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Solid-phase synthesis of 5-substituted amino pyrazoles
Dharmpal S Dodd1, Rogelio L Martinez, Muthoni Kamau
1Early Discovery Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 4000, Princeton, New Jersey 08543-4000, USA. dharmpal.dodd@bms.com
Journal of Combinatorial Chemistry
|July 12, 2005
Summary
A new solid-phase synthesis method efficiently produces 5-N-alkylamino and 5-N-arylamino pyrazoles. This mild and general approach uses readily available resin-immobilized beta-ketoamides as starting materials.
Area of Science:
- Organic Chemistry
- Medicinal Chemistry
- Synthetic Chemistry
Background:
- Pyrazole derivatives are important scaffolds in medicinal chemistry.
- Developing efficient and versatile synthetic routes for substituted pyrazoles is crucial.
- Solid-phase synthesis offers advantages in purification and automation.
Purpose of the Study:
- To develop an efficient solid-supported synthesis method for 5-N-alkylamino and 5-N-arylamino pyrazoles.
- To utilize readily accessible resin-immobilized beta-ketoamides as starting materials.
- To establish a general and mild synthetic protocol.
Main Methods:
- Resin-immobilized beta-ketoamides were used as starting materials.
- Reaction with aryl- or alkylhydrazine and Lawesson's reagent in THF/Py mixture.
- Heating at 50-55°C to yield resin-bound 5-aminopyrazoles.
- Cleavage from the solid support using trifluoroacetic acid (TFA).
Main Results:
- An efficient solid-phase synthesis of 5-N-alkylamino and 5-N-arylamino pyrazoles was achieved.
- The method is general, accommodating various alkyl and aryl substituents.
- The reaction conditions are mild, preserving sensitive functional groups.
- Purification is simplified due to the solid-support approach.
Conclusions:
- This study presents a robust and efficient solid-phase method for synthesizing diverse 5-aminopyrazoles.
- The described protocol is suitable for library synthesis and drug discovery efforts.
- The use of resin-immobilized beta-ketoamides provides a practical route to valuable pyrazole derivatives.