Abstract
A series of 20 one chiral epoxides were obtained with excellent yields (up to 99%) and enantioselectivities (up to >99% ee) using hybrid amide-based Cinchona alkaloids. Our method is characterized by low catalyst loading (0.5 mol %) and short reaction times. Moreover, the epoxidation process can be carried out in 10 cycles, without further catalyst addition to the reaction mixture. This methodology significantly enhance the scale of the process using very low catalyst loading.
Highlights
A series of 20 one chiral epoxides were obtained with excellent yields (up to 99%) and enantioselectivities (up to >99% ee) using hybrid amide-based Cinchona alkaloids
With the growing demand for green and sustainable chemistry, the development of environmentally benign and cheap catalysts remains a great challenge in stereocontrolled organic synthesis.[6]
Alternative methods to improving the abilities of Cinchona-based catalysts were presented by the Park[14] and Siva[15] groups, who showed that adding surfactants to reaction mixtures or using ultrasound support increased the enantiomeric excess of products formed
Summary
A series of 20 one chiral epoxides were obtained with excellent yields (up to 99%) and enantioselectivities (up to >99% ee) using hybrid amide-based Cinchona alkaloids. Alternative methods to improving the abilities of Cinchona-based catalysts were presented by the Park[14] and Siva[15] groups, who showed that adding surfactants to reaction mixtures or using ultrasound support increased the enantiomeric excess of products formed. We began the present study with epoxidation of model Echalcone S1 using cinchonidine-based catalyst C1, leading to product P1 with high yield (91%), but low enantioselectivity (29% ee), as shown in Scheme 1.
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