PURPOSE: To epoxidize an olefin in low catalyst concn. with high selectively by oxiginzing the olefin with H2O2 in the presence of dimeric dioxo-compd., etc., of μ-oxo ]Mo -oxo-(5,10, 15,20-tetra -phenylporphyrin) ]2.

CONSTITUTION: In the case of catalytic epoxidizing reaction of an olefin by H2O2 in the presence of dimeric dioxo-compd. of μ-oxo ]Mo -oxo-(5,10, 15,20 -tetraphenylporphyrin) ]2, bisperoxo compd. of trans -diperoxo-molibedenum(IV)5,10, 15,20 -tetraphenylporphyrin or cisdioxo -5,10, 15,20 -tetraphenylporphyrinatomolybdenum(IV) -complex in homogenous phase or in two phases, the epoxy compds. are obtnd. with high yield by using the compd., wherein the phenyl group of ligand -5,10,15,20-tetraphenyporphyrin is substd. with one or more halogen atom, OH, a 1-6C-alkyl group, etc.