Enantioselective addition of organozinc reagents to ketones catalyzed by grafted isoborneolsulfonamide polymers and titanium isopropoxide

Abstract

The catalytic enantioselective addition of different organozinc reagents, such as diethylzinc, or in situ generated phenylzinc derivatives to simple aryl methyl ketones was accomplished using titanium tetraisopropoxide and a polymeric ligand grafted with trans-1-phenylsulfonylamino-2-isoborneolsulfonylamidocyclohexane, to give the corresponding tertiary alcohols with enantioselectivities of up to >99% ee. Whereas the highest enantioselectivities were obtained in the ethylation process, the highest chemical yields were obtained in the phenylation process. The ligand could be re-used at least three times without any significant loss of activity.