Singlet oxygenation of cycloheptatriene: isolation and characterization of the 1,2-dioxetane

Tetraphenylporphyrin-sensitized photooxygenation of cycloheptatriene afforded the 1,2-dioxetane ($\text{3a}$) in 9% yield, thus completing the set of possible cycloaddition products; the 1,2-dioxetane ($\text{3a}$) is the precursor to the benzaldehyde product, but not the (2+6)-cycloadduct ($\text{2a}$).     

Oxidation of allylic alcohols by dimethyldioxirane: Competition reaction between epoxidation and C-H insertion

Epoxidation of allylic alcohols with dimethyldioxirane is accompanied by oxidation of the hydroxy functionality; thus enone formation increases with decreasing substitution at the C---C double bond; nonetheless, selective epoxidation can be obtained by acylation of the alcohol functionality.