title: Dramatic ligand effect in catalytic asymmetric reductive aldol reaction of allenic esters to ketones.
abstract: A general catalytic asymmetric reductive aldol reaction of allenic esters to ketones is described. Two distinct constitutional isomers were selectively produced depending on the reaction conditions. A combination of CuOAc/(R)-DTBM-SEGPHOS/PCy3 as the catalyst predominantly produced gamma-cis-products in high yield with excellent enantioselectivity (up to 99% ee). The reaction was applicable to both aromatic and aliphatic ketones, including unsaturated ketones. On the other hand, CuF-Taniaphos complexes produced alpha-aldol products with high diastereo- and enantioselectivity (up to 84% ee). The new Taniaphos derivative L3, containing di(3,5-xylyl)phosphine and morpholine units, produced optimum results in the alpha-selective reaction. The products are versatile chiral building blocks in organic synthesis. Furthermore, the basic reaction pattern (i.e., conjugate addition-aldol reaction) was extended to a catalytic enantioselective alkylative aldol reaction to ketones using dialkylzinc reagents as the initiator.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Dongbo
authors.initials: D
authors.lastname: Zhao
authors.forename: Kounosuke
authors.initials: K
authors.lastname: Oisaki
authors.forename: Motomu
authors.initials: M
authors.lastname: Kanai
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Shibasaki
mesh_terms: D002384:Catalysis; D004952:Esters; D007659:Ketones / Q000737:chemistry*; D008024:Ligands; D010084:Oxidation-Reduction
chemical_list: D004952:Esters; D007659:Ketones; D008024:Ligands