The preparative scale synthesis of dimesityldioxirane (5) via oxidation of dimesitylcarbene (6) is described. The dioxirane was obtained as colorless crystalline material, completely stable at-20° C and characterized by spectroscopic methods, X-ray crystallography, and DFT calculations (B3LYP/6-31G (d)). The molecule shows approximately local C 2 symmetry with the mesityl rings twisted by ca. 60°. The experimental structural parameters, eg, the OO ...