New Bidentate Chiral Phosphoramidites In Copper-catalyzed Asymmetric 1,4-addition Of Diethylzinc To Cyclic Alpha,beta-enones: Enantioselective Tandem 1,4-addition-aldol Reactions With 2-cyclopentenone
New bidentate phosphoramidites were prepared starting from alpha,alpha,alpha',alpha'-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (TADDOL) or 1,1-bi-2-naphthol (BINOL) and either 1,2-ethylene- or 1,3-propylenediamine N,N'-disubstituted with achiral or chiral groups. The use of these ligands in the copper-catalyzed enantioselective conjugate addition of diethylzinc to 2-cyclohexenone and 2-cyclopentenone afforded products with e.e.s of up to 89 and 83%, respectively.
