New chiral amino-phosphoramidite and bisphosphoramidite ligands derived from (R,R)-1,2-diaminocyclohexane:: application in Cu-catalyzed asymmetric conjugate addition of diethylzinc to 2-cyclohexenone

New bidentate amino-phosphoroamidite and diphosphoroamidite ligands derived from inexpensive (R,R)-1,2-diaminocyclohexane have been synthesized and screened in the Cu-catalyzed asymmetric conjugate addition of Et2Zn to 2-cyclohexenone. The highest 74% ee value was reached with the N,N'-dimethyl substituted P,N-ligand and Cu(OAc)(2).H2O. (C) 2003 Elsevier Ltd. All rights reserved.