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Vertically π-Expanded Coumarins: The Synthesis and Optical Properties.
Rashid Nazir1, Anton J Stasyuk1, Daniel T Gryko1
1Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
The Journal of Organic Chemistry
|November 5, 2016
Summary
Researchers developed a regioselective synthesis for naphtho[2,1,8-def]coumarins using an intramolecular Friedel-Crafts reaction. This method yields planar, tetracyclic products with unique photophysical properties, including strong fluorescence.
Area of Science:
- Organic Synthesis
- Materials Chemistry
- Photophysics
Background:
- Naphtho[2,1,8-def]coumarins are a class of planar, tetracyclic compounds.
- Previous synthetic routes were less efficient or regioselective.
Purpose of the Study:
- To develop a concise and regioselective synthesis of naphtho[2,1,8-def]coumarins.
- To investigate the photophysical properties of the synthesized compounds.
Main Methods:
- Pechmann reaction of 2-naphthols with acetone-1,3-dicarboxylates.
- Intramolecular Friedel-Crafts reaction of benzo[f]coumarins.
- Intermolecular oxidative aromatic coupling.
- Photophysical and computational studies.
Main Results:
- A regioselective synthesis of naphtho[2,1,8-def]coumarins was achieved via intramolecular Friedel-Crafts reaction.
- The 5-hydroxy-naphtho[2,1,8-def]coumarin exhibited highly bathochromically shifted absorption and emission.
- Synthesized coumarin-phenols and their derivatives showed strong greenish-yellow fluorescence, dependent on solvent polarity.
Conclusions:
- The developed synthetic route provides efficient access to novel naphtho[2,1,8-def]coumarins.
- These compounds possess interesting photophysical properties, making them potential candidates for fluorescent materials.
- Solvent polarity significantly influences the observed fluorescence characteristics.
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