Addition of ozone to E- or Z- 1,2-dimethoxy- 1,2-diphenylethene, E- or Z-1, in inert solvents results in formation of approximately 1 mole of methyl benzoate, approximately 0.5 and approximately 0. 1 mole of the corresponding oxiranes 2 and dioxetanes 3, respectively, and 0.03 mole of 3,6-dimethoxy-3,6-diphenyl-1,2,4,5-tetroxane 4 at -20-degrees-C. Product distributions vary with starting material, initial concentration, extent of reaction, and temperature. At -70-degrees-C -0.3 mole of trans-2 and 0.2 mole of cis-and trans-4 are formed from E-1. Addition of E- or Z-1 to solutions of excess ozone results in formation of up to 0.7 mole of (methoxy)phenyldioxirane 5, which is a strong, stereospecific epoxidizing agent