Copper-Catalyzed Cascade Coupling/Cyclization/Switchable aza-Claisen Rearrangement for Indole Skeletons

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Indole derivatives are crucial scaffolds in medicinal chemistry.
• Existing synthetic methods often lack diversity and efficiency.

Purpose of the Study:

• To develop a novel, efficient, and divergent synthesis of substituted indole derivatives.
• To explore the use of diazo compounds as versatile coupling partners.
• To investigate the role of organic bases in controlling reaction pathways.

Main Methods:

• Copper-catalyzed cascade reaction involving coupling, cyclization, and aza-Claisen rearrangement.
• Utilized N-allyl-2-alkynylanilines and diazo compounds as starting materials.
• Employed triethylamine as a switchable catalyst to control rearrangement pathways.

Main Results:

• Successfully synthesized 2,3-disubstituted, C3-allylated, and C2-but-3-en-1-ylated indole derivatives.
• Demonstrated the expanded functional group tolerance at the C2 position using diazo compounds.
• Showcased the switchable nature of the aza-Claisen rearrangement controlled by triethylamine.

Conclusions:

• A novel copper-catalyzed cascade reaction provides a divergent synthetic route to functionalized indoles.
• The use of diazo compounds significantly broadens the scope of accessible indole structures.
• Triethylamine acts as an effective chemical switch, enabling control over distinct reaction pathways.