title: Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones.
abstract: Two representative Walphos analogues with an achiral 2,2″-biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with aC2-symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands. The application of one newly synthesized ligand in the hydrogenation of 2-methylcinnamic acid gave (R)-2-methyl-3-phenylpropanoic acid with full conversion and with 92% ee. The same ligand was used to transform 2,4-pentanedione quantitatively and diastereoselectively into (S,S)-2,4-pentanediol with 98% ee.
authors.affiliation: Institute of Organic Chemistry, University of Vienna , Währinger Straße 38, A-1090 Vienna, Austria ; Institute of Applied Synthetic Chemistry, Vienna University of Technology , Getreidemarkt 9/163, A-1060 Vienna, Austria.
authors.forename: Afrooz
authors.initials: A
authors.lastname: Zirakzadeh
authors.affiliation: Institute of Organic Chemistry, University of Vienna , Währinger Straße 38, A-1090 Vienna, Austria ; Department of Chemistry, University of Cambridge , Lensfield Road, CB2 1EW Cambridge, U.K.
authors.forename: Manuela A
authors.initials: MA
authors.lastname: Groß
authors.affiliation: College of Pharmaceutical Sciences, Capital Medical University, Beijing , No.10 Xitoutiao, You An Men Beijing 100069, People's Republic of China.
authors.forename: Yaping
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology , Getreidemarkt 9/164SC, A-1060 Vienna, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Mereiter
authors.affiliation: Institute of Organic Chemistry, University of Vienna , Währinger Straße 38, A-1090 Vienna, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Weissensteiner