摘要:
The catalytic enantio selective addition of different organozinc reagents, such as alkyl or in situ generated phenylzinc derivatives to simple aryl ketones, was accomplished using titanium tetraisopropoxide and chiral ligands derived from trans-1-arenesulfonylamino-2-isoborneolsulfonylamidocyclohexane and Frechet-type dendrons with up to 2.5 nin of diameter, giving the corresponding tertiary alcohols with enantioselectivities up to >99%. A simple and efficient procedure for the synthesis of the ligands used is also described, involving the radical addition of the corresponding thiol dendron to the chiral styryl-isoborneol derivative. (C) 2008 Elsevier Ltd. All rights reserved.