Synthesis of Conjugated Linear and Cyclic Polyynes by Selective Alkyne Metathesis

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Synthesizing polyynes with an odd number of conjugated triple bonds is difficult.
• Existing methods often involve irreversible reactions and kinetic control, limiting complex structures.

Purpose of the Study:

• To develop a new synthetic route for triynes.
• To enable thermodynamic control in polyyne synthesis through reversible C-C bond formation.

Main Methods:

• Molybdenum-catalyzed alkyne metathesis of diynes.
• Utilizing reversible cleavage and formation of carbon-carbon triple bonds.

Main Results:

• Successfully synthesized complex triynes, including precursors to [7]cumulenes, pentaynes, and heptaynes.
• Demonstrated the synthesis of dehydrobenzannulene macrocycles containing triynes.
• Achieved thermodynamic control over the reaction.

Conclusions:

• Molybdenum-catalyzed alkyne metathesis provides a versatile method for synthesizing challenging odd-numbered polyynes.
• Balancing catalyst selectivity and reactivity is crucial for successful diyne precursor transformation.