Factors affecting the catalytic epoxidation of olefins by iron porphyrin complexes and H₂O₂ in protic solvents

The catalytic epoxidation of cyclohexene by iron(III) porphyrin complexes and H₂O₂ has been investigated in alcohol solvents to understand factors affecting the catalyst activity in protic solvents. The yields of cyclohexene oxide and the Fe^III/II reduction potentials of iron porphyrin complexes were significantly affected by the protic solvents, and there was a close correlation between the product yields and the reduction potentials of the iron porphyrin catalysts. The role of alcohol solvents was proposed to control the electronic nature of iron porphyrin complexes that determines the catalyst activity in the epoxidation of olefins by H ₂O₂. We have also demonstrated that an electron-deficient iron porphyrin complex can catalyze the epoxidation of olefins by H ₂O₂ under conditions of limiting substrate with high conversion efficiency in a solvent mixture of CH₃OH and CH ₂Cl₂.