Shapeshifting radicals

Since the synthesis of bullvalene, closed-shell shapeshifting hydrocarbon cages have been extensively studied both experimentally and theoretically. However, considerably less attention has been given to shapeshifting radical hydrocarbon cages. Despite being synthesized over 30 years ago, the shapeshifting barbaralyl radical (CH)₉• has not been studied computationally, and very few experimental studies have been reported. Here, we brush the dust off this shapeshifting radical using the high-level W1-F12 composite ab initio method. We find that consistent with the experimental results, rearrangement of the barbaralyl radical proceeds through a series of β-scission and cyclization steps, which are kinetically favorable over degenerate Cope rearrangements. We proceed to examine these chemical processes in a larger shapeshifting radical cage (CH)₁₁•, which has not been previously investigated. This shapeshifting radical involves a more complex set of rearrangements through β-scissions and cyclizations and is predicted to be less fluxional than the barbaralyl radical.