Catalyst-Controlled Annulations of Strained Cyclic Allenes with π-Allylpalladium Complexes

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Catalysis

Background:

• Strained cyclic allenes are reactive intermediates, known for over 50 years.
• Their synthetic applications, especially with transition metal catalysis, remain underexplored.
• Trapping these fleeting intermediates is challenging but offers pathways to complex molecules.

Purpose of the Study:

• To report the first annulation of strained cyclic allenes with palladium.
• To demonstrate the selective synthesis of polycyclic scaffolds using these intermediates.
• To expand the utility of strained cyclic allenes in complex molecule synthesis.

Main Methods:

• In situ generation of highly reactive cyclic allenes.
• Annulation reactions with in situ-generated π-allylpalladium species.
• Ligand variation to control reaction selectivity and product formation.

Main Results:

• Successful first-time annulation of strained cyclic allenes with palladium.
• Selective synthesis of two distinct isomeric polycyclic scaffolds.
• Formation of heterocyclic, sp3-rich products with multiple stereocenters.

Conclusions:

• This work establishes a new method for utilizing strained cyclic allenes in synthesis.
• The developed methodology allows for rapid assembly of complex molecular architectures.
• It encourages further exploration of transition metal-catalyzed couplings with strained cyclic allenes.