Ene-yne metathesis is a convenient route to new and functionalized dienes from the addition of alkenes and alkynes. The dienes made via this reaction can be used for butadiene-polymerization and Diels-Alder reactions which lead to valuable materials like polybutadienes, and pharmaceutical or agrochemicals. Catalysts for ene-yne metathesis are typically ruthenium carbene complexes, like Grubbs catalyst. Unfortunately, reported catalyst loadings are often quite high (typically 3-5 mol %) for even the most active systems, and tolerance of functional groups can be quite poor for the catalysts. Mechanistic and kinetic studies of both ene-yne and olefin metathesis using Grubbs and Hoveyda-Grubbs catalysts give insight on the catalytic cycle as well as numerous decomposition pathways give insight on the limitations and sensitivities of these catalysts. Combining these insights with our own observations on the effects various reaction conditions have on turnover number (TON) and yield, we have we have developed more effective and efficient methods for the synthesis of 2-substituted butadiene products utilizing the Hoveyda-Grubbs 2<sup>nd</sup>generation catalyst. A key observation is that the conditions to obtain a high TON are highly varied based on functional groups on the primary alkyne precursors used in this study. Our studies provide insight into the effect of these functional groups catalytic performance and provide guidance toward scalable synthesis of 2-substituted butadiene molecules.

Optimizing ene-yne metathesis reactions: Understanding how optimal conditions shift with substrate

2019 Fall National Meeting

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