Templ, J., & Schnürch, M. (2025, September 15). A Double Bond Agent on a Mechanochemical Mission - Ball Milling Strategies to Introduce C(sp2)=C(sp2) Bonds [Conference Presentation]. 11th INCOME Conference, Berlin, Germany.
Introducing double bonds into chemical compounds - through vinylation, allylation, or olefination - is a fundamental strategy in organic synthesis, providing reactive handles for further functionalization such as epoxidation, dihydroxylation, metathesis, or radical reactions. Although these transformations are well-established in conventional solution-based chemistry, the introduction of C(sp²)=C(sp²) bonds remains underdeveloped under solvent-free conditions…
…at least until our double bond agent took on the mission.
We demonstrate how these key transformations can be performed under mechanochemical conditions, focusing on three reactions: the Tsuji-Trost allylation, the Wittig olefination, and the Heck coupling under direct mechanocatalysis. Beyond eliminating solvents, these protocols offer notable advantages: reaction times as short as 30 seconds (Wittig olefination), drastically reduced catalyst loadings (0.5 mol% Pd for the Tsuji-Trost allylation), and efficient catalyst recovery - using a palladium milling ball as the active catalyst in the Heck reaction.
Along the way, we tackled what should be close to impossible: the olefination of sugars under neat conditions. Given their low open-chain content, sugars are typically poor substrates for olefination without solvent. The fact that this reaction proceeds cleanly under ball milling conditions challenges conventional expectations in dry-state synthesis.
Finally, we highlight the applicability of these methods to pharmaceutically relevant compounds, demonstrating their practical value beyond proof-of-concept.
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Research facilities:
Zentrum für Kernspinresonanzspektroskopie
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Project title:
Entwicklung von i-BM in der Direkten Kupfer Mechanokatalyse: J 4922 (FWF - Österr. Wissenschaftsfonds)