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Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Inter-and Intramolecular (4+3) Cycloadditions With Epoxy Allylsilanes as Dienophiles
Qin Han Teo1, Yuchen Zhou2, Elizabeth H Krenske2
1Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Hong Kong, P.R. China.
This study introduces a novel synthesis of methylenated cycloheptanoids using catalytic amounts of triflate (TESOTf). The method employs formal (4+3) cycloadditions, yielding diverse polycyclic compounds.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Cycloaddition reactions are fundamental in organic synthesis for constructing cyclic molecules.
- The development of efficient methods for synthesizing complex cycloheptanoid structures remains an active area of research.
Purpose of the Study:
- To develop a novel synthetic route to methylenated cycloheptanoids.
- To explore the utility of epoxy allylsilanes as dienophiles in (4+3) cycloadditions.
Main Methods:
- Formal (4+3) cycloaddition reactions between dienes and epoxy allylsilanes.
- Catalysis using trifluoromethanesulfonic acid trimethylsilyl ester (TESOTf).
- Utilized various dienes, including furans, cyclopentadiene, pyrroles, thiophenes, and benzenes.
Main Results:
- Successful synthesis of methylenated cycloheptanoids.
- Achieved moderate to good yields of polycyclic adducts.
- Demonstrated both intermolecular and intramolecular cycloaddition pathways.
Conclusions:
- The developed (4+3) cycloaddition strategy provides an efficient pathway to methylenated cycloheptanoids.
- Epoxy allylsilanes are effective dienophiles in TESOTf-catalyzed cycloadditions.
- The methodology is applicable to a range of dienes, enabling access to diverse polycyclic structures.
Related Concept Videos
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Cycloaddition Reactions: Overview
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Cycloaddition Reactions: MO Requirements for Thermal Activation
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Preparation of Epoxides
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...

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