AUXILIARY-DIRECTED PEROXIDATION OF 1,4-DIENES

The addition of singlet oxygen (O-1(2)) to the proximal alkene of auxi liary-tethered 1,4-dienes and the addition of triplet oxygen (O-3(2)) to the proximal position of the corresponding pentadienyl radicals bot h produce conjugated diene hydroperoxides in moderate to high diastere omeric excess. Negligible stereoselection is observed for additions of O-1(2) to the distal alkene of Z,Z-heptadienes due to the lack of con trol of alkene conformation. Despite evidence for the intermediacy of highly constrained pentadienyl radicals, poor diastereoselection is al so observed for distal addition of O-3(2). The extent of olefin isomer ization observed during radical oxygenations can be correlated with st eric constraints on the intermediate pentadienyl and peroxyl radicals and may be relevant to literature reports of olefin isomerization duri ng enzymatic oxygenations of unnatural fatty acids. Copyright (C) 1996 Elsevier Science Ltd