Unprecedented Enantioselectivity in a Cluster-Based Catalytic System

Abstract

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Homogeneous Catalysis by Organometallic Polynuclear Clusters

“…The authors relate these findings to their prior study, and suggest that a better enantioselectivity can be achieved by employing ligands with a significant steric bulk proximal to the substrate. To this end, Nordlander prepared Walphos substituted tetraruthenium clusters (33a,b) and reported up to excellent enantioselectivity (30 -93% ee) in the hydrogenation of various α,β-unsaturated carboxylic acids [83]. From spectroscopical and single-crystal X-ray diffraction analysis, an unusual bonding of the phosphine ligand was found; one coordinates equatorially whilst the other axially, resulting in chiral cluster frameworks and thus potential diastereomeric mixtures.…”

“…Asymmetric hydrogenation of 29a, 29b, and 31a using tetraruthenium clusters 32 or 33 having chiral ligands as catalysts. Terminal CO molecules have been omitted for clarity,[81][82][83][84].…”

Biferrocene-Based Diphosphine Ligands: Synthesis and Application of Walphos Analogues in Asymmetric Hydrogenations

“…12 Since one Walphos-type ligand proved to be highly suitable for the asymmetric hydrogenation of a 2-isopropylcinnamic acid derivative, 12b an intermediate in the synthesis of the renin inhibitor Aliskiren, these ligands were commercialized and are now available on a technical scale. In addition to hydrogenations, 13 including cluster-based hydrogenations, 14 Walphos-type ligands were successfully applied in a number of other enantioselective catalytic reactions such as cycloadditions, 15 coupling reactions, 16 copper hydride mediated reactions, 17 and others. 18 While originally developed as a potential alternative to BINAP, the Walphos ligand family is now considered a privileged class of ligands in its own right and searches for novel applications are still continuing.…”

Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

“…The versatility of the Fc group in synthesis can be illustrated by some of the diverse compounds (Chart 1) previously documented in the literature. The Fc group can be employed either as a substituent bonded to phosphorus [6] or a metal centre [7] through an ethynyl linker or alternatively as a backbone for accessing primary and secondary phosphines [8], di-and polyphosphines [9,10], nonsymmetric ligands [11][12][13][14] and chiral systems [15][16][17][18]. To date, 1,1 0 -bis(diphenylphosphino)ferrocene (dppf) possibly remains the most iconic example of a phosphorus(III) based ligand containing the Fc moiety [4,[19][20][21][22][23].…”