Investigating the Reactivity and Selectivity of [3]Cumulenes via Double-Hybrid DFT.

We present an initial foundational theoretical investigation into the reactivity of [3]cumulenes, identifying key factors influencing the reaction selectivity using DLPNO-ωB97X-2/Def2-QZVPP. Our study demonstrates moderate to high selectivity among the three double bonds in substituted [3]cumulenes. Specifically, the [4 + 2] cycloaddition reaction is kinetically favored at the terminal π-bonds and thermodynamically favored at the central π-bond. In certain tetrasubstituted [3]cumulenes, enhanced and reversed kinetic selectivity is predicted. Our findings elucidate the reversed selectivity in tetrafluoro[3]cumulene, attributed to the reduced cumulene distortion energy, and predict similar selectivity in tetramethoxy[3]cumulene due to thermodynamic influences. Future research will focus on additional kinetic factors to enhance the stability and practical application of [3]cumulenes in chemical synthesis.