Hydrocarbon radical cations ring opening

The ubiquitous and reversible formation of radical cations in photoelectrochemical transformations allows pericyclic reactions to take place upon photocatalytic activation since the barriers for pericyclic reactions are often lower in the singly oxidized product than in the neutral precursor. For example, ring openings on irradiated CdS suspensions are known in strained saturated hydrocarbons [176], and formal [2 -I- 2] cycloadditions have been described for phenyl vinyl ether [ 177] and A-vinyl carbazole [178]. The cyclization of nonconjugated dienes, such as norbomadiene, have also been reported [179]. A recent example involves a 1,3-sigmatropic shift [180]. 

Bicyclo[3.1.0]hex-2-ene radical cation, generated by y-irradiation of the respective hydrocarbon in freon matrices at 77 K, underwent ring opening to the 1,3-cyclohexadiene radical cation. " Tris(/7-bromophenyl)aminium hexachloroantimonate oxidized substituted tricyclo[3.3.0.0 ]-octanes to radical cations, which rearranged to diquinanes. ... 

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