A. practical catalyst system for the asymmetric epoxidation of olefins

Abstract

A complementary ketone to a fructose-derived asymmetric epoxidation catalyst has been developed in the following manner. The synthesis of a previously-reported oxazolidinone catalyst was improved to prepare quantities suitable for use on small scale. Substrate scope was extended to styrenes with a carbocyclic analog of the original oxazolidinone ketone catalyst made in 15 steps from quinic acid. During the course of the studies of the carbocyclic catalysts, we discovered an electronic effect responsible for enhancing secondary orbital interactions and ultimately, enantioselectivity. The origin of the electronic attraction was studied by synthesizing new ketones with varying functionality where the oxazolidinone previously was found. Having obtained information about the nature of the attraction, we prepared a series of aniline substituted oxazolidinone ketones bearing structural and electronic features the aforementioned work found to be beneficial. We observed 86-92% ee for the epoxidation of meta- and para-substituted styrenes with the optimized 4-ethylaniline-derived ketone, and coworkers have observed high ee for a variety of conjugated cis-olefins with this ketone catalyst. Considering the potential usefulness of this catalyst, we optimized the synthesis of the ethyl aniline oxazolidinone ketone as well as the epoxidation conditions themselves so the catalyst preparation and olefin epoxidation can be performed on large scale.