Modulating the Thermal Isomerization Barriers of Quadricyclane to Norbornadiene Through Cross-Conjugative Patterns

Abstract

Computations show that thermal isomerizations of quadricyclane to norbornadiene can be modulated by heteroarene substitution. Heteroarenes that are non-cross-conjugated to the norbornadiene double bond increase delocalization of the transition state structure and lower the thermal activation enthalpy (ΔH‡), while cross-conjugated analogs increase ΔH‡ without significantly impacting the storage enthalpy (ΔHstorage).