Synthesis of Conjugated Linear and Cyclic Polyynes by Alkyne Metathesis

The formation of polyynes with an odd number of conjugated triple bonds is synthetically demanding. To address this problem, we have developed and optimized the synthesis of triynes via alkyne metathesis of diynes using molybdenum catalysts. We demonstrate the potential of this method through the synthesis of more challenging and complex products, including macrocycles containing triynes, a pentayne, and triyne precursors to [7]cumulenes. The key to the success of the proposed methodology is achieving a balance between the selectivity and reactivity of the molybdenum and diyne precursors, which requires optimization of both steric hindrance and electronic factors.