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06:46
Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Phase-transfer-catalyzed asymmetric acylimidazole alkylation
Merritt B Andrus1, Michael A Christiansen, Erik J Hicken
1Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA. mbandrus@chem.byu.edu
Organic Letters
|October 20, 2007
Summary
This study introduces a new method for alkylating 2-acylimidazoles using phase-transfer catalysis, achieving high yields and enantioselectivity. The resulting products can be easily converted into valuable esters without racemization.
Area of Science:
- Organic Chemistry
- Asymmetric Synthesis
- Catalysis
Background:
- 2-Acylimidazoles are versatile synthetic intermediates.
- Efficient enantioselective alkylation methods are crucial for synthesizing chiral molecules.
Purpose of the Study:
- To develop a novel enantioselective alkylation of 2-acylimidazoles.
- To establish a scalable and efficient synthetic route to chiral ester products.
Main Methods:
- Phase-transfer catalysis utilizing cinchonidinium catalysts.
- Alkylation of 2-acylimidazoles with allyl and benzyl electrophiles at -40°C.
- Conversion of alkylated products to esters using methyltriflate and sodium methoxide.
Main Results:
- High yields and excellent enantioselectivity (79 to >99% ee) achieved in the alkylation step.
- Synthesis of 2-acylimidazole substrates in three steps from bromoacetic acid.
- Facile conversion of products to esters without racemization via a dimethylacylimidazolium intermediate.
- Demonstration of S-product formation with high purity catalyst under mild conditions.
Conclusions:
- The developed method provides an efficient and direct route for enantioselective alkylation of 2-acylimidazoles.
- The process is amenable to various electrophiles and transformations involving enolate intermediates.
- This methodology offers a valuable tool for the synthesis of chiral compounds.
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