title: New dihydroxy bis(oxazoline) ligands for the palladium-catalyzed asymmetric allylic alkylation: experimental investigations of the origin of the reversal of the enantioselectivity.
abstract: The origin of the reversal of the enantioselectivity in the palladium-catalyzed allylic alkylation of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate anion using chiral dihydroxy bis(oxazoline) "BO" ligands derived from (1S,2S)-(+)-2-amino-1-phenyl-1,3-propanediol was investigated. To determine the structural effects of the dihydroxy BO ligand on this unique phenomenon, new homochiral dihydroxy BO ligands were prepared from L-threonine and L-serine and were assessed in the transformation. The results obtained with these novel BO ligands, compared with the one obtained by using the dihydroxy BO ligands derived from (1S,2S)-(+)-2-amino-1-phenyl-1,3-propanediol, reveal that the reversal in the enantioselectivity observed with the dihydroxy BO ligand depends on the structure of the ligand. The effect of different bases used to generate the dimethyl malonate anion was also examined. The results are discussed in terms of the interaction of one hydroxy group in the intermediate pi-allyl palladium complex with the dimethyl malonate anion.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. hassan@zyvex.com
authors.forename: Hassan
authors.initials: H
authors.lastname: Aït-Haddou
authors.forename: Olivier
authors.initials: O
authors.lastname: Hoarau
authors.forename: Dimitri
authors.initials: D
authors.lastname: Cramailére
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pezet
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Daran
authors.forename: Gilbert G A
authors.initials: GG
authors.lastname: Balavoine