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Updated: Jun 28, 2026
12:19
Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
Stereoretentive Norrish-Yang Photocyclization Mediated by Hydrogen Bonding
Enrico Sfreddo1, Aleksa Durdevic1, Andrea Palone1
1University of Bologna, Department of Industrial Chemistry Toso Montanari, via Piero Gobetti 85, 40129 Bologna, Italy.
Journal of the American Chemical Society
|June 26, 2026
Summary
This study introduces a stereoretentive Norrish-Yang photocyclization using hydrogen-bonding to control reactive diradicals. This method achieves high enantioenrichment in spirocyclobutanol synthesis, overcoming challenges in stereocontrol for photochemical reactions.
Area of Science:
- Organic Chemistry
- Photochemistry
- Stereoselective Synthesis
Background:
- The Norrish-Yang photocyclization is a key organic reaction forming cyclobutanes.
- Controlling the stereochemistry of this reaction is challenging due to competing reaction pathways and radical scrambling.
- Existing methods struggle to maintain enantiopurity during the photocyclization process.
Purpose of the Study:
- To develop a stereoretentive Norrish-Yang photocyclization for enantiopure aryl alkyl ketones.
- To enable precise conformational control of photogenerated 1,4-diradicals through hydrogen bonding.
- To achieve high enantiospecificity in the synthesis of complex cyclobutane structures.
Main Methods:
- Utilizing hydrogen-bonding units within chiral substrates to guide diradical conformation.
- Employing photochemical conditions to initiate the Norrish-Yang reaction.
- Analyzing reaction products for stereochemical integrity and enantiomeric excess.
Main Results:
- A novel stereoretentive Norrish-Yang photocyclization was achieved.
- Hydrogen-bonding effectively biased diradical pathways towards cyclization, suppressing fragmentation.
- High enantioenrichment and enantiospecificity were observed in the formation of spirocyclobutanol derivatives.
- The method demonstrated effectiveness across various amino-acid-derived substrates.
Conclusions:
- Hydrogen-bond-guided conformational control offers a powerful strategy for stereoretentive photocyclizations.
- This approach overcomes significant challenges in controlling radical reactivity and stereochemistry.
- The developed method provides access to valuable enantioenriched cyclobutane building blocks.
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