Visible Light-Mediated Spiroannulation of o-Alkynyl Acrylamides Using Excited-State Palladium Catalysis

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Spirocyclic compounds are prevalent in natural products and pharmaceuticals, necessitating efficient synthetic strategies.
• Palladium-catalyzed reactions are powerful tools for C-C bond formation and molecular construction.
• Radical-mediated cyclizations offer unique pathways to complex ring systems.

Purpose of the Study:

• To develop a novel photoinduced, palladium-catalyzed spiroannulation reaction.
• To synthesize complex tetracyclic spirocyclic systems from 1,7-enynes.
• To establish a mild and efficient method for accessing diverse spiroannulated molecular architectures.

Main Methods:

• Photoinduced palladium catalysis.
• Radical addition/cyclization cascade initiated by alkyl halides.
• Spiroannulation of *o*-alkynyl acrylamides.

Main Results:

• Successful development of a Pd-catalyzed spiroannulation of 1,7-enynes.
• Formation of spiroannulated tetracyclic systems via radical cascade.
• Demonstrated good scope and functional group tolerance under mild conditions.

Conclusions:

• The developed protocol provides expedient access to complex spirocyclic molecular architectures.
• The use of simple alkyl halides as radical precursors is effective.
• This method offers a valuable addition to the synthetic chemist's toolkit for constructing spirocycles.