Borane-catalyzed indole synthesis through intramolecular hydroamination
Sebastian Tussing1, Miriam Ohland1, Garrit Wicker1
1Institute of Organic Chemistry, University of Paderborn, Warburger Straße 100, D-33098 Paderborn, Germany. jan.paradies@uni-paderborn.de.
Dalton Transactions (Cambridge, England : 2003)
|January 17, 2017
Summary
Researchers developed a new method for synthesizing 2-substituted indoles using intramolecular hydroamination of 2-alkynyl anilines. This efficient process, catalyzed by B(C6F5)3, also enabled tetrahydroquinoline synthesis.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Methodology
Background:
- Indole derivatives are prevalent in pharmaceuticals and natural products.
- Efficient synthetic routes to substituted indoles are crucial for medicinal chemistry.
- Intramolecular hydroamination offers a direct pathway to nitrogen-containing heterocycles.
Purpose of the Study:
- To develop a novel catalytic method for the synthesis of 2-substituted indoles.
- To explore the utility of B(C6F5)3 as a catalyst in intramolecular hydroamination reactions.
- To investigate a domino hydroamination/hydrogenation sequence for tetrahydroquinoline synthesis.
Main Methods:
- Reaction of 2-alkynyl anilines with catalytic B(C6F5)3 (5 mol%).
- Characterization of intermediates and products using Nuclear Magnetic Resonance (NMR) spectroscopy.
- Structural elucidation of compounds via X-ray crystallography.
Main Results:
- The intramolecular hydroamination of 2-alkynyl anilines yielded 2-substituted indoles in good to excellent yields.
- Reaction intermediates and final products were successfully characterized.
- A domino hydroamination/hydrogenation sequence efficiently produced tetrahydroquinoline 8 in good yield.
Conclusions:
- Catalytic B(C6F5)3 effectively promotes intramolecular hydroamination for indole synthesis.
- The developed methodology provides a facile route to valuable indole scaffolds.
- The domino sequence offers a streamlined approach to tetrahydroquinoline derivatives.
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