Rhodium-Catalyzed Asymmetric Conjugate Additions of Boronic Acids to enones using DIPHONANE: a novel chiral bisphosphine ligand.
[reaction: see text] The synthesis of a novel enantiopure C2-symmetric bisphosphine, DIPHONANE, was accomplished starting from 2,5-norbornadione, utilizing (R,R)- and/or (S,S)-(2,3-O-di[(phenylamino)carbonyl]tartaric acid for the resolution of an intermediate phosphineoxide. The application of this ligand in the rhodium-catalyzed asymmetric conjugate addition of boronic acids to cyclic enones provides the 1,4-addition products in good yields (69-98%) and high ee's (78-95% ee). A byproduct arising from a consecutive 1,4-addition and 1,2-addition was also observed.
Vandyck
Koen
K
Laboratory for Organic and Bioorganic Synthesis, Department of Organic Chemistry, Ghent University, Krijgslaan 281 (S.4), B-9000 Gent, Belgium.
Matthys
Bavo
B
Willen
Mario
M
Robeyns
Koen
K
Van Meervelt
Luc
L
Van der Eycken
Johan
J