Copper-Catalyzed 2H-Azirine Ring Expansion: An Efficient Route to N-Substituted Pyrazoles

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Medicinal Chemistry

Background:

• Pyrazole derivatives are crucial scaffolds in medicinal chemistry.
• Conventional pyrazole synthesis methods often involve harsh conditions or hazardous reagents.

Purpose of the Study:

• To develop an efficient and sustainable synthetic route to N-substituted pyrazoles.
• To utilize 2H-azirine-2-carbaldehyde as a key synthon in a novel cascade reaction.

Main Methods:

• Copper-catalyzed intramolecular azirine ring-opening.
• Cascade sequence involving N-N bond formation.
• Reaction under mild conditions with broad functional group tolerance.

Main Results:

• Successful synthesis of N-substituted pyrazoles in good to excellent yields.
• Demonstrated tolerance for various amines (aryl amines, sulfonamides, tosylamine).
• Rapid assembly of drug-like scaffolds, including celecoxib analogs.

Conclusions:

• The developed methodology provides a sustainable and practical alternative for pyrazole synthesis.
• The method is highly versatile and applicable in medicinal chemistry for drug discovery.