title: A new class of tunable dendritic diphosphine ligands: synthesis and applications in the Ru-catalyzed asymmetric hydrogenation of functionalized ketones.
abstract: A series of tunable G0-G3 dendritic 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligands was prepared by attaching polyaryl ether dendrons onto the four phenyl rings on the P atoms. Their ruthenium complexes were employed in the asymmetric hydrogenation of β-ketoesters, α-ketoesters, and α-ketoamides to reveal the effects of dendron size on the catalytic properties. The second- and third-generation catalysts exhibited excellent enantioselectivities, which are remarkably higher than those obtained from the small molecular catalysts and the first-generation catalyst. Molecular modeling indicates that the incorporation of bulky dendritic wedges can influence the steric environments around the metal center. In addition, the ruthenium catalyst bearing a second-generation dendritic ligand could be recycled and reused seven times without any obvious decrease in enantioselectivity.
authors.affiliation: Beijing National Laboratory for Molecular Sciences and CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190 (P.R. China).
authors.forename: Baode
authors.initials: B
authors.lastname: Ma
authors.forename: Tingting
authors.initials: T
authors.lastname: Miao
authors.forename: Yihua
authors.initials: Y
authors.lastname: Sun
authors.forename: Yanmei
authors.initials: Y
authors.lastname: He
authors.forename: Ji
authors.initials: J
authors.lastname: Liu
authors.forename: Yu
authors.initials: Y
authors.lastname: Feng
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Fan
keywords: asymmetric catalysis; dendrimers; hydrogenation; ligands; ruthenium