Photochemistry of Azocyclopropane

Article abstract of DOI:10.1021/jo00255a016

trans-Azocyclopropane (1t) has been irradiated in the gas phase at 254 nm and in hydrocarbon solution at several wavelengths.As with most acyclic azoalkanes, the dominant reaction is isomarization to the cis-azoalkane 1c.In the gas phase or with short wavelength light, 1t undergoes competitive C-N homolysis, giving cyclopropyl radicals, and ring fragmentation to ethylene.Triplet-sensitized isomerization of the azo linkage proceeds with unusually high efficiency (Φ_t->c=0.2), but no experimental support could be found for the notion that cyclopropane ring cleavage leads to azo group isomerization.Since azocyclopropane behaves as a "reluctant azoalkane" that undergoes multiple photoreactions, it is not a particularly useful source of cyclopropyl radicals.