Pure crystalline dimesityldioxirane has been synthesized on a preparat
ive scale by photooxidation of dimesityl diazomethane with filtered li
ght in solution at low temperature. The synthetic procedure is a scale
d-up version of a reaction path which has previously been observed in
inert matrices. Mechanistic details of the reaction in solution and st
ructural and spectroscopic properties of the dioxirane, as well as exa
mples of its utilization as an oxidizing reagent are described.