Singlet oxygenation of 4-(4-tert-butyl-3,3-dimethyl-2,3-dihydrofuran-5-yl)-2-pyridone: non-stereospecific 1,4-addition of singlet oxygen to a 1,3-diene system and thermal rearrangement of the resulting 1,4-endoperoxides to stable 1,2-dioxetanes

Singlet oxygen adds easily to a 1,3-diene 1, whose E-Z double bond isomeriz ation can not take place, to give a mixture of stereoisomeric 1,4-endoperox ides 2 which rearranges into a thermally stable 1,2-dioxetane 5 selectively on heating in benzene.