Auxiliary-directed peroxidation of 1,4-dienes

Article abstract of DOI:10.1016/0040-4020(96)00744-2

The addition of singlet oxygen (¹O₂) to the proximal alkene of auxiliary-tethered 1,4-dienes and the addition of triplet oxygen ³O₂) to the proximal position of the corresponding pentadienyl radicals both produce conjugated diene hydroperoxides in moderate to high diastereomeric excess. Negligible stereoselection is observed for additions of ¹O₂ to the distal alkene of Z,Z-heptadienes due to the lack of control of alkene conformation. Despite evidence for the intermediacy of highly constrained pentadienyl radicals, poor diastereoselection is also observed for distal addition of ³O₂. The extent of olefin isomerization observed during radical oxygenations can be correlated with steric constraints on the intermediate pentadienyl and peroxyl radicals and may be relevant to literature reports of olefin isomerization during enzymatic oxygenations of unnatural fatty acids.