Gas‐Phase Synthesis of the Elusive Cyclooctatetraenyl Radical (C8H7) via Triplet Aromatic Cyclooctatetraene (C8H8) and Non‐Aromatic Cyclooctatriene (C8H8) Intermediates

The 1,2,4,7‐cyclooctatetraenyl radical (C₈H₇) has been synthesized for the very first time via the bimolecular gas‐phase reaction of ground‐state carbon atoms with 1,3,5‐cycloheptatriene (C₇H₈) on the triplet surface under single‐collision conditions. The barrier‐less route to the cyclic 1,2,4,7‐cyclooctatetraenyl radical accesses exotic reaction intermediates on the triplet surface, which cannot be synthesized via classical organic chemistry methods: the triplet non‐aromatic 2,4,6‐cyclooctatriene (C₈H₈) and the triplet aromatic 1,3,5,7‐cyclooctatetraene (C₈H₈). Our approach provides a clean gas‐phase synthesis of this hitherto elusive cyclic radical species 1,2,4,7‐cyclooctatetraenyl via a single‐collision event and opens up a versatile, unconventional path to access this previously largely obscure class of cyclooctatetraenyl radicals, which have been impossible to access through classical synthetic methods.