Asymmetric epoxidation of α,β-unsaturated ketones using α,α-diarylprolinols as catalysts

Abstract

Asymmetric epoxidation of , -unsaturated ketones has been extensively studied and several important procedures have been developed in the last decade. This review addresses the most significant advances in asymmetric epoxidation of , -unsaturated ketones using proline-derived , -diarylprolinols as catalysts. Special attention has been paid to the enantioselective epoxidation of chalcones, , -unsaturated trifluoromethyl, trichloromethyl ketones and , -unsaturated -keto esters based on the reseach of our group. epoxidation, electron-deficient olefins, organocatalysis, ketone, prolinol Citation:Zheng C W, Zhao G. Asymmetric epoxidation of , -unsaturated ketones using , -diarylprolinols as catalysts.Optically active epoxides are highly useful intermediates and building blocks for the synthesis of biologically active compounds. Various effective systems have been developed over the years for the preparation of chiral epoxides [1]. Among the many powerful methods for the enantioselective epoxidation of olefins, metal-catalyzed epoxidation of allylic alcohols with chiral titanium catalysts [2], epoxidation of allylic [3] and homoallylic [4] alcohols using chiral vanadium catalysts and epoxidation of unfunctionalized olefins using chiral manganese [5] or iron [6] catalysts have proven to be powerful approaches. In recent years, significant progress has been made by Shi [7] on asymmetric epoxidation of various types of olefins catalyzed by chiral ketonesand iminium salts [8], and Shibasaki has developed the epoxidation of electron-deficient olefins catalyzed by La-BINOL-Ph 3 As=O complex which gave a better result [9]. Development of new methodologies, characterized by operational simplicity and use of easily available catalysts, is the main target of modern organic synthesis. Asymmetric organocatalysis offers most of these advantages, since *Corresponding author (email: zhaog@mail.sioc.ac.cn)metal-free and environmentally friendly conditions have been accomplished for many transformations using small organic molecules as chiral promoters. Since the epoxidation of electron-deficient carbonyl compounds [10] using alkaline H 2 O 2 was reported by Weitz-Scheffer, much progress has been made towards the development of an asymmetric variant. Phase-transfer catalysts investigated by Wynberg et al. [11] and polyamino acids developed by Juliá and coworkers [12] for the asymmetric epoxidation of , -unsaturated ketones meant a breakthrough for this type of reactions. Recently, the use of chiral prolinols as organocatalysts has been reported as a new methodology for asymmetric epoxidation of electron-deficient olefins [13,14]. This review describes the progress in this area.