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An efficient conversion of 5-nitroisatin into 5-nitroindole derivative
Y Torisawa1, T Nishi, J Minamikawa
1Process Research Laboratory, Second Tokushima Factory, Otsuka Pharmaceutical Co. Ltd., Japan. torisawa@fact.otsuka.co.jp
Bioorganic & Medicinal Chemistry Letters
|March 30, 2001
Summary
A novel Itsuno system using zirconium tetrachloride and sodium borohydride rapidly converts N-alkyl-nitroisatins to nitroindoles. This mixed reducing agent system is superior to others for synthesizing the nitroindole nucleus.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Isatin derivatives are important precursors in medicinal chemistry.
- Efficient synthesis of the nitroindole nucleus is crucial for drug discovery.
Purpose of the Study:
- To develop a rapid and direct method for synthesizing the nitroindole nucleus.
- To evaluate the efficacy of a mixed borohydride reducing agent system.
Main Methods:
- Process research utilizing a mixed borohydride reducing agent (zirconium tetrachloride/sodium borohydride) in dimethoxyethane (DME).
- Comparative analysis of various reducing agents.
- Development of an N-alkylation procedure for base-labile isatin using copper(II) carbonate.
Main Results:
- The Itsuno system (ZrCl4/NaBH4 in DME) achieved rapid and direct conversion of N-alkyl-nitroisatins to the nitroindole nucleus.
- The ZrCl4/NaBH4 system demonstrated superiority over other reducing agents.
- A new N-alkylation method for isatin using Cu2CO3 was established.
Conclusions:
- The developed Itsuno system offers an efficient route to nitroindoles.
- Zirconium tetrachloride plays a key role in the reduction process.
- The new N-alkylation procedure facilitates isatin manipulation.