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Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
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Allene Trifunctionalization via Amidyl Radical Cyclization and TEMPO Trapping
Robert M Ward1, Jennifer M Schomaker1
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
The Journal of Organic Chemistry
|June 14, 2021
Summary
This study introduces a novel light-promoted reaction for trifunctionalizing allenes, creating three new carbon-heteroatom bonds in one step without transition metals. The method offers a new pathway for complex molecule synthesis using readily available reagents.
Area of Science:
- Organic Chemistry
- Photochemistry
- Radical Reactions
Background:
- Radical-mediated difunctionalizations of alkenes and alkynes are well-established.
- Radical-mediated trifunctionalizations of allenes remain largely unexplored.
- Development of metal-free catalytic methods is highly desirable.
Purpose of the Study:
- To develop a novel method for the radical-mediated trifunctionalization of allenes.
- To achieve the formation of three new carbon-heteroatom bonds in a single synthetic step.
- To explore a metal-free, light-promoted catalytic system.
Main Methods:
- Photochemical generation of an amidyl radical via an electron donor-acceptor complex.
- In situ cyclization to form a vinyl radical intermediate.
- Trapping of the vinyl radical with TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) to yield the final product.
Main Results:
- Successful one-pot trifunctionalization of allenes, converting all three carbons into C-heteroatom bonds.
- Demonstration of a metal-free catalytic system utilizing visible light.
- Investigation into the influence of allene substitution, radical source, and electron donor on reaction efficiency.
Conclusions:
- A new, efficient, and metal-free method for allene trifunctionalization has been established.
- The developed photochemical strategy provides access to valuable trifunctionalized products.
- The study offers mechanistic insights into this unprecedented radical transformation.
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