonal reactivity for the synthesis of β-functionalized ketones (Scheme a).…”

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confidence: 87%

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

Sekiguchi

Yoshikai

2021

J. Am. Chem. Soc.

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We report herein a zinc-catalyzed β-allylation of cyclopropanols with Morita–Baylis–Hillman (MBH) carbonates with retention of the cyclopropane ring. The reaction is promoted by a zinc aminoalkoxide catalyst, affording cyclopropyl-fused α-alkylidene-δ-valerolactone derivatives in moderate to good yields. Mechanistic experiments suggest that the present reaction does not proceed via direct β-C–H cleavage of the cyclopropanol, but involves zinc homoenolate and its enolization to generate a key bis-nucleophilic species. α-Allylation of this “enolized homoenolate” with MBH carbonate would be followed by regeneration of the cyclopropane ring and irreversible lactonization. The enolized homoenolate mechanism has also been proven to allow for β-functionalization with alkylidenemalononitrile as the reaction partner. A sequence of the present reaction and known cyclopropanol transformation provides an opportunity to transform a simple cyclopropanol into α,β- or β,β-difunctionalized ketones.

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confidence: 87%

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

Sekiguchi

Yoshikai

2021

J. Am. Chem. Soc.

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“…The steric and relativistic effects on metal elements play a crucial role for their bonding characters upon interplay with ligands, thus causing a perturbation to their catalytic abilities . Among a variety of transition metals, however, studies linking the bonding nature with physicochemical properties are rather limited for group 9 metal complexes, while they have been utilized as catalysts in cycloaddition, ring-opening reaction, and C–H activation . This is presumably due to the lability of CpML 2 , readily resulting in decomposition or generation of multinuclear oligomers ([CpML n ] m ) .…”

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confidence: 99%

π-Backbonding on Group 9 Metal Complexes Bearing an η²-(H₂O@C₆₀) Ligand

2022

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As a measure of d-π* back-donation, IR stretching modes are, in general, used for metal carbonyl compounds. Once the ligand is replaced with olefins (metal−arene complexes), it can be analyzed crystallographically unless otherwise the C−C bond length falls into values within standard deviation. Herein, we propose a novel measure using an η 2 -(H 2 O@C 60 ) ligand in group 9 metal− fullerene complexes, in which the stronger d-π* backbonding causes enhanced sp 3character on the coordinated olefinic bond and consequently leads to the restricted rotation for the H 2 O molecule as detectable by the 1 H NMR relaxation time. The π-backbonding strengths were, therefore, found to follow the ascending order of atomic numbers (Co < Rh < Ir) in CpM(CO)(η 2 -H 2 O@C 60 ) (Cp = cyclopentadienyl), associated with the anodic shift on oxidation potentials and hypsochromic shift on absorption edges.

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“…The unique structure and reactivity of metal homoenolates have fascinated chemists for decades due to their homologated enolate structure, in which the β-carbon is nucleophilic . This homologated structure also reveals an electrophilic carbonyl group, leading to its potential as both a nucleophile at the carbon–metal bond and an electrophile at the carbonyl carbon.…”

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Synthesis of 1- and 1,2-Substituted Cyclopropylamines from Ketone Homoenolates

2022

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Ketone homoenolates are intermediates with both nucleophilic and electrophilic properties. While there are several reports on their use as nucleophiles, there are few reports on their potential as electrophiles. Herein, we report the use of ketone zinc/ copper homoenolates as electrophiles in the synthesis of 1-and 1,2substituted cyclopropylamines. We found that CuCN•2LiCl is essential to produce a more reactive homoenolate intermediate. We also report a facile telescoped sequence from β-substituted enones toward 1,2-disubstituted cyclopropylamines.

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Metal-Catalyzed Transformations of Cyclopropanols via Homoenolates

Cited by 39 publications

References 88 publications

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

π-Backbonding on Group 9 Metal Complexes Bearing an η²-(H₂O@C₆₀) Ligand

Synthesis of 1- and 1,2-Substituted Cyclopropylamines from Ketone Homoenolates

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Metal-Catalyzed Transformations of Cyclopropanols via Homoenolates

Cited by 39 publications

References 88 publications

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

Zinc-Catalyzed β-Functionalization of Cyclopropanols via Enolized Homoenolate

π-Backbonding on Group 9 Metal Complexes Bearing an η2-(H2O@C60) Ligand

Synthesis of 1- and 1,2-Substituted Cyclopropylamines from Ketone Homoenolates

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π-Backbonding on Group 9 Metal Complexes Bearing an η²-(H₂O@C₆₀) Ligand