text: A variety of alternative heteroatom oxidation reagents are known, including peroxides (often employed with a transition metal catalyst) and oxaziridines. These reagents do not suffer from the over-oxidation problems and decomposition issues associated with dioxiranes; however, their substrate scope tends to be more limited. Nucleophilic decomposition of dioxiranes to singlet oxygen is a unique problem associated with dioxirane heteroatom oxidations. Although chiral dioxiranes do not provide the same levels of enantioselectivity as other protocols, such as Kagan's sulfoxidation system, complexation to a chiral transition metal complex followed by oxidation affords optically active sulfoxides with good enantioselectivity.
  Oxidation of arenes and cumulenes leads initially to epoxides. These substrates are resistant to many epoxidation reagents, including oxaziridines, hydrogen peroxide, and manganese oxo compounds. Organometallic oxidants also react sluggishly with these compounds, with the exception of methyltrioxorhenium. Peracids also react with arenes and cumulenes, but cannot be employed with substrates containing acid-sensitive functionality.
  The direct oxidative functionalization of C-H bonds is an ongoing problem in oxidation chemistry. Among metal-free systems, dioxiranes are the best oxidants for the conversion of C-H bonds to alcohols or carbonyls. However, some catalytic transition-metal systems, such as White's palladium-sulfoxide system, are able to oxidize C-H bonds selectively.