Highly β-selective epoxidation of the Δ5- and Δ4-unsaturated steroids catalyzed by the silica-supported polyhalogenated ruthenium porphyrin

The ruthenium(II) 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin carbonyl complex has been covalently attached to a 3-aminoporpyl functionalized silica gel. This supported complex is found to efficiently catalyze the epoxidation of the Δ5-unsaturated steroid derivatives with high conversion, epoxide yield and β-selectivity. High β-selectivity is also observed for the epoxidation of a Δ4-unsaturated steroid though the conversion and derivative are low. This new silica-supported polyhalogenated metalloporphrin catalyst can be easily recovered after reaction and has shown high stability over repeated uses. No catalyst leaching is detected in these reactions.