Kinetic resolution of acyclic secondary allylic silyl ethers catalyzed by chiral ketones

Kinetic resolution of acyclic secondary allylic silyl ethers by chiral diox iranes generated in situ from chiral ketones (R)-1 and (R)-2 and Oxone was investigated. An efficient and catalytic method has been developed for kine tic resolution of those substrates with a CCl3, tert-butyl, or CF3 group at the alpha -position. In particular, high selectivities (S up to 100) were observed for kinetic resolutions of racemic alpha -trichloromethyl allylic silyl ethers 7 and 9-15 catalyzed by ketones (R)-2. Both the recovered subs trates and the resulting epoxides were obtained in high enantiomeric excess . On the basis of steric and electrostatic interactions between the chiral dioxiranes and the racemic substrates, a model was proposed to rationalize the enantioselectivities and diastereoselectivities in the chiral ketone-ca talyzed kinetic resolution process.