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Synthesis, Optical Properties, and Regioselective Functionalization of 4a-Aza-10a-boraphenanthrene
Alberto Abengózar1, Patricia García-García1, David Sucunza1
1Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá , 28871 Alcalá de Henares, Madrid, Spain.
Organic Letters
|June 14, 2017
Summary
Researchers synthesized 4a-aza-10a-boraphenanthrene efficiently. This boron-nitrogen (BN) isostere exhibits weak fluorescence due to a low-energy conical intersection, and allows regioselective functionalization.
Area of Science:
- Organic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Boron and nitrogen (BN) containing heterocycles are valuable isosteres for aromatic systems.
- Phenanthrene is a polycyclic aromatic hydrocarbon with unique electronic and photophysical properties.
- Understanding structure-property relationships in BN-isosteres is crucial for developing new materials.
Purpose of the Study:
- To synthesize a novel BN-isostere of phenanthrene, specifically 4a-aza-10a-boraphenanthrene.
- To investigate the photophysical properties, particularly fluorescence, of this new compound.
- To explore the reactivity and functionalization potential of 4a-aza-10a-boraphenanthrene.
Main Methods:
- Multi-step synthesis from commercially available starting materials.
- Spectroscopic characterization (e.g., NMR, Mass Spectrometry).
- Photophysical measurements (fluorescence spectroscopy).
- Computational studies (e.g., DFT calculations) to investigate excited-state dynamics.
Main Results:
- Successful synthesis of 4a-aza-10a-boraphenanthrene in four steps with a 62% overall yield.
- Observation of weak fluorescence, contrasting with other phenanthrene BN-isosteres.
- Computational analysis revealed a low-energy conical intersection responsible for nonradiative decay.
- Achieved regioselective functionalization at the C-1 position using activated electrophiles.
Conclusions:
- 4a-aza-10a-boraphenanthrene is a readily accessible BN-isostere of phenanthrene.
- Its weak fluorescence is attributed to efficient nonradiative decay pathways.
- The compound exhibits controlled reactivity, enabling selective functionalization for further derivatization.
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