Cycloadditions of Cyclopentadiene and Cycloheptatriene with Tropones: All Endo-[6+4] Cycloadditions Are Ambimodal

The cycloadditions of cyclopentadiene and cycloheptatriene with tropone are some of the earliest published examples of [6+4] cycloaddition reactions. We report quantum mechanical studies (omega B97X-D and DLPNO-CCSD(T)) of transition structures and products of these reactions, as well as quasi-classical molecular dynamics simulations of reaction trajectories. The study reveals that these cycloadditions involve ambimodal transition states resulting in a web of products by pericyclic interconversion pathways. Combined with these studies, calculations of simple parent systems and a thorough meta-analysis of literature examples reveal the general concept that all endo-[6+4] cycloadditions are ambimodal.

Automated summary

Through quantum mechanical studies and molecular dynamics simulations, it was found that the cycloadditions of cyclopentadiene and cycloheptatriene with tropone involve ambimodal transition states, leading to a complex network of products. This general concept was supported by calculations of simple parent systems and a thorough meta-analysis of literature examples.