A Two-Step Synthesis of Unprotected 3-Aminoindoles via Post Functionalization with Nitrostyrene
Nicolai A Aksenov1, Nikolai A Arutiunov1, Igor A Kurenkov1
1Department of Chemistry, North Caucasus Federal University, 1a Pushkin St., 355009 Stavropol, Russia.
Molecules (Basel, Switzerland)
|May 13, 2023
Summary
Researchers developed a new, affordable method to synthesize difficult-to-access 3-aminoindoles. This process uses readily available materials and microwave technology for efficient production of valuable indole derivatives.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Medicinal Chemistry
Background:
- 3-Aminoindoles are important heterocyclic compounds with diverse biological activities.
- The synthesis of free 3-aminoindoles is often challenging due to their reactivity and instability.
- Existing methods for 3-aminoindole preparation can be costly or low-yielding.
Purpose of the Study:
- To develop a novel, cost-effective, and efficient method for preparing 3-aminoindoles.
- To provide a reliable route to not easily accessible indole derivatives.
- To explore the transformation of spirocyclic intermediates into valuable aminated indoles.
Main Methods:
- A two-step synthetic strategy was employed.
- The first step involves the reaction of indoles with nitrostyrene catalyzed by phosphorous acid to form 4'-phenyl-4'H-spiro[indole-3,5'-isoxazoles].
- The second step utilizes microwave-assisted heating with hydrazine hydrate to convert the spirocyclic intermediates into the desired 3-aminoindoles.
Main Results:
- The developed method provides a low-cost route to 3-aminoindoles.
- The intermediate spiro[indole-3,5'-isoxazoles] were successfully synthesized.
- The conversion to 3-aminoindoles using hydrazine hydrate under microwave irradiation proceeded in good to excellent yields.
Conclusions:
- A novel and efficient synthetic pathway for the preparation of 3-aminoindoles has been established.
- This method offers a practical and economical approach for accessing valuable indole derivatives.
- The use of microwave-assisted heating significantly improves the yield and reaction time for the final transformation.
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