EPOXIDATION OF OLEFINS CATALYZED BY O=TI(TPP) AS CATALYST

Epoxidation of cyclohexane using O = Ti (TPP) gives only the cyclohexane oxide. cis- and trans-2-hexenes give stereospecifically cis- and trans-epoxides respectively. cis-Stilbene gives only the cis-stilbene oxide. The rates of competitive epoxidation of cycloolefins follows the order: cyclooctene > norbornene > cyclopentene > cycloheptene > cyclohexene showing thereby that olefin is not coordinated rigidly to metal centre. Substitution of electron donating group increases the rate of epoxide formation. Addition of pyridine or imidazole decreases substantially the yield of the epoxide. However, NaHCO3 and Na2HPO4 are found to promote the peroxotitanium porphyrin formation thereby reducing the rate of epoxidation. Formation of peroxotitanium porphyrin and effect of additives etc. show that cis-hydroxo(alkylperoxo)tetraphenylporphinatotitanium is the active species responsible for epoxidation.