B(C₆F₅)₃/I₂ co-mediated cascade [4 + 2]/[3 + 2] cyclization to access spiroimidazolines

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Synthetic Chemistry

Background:

• Spirocyclic compounds are important scaffolds in medicinal chemistry.
• Efficient and sustainable synthetic methods are needed for novel spirocyclic compounds.

Purpose of the Study:

• To develop a highly step- and atom-economical cascade cyclization for novel spiroimidazolines.
• To establish a practical, metal-free, and sustainable synthetic route.

Main Methods:

• A cascade [4 + 2]/[3 + 2] cyclization reaction.
• Catalysis using 1 mol% B(C6F5)3 and I2.
• One-pot synthesis from three readily available starting materials.

Main Results:

• Synthesis of structurally novel spiroimidazolines.
• High yields (up to 88%) and diverse product library.
• Demonstrated high step- and atom-economy and operational simplicity.

Conclusions:

• The developed method provides a practical and sustainable approach to privileged spiro scaffolds.
• The reaction is metal-free, efficient, and utilizes readily available starting materials.
• The synthesized spiroimidazolines have potential applications in medicinal chemistry.