Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/30890
Title: Cu-catalyzed enantioselective conjugate addition of diethylzinc to cyclic enones with chiral phosphite ligands derived from 1,2 : 5,6-di-O-cyclohexylidene-D-mannitol
Authors: Zhao, QL
Wang, LL
Kwong, FY 
Chan, ASC
Issue Date: 2007
Publisher: Pergamon Press
Source: Tetrahedron : asymmetry, 2007, v. 18, no. 16, p. 1899-1905 How to cite?
Journal: Tetrahedron : asymmetry 
Abstract: A new and readily in situ prepared catalytic system of copper salts with chiral P,N-ligands or aryl diphosphite ligand, which derived from 1,2:5,6-di-O-cyclohexylidene-D-mannitol, 1,1'-binaphthol, and phenyl isocyanate derivatives, were successfully employed in the enantioselective conjugate additions of diethylzinc to cyclic enones with up to 71% ee. Two notable cooperative effects of the stereochemistry of the ligands on the enantioselectivity were observed in the reactions: one between the phenylcarbamate substituent and the axially chiral binaphthyl moiety; another between the stereogenic centers of mannitol and the chiral binaphthol substituents. A significant dependence of the product yield and stereo selectivity on the ring size of the substrate using the ligand 1,2:5,6-di-O-cyclohexylidene3,4-bis [(S)-1,1'-binaphthyl-2,2'-diyl]phosphite-D-mannitol was also observed: 71% ee for 2-cyclopentenone, 62% ee for 2-cyclohexenone, and 40% ee for 2-cycloheptenone.
URI: http://hdl.handle.net/10397/30890
ISSN: 0957-4166
EISSN: 1362-511X
DOI: 10.1016/j.tetasy.2007.07.008
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