Skeletal diversity in small-molecule synthesis using ligand-controlled catalysis.

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Chemistry

Background:

• Palladium-catalyzed reactions are crucial for organic synthesis.
• Controlling reaction pathways is key to accessing diverse molecular structures.

Purpose of the Study:

• To develop selective Pd-catalyzed reductive transformations of silyl ether-tethered diynes.
• To demonstrate ligand control over reaction outcomes (reductive cyclization vs. hydrogenation).

Main Methods:

• Screening of palladium precatalysts, phosphine ligands, and additives.
• Synthesis and reaction of sixteen silyl ether-tethered diynes.
• Optimization of reaction conditions for selective cyclization or hydrogenation.

Main Results:

• Two distinct Pd-catalyzed reductive pathways were established.
• Reaction outcomes were exclusively controlled by the choice of phosphine ligand.
• Silacyclic dienes and silyl-tethered enynes were obtained selectively.
• These products were converted into complex bicyclic and tricyclic small molecules in 1-3 steps.

Conclusions:

• Ligand selection in Pd-catalysis offers precise control over reductive transformations of diynes.
• This approach provides access to diverse, highly substituted small molecules.
• The methodology parallels biosynthetic pathways in directing skeletal diversity through subtle catalyst modifications.