Stereospecific construction of chiral tertiary and quaternary carbon by nucleophilic cyclopropanation with bis(iodozincio)methane.
The reaction of a ketone having a leaving group at the alpha-position, such as alpha,beta-epoxy ketone or alpha-sulfonyloxy ketone, with bis(iodozincio)methane affords a zinc alkoxide of cyclopropanol. The reaction proceeds by nucleophilic addition of the dizinc to the carbonyl group and a sequential intramolecular nucleophilic substitution of the introduced iodozinciomethyl group to the adjacent electrophilic carbon that has a leaving group. When an optically active alpha,beta-epoxy ketone or alpha-sulfonyloxy ketone is treated with the dizinc, a zinc alkoxide of cyclopropanol having a chiral tertiary or quaternary carbon in the cyclopropane ring is obtained, and the obtained zinc alkoxide of cyclopropanol acts as a chiral homoenolate. When it is treated with an electrophile in the presence of copper cyanide, it gives an optically active alpha-tertiary or -quaternary ketone that retains high optical purity.
Nomura
Kenichi
K
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoutodaigaku-katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Matsubara
Seijiro
S