1,8-Di(2-ethynylaryl)biphenylenes: Palladium-Catalyzed Intramolecular Cycloisomerization and Subsequent Thermal...

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Catalysis

Background:

• 1,8-dibromobiphenylene serves as a key substrate in organic synthesis.
• Suzuki coupling reactions are fundamental in C-C bond formation.
• Palladium-catalyzed reactions enable complex molecular transformations.

Purpose of the Study:

• To investigate a novel cascade reaction for synthesizing unusual fused ring systems.
• To explore the mechanism of palladium-catalyzed cycloisomerization and thermal rearrangement.
• To determine the scope and limitations of this synthetic methodology.

Main Methods:

• Utilizing a cascade reaction involving 1,8-dibromobiphenylene and arylboronic acid.
• Employing palladium catalysis for cycloisomerization.
• Characterizing products using X-ray crystallography.

Main Results:

• An unprecedented palladium-catalyzed cycloisomerization of an initial Suzuki product was achieved.
• A unique 5-8-5-membered ring framework was successfully synthesized.
• The intermediate product typically underwent thermal rearrangement to yield the final target molecule.
• The reaction scope, limitations, and mechanism were elucidated.

Conclusions:

• A novel and efficient cascade reaction for constructing complex fused ring systems has been developed.
• The study provides mechanistic insights into palladium-catalyzed cycloisomerization and subsequent thermal rearrangement.
• The synthetic strategy offers a new route to molecules with unique polycyclic frameworks.