Highly Diastereoselective Epoxidation Of Protected α-amino Alkenes Catalyzed By Ruthenium Porphyrin/Cl₂PyNO System And Synthesis Of Chiral Estranol Dimers

Epoxidation of unfunctionalized alkenes catalyzed by metalloporphyrins is a subject of tremendous investigations. By tailoring the porphyrin macrocycles with steric hindrance,sophisticated chiral auxiliaries, or strongly electron-withdrawing groups, the homogeneous systems involving these catalysts can exhibit high regio-, shape-, and enantioselectivity and extremely high catalyst turnovers. There is a growing interest in developing ruthenium porphyrin catalysts for carbon-oxygen, bond formation reactions. Extensive studies have demonstrated that ruthenium porphyrins exhibit high stability and remarkable selectivity in catalyzing organic oxidations of alkenes by 2,6-dichloropyridine N-oxide.In this paper, we epoxided the protected α-amino alkenes by using carbonyl 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin ruthenium(II) [Ru(TDCPP)CO] as catalyst and 2,6-dichloropyridine N-oxide (Cl2PyNO) as oxidant. Protected α-amino epoxides were successfully obtained in high threo-selectivity (up to 99%) under mild reaction conditions.On the other hand, we synthesized two new optically axial estrone dimers after acylation, reduction and coupling. We can get higher yield than other methods before(<8.5%). Further more two diastereomers can be separated through simple column chromatography.