Enantioselective alpha-Fluorination of beta-Ketoesters by Cobalt Catalyst

摘要

Recently, fluorinated compounds have attracted much interest from organic, medicinal, agricultural, and materials chemists. One of the most fascinating aspects of modern organofluorine chemistry is the discovery of efficient methods for enantioselective fluorination. Especially, the transition metal catalyzed enantioselective fluorination is one of the promising methods to introduce the fluorine atom into organic compounds in order to construct chiral fluorinated organic compounds. The pioneering work of the catalytic asymmetric alpha-fluorination of beta-ketoesters using a chiral titanium catalyst was reported by Togni and co-workers in 2000. Also Sodeoka and co-worker reported that a chiral palladium catalyst exhibited a high enantioselectivity in 2002, and they expanded their catalyst system to several compounds. Furthermore, Cahard et al. and Shibata et al. reported the transition metal catalyzed efficient alpha-fluorination of beta-ketoesters using chiral copper and nickel catalysts, respectively. The enantioselectivities of 90% ee can now be achieved using electrophilic reagents, but we believe the development of new catalytic systems for this reaction are still required. We now report the cobalt catalyzed enantioselective alpha-fluorination of beta-ketoesters.