Applications of Ruthenium Hydride Borohydride Complexes Containing Phosphinite and Diamine Ligands to Asymmetric Catalytic Reactions

Abstract

[reaction: see text] A series of novel trans-ruthenium hydride borohydride complexes with chiral phosphinite and diamine ligands were synthesized. They can be used in the asymmetric transfer hydrogenation of aryl ketones, including base-sensitive ones, to give chiral alcohols in moderate to good enantioselectivities (up to 94% ee). They are also efficient catalysts for the Michael addition of malonates to enones with enantioselectivities of up to 90%. This kind of catalyst allows a one-pot tandem Michael addition/H(2) hydrogenation protocol to build structures with multiple chiral centers.

Applications of transition metal complexes containing 3,3′-bis(diphenylphosphinoamine)-2,2′-bipyridine ligand to transfer hydrogenation of ketones

“…An ortho-or para-substituted acetophenone with an electron-donor substituent, i.e., 2-methoxy or 4-methoxy is reduced more slowly than acetophenone (Table 2, Entries 4, 5, 9, 10, 14 and 15) [59]. In addition, the introduction of electron withdrawing substituents, such as F, Cl and Br to the paraposition of the aryl ring of the ketone decreased the electron density of the C]O bond so that the activity was improved giving rise to easier hydrogenation [60,61].…”

Bis(phosphinite) with C2-Symmetric Axis; Effects on the Ruthenium(II)- Catalyzed Asymmetric Transfer Hydrogenation of Acetophenone Derivatives

“…From a practical standpoint, it is of substantial interest to develop highly effective chiral phosphinite ligands for asymmetric catalysis. 40, 41 Noyori and co-workers suggested that the highly skewed position of the naphthyl rings in BINAP was the determining factor for the ligand to be so effective in asymmetric catalytic reactions. 42 Comparison of the structure of BINAP with that of the less effective BINAPO reveals two possible reasons for the difference in their effectiveness as chiral ligands in homogeneous catalysis: 43 (1) The oxygen atom in BINAPO increases the distance between the chiral binaphthyl moiety and the PPh 2 group.…”

A ruthenium(II) bipyridine complex containing a 4,5-diazafluorene moiety: Synthesis, characterization and its applications in transfer hydrogenation of ketones and dye sensitized solar cells

“…As expected, the electronic properties (the nature and position) of the substituents on the phenyl ring of the ketone caused the changes in the extent of reduction. To ensure that the observed results could be attributed to purely electronic effects [43][44][45], para-and ortho-substituted acetophenone derivatives were tested for transfer hydrogenation. The results indicated that strong electron withdrawing substituents, such as F, NO 2 and Cl, speed up the reaction (Table 5).…”