Ruthenacycles and Iridacycles as Catalysts for Asymmetric Transfer Hydrogenation and Racemisation

Abstract

Ruthenacycles, which are easily prepared in a single step by reaction between enantiopure aromatic amines and [Ru(arene)Cl 2 ] 2 in the presence of NaOH and KPF 6 , are very good asymmetric transfer hydrogenation catalysts. A range of aromatic ketones were reduced using isopropanol in good yields with ee's up to 98%. Iridacycles, which are prepared in similar fashion from [IrCp*Cl 2 ] 2 are excellent catalysts for the racemisation of secondary alcohols and chlorohydrins at room temperature. This allowed the development of a new dynamic kinetic resolution of chlorohydrins to the enantiopure epoxides in up to 90% yield and 98% enantiomeric excess (ee) using a mutant of the enzyme Haloalcohol dehalogenase C and an iridacycle as racemisation catalyst.

Catalytic sugar-assisted transfer hydrogenation with Ru(II), Rh(III) and Ir(III) halfsandwich complexes

“…The ligand degradation, the role of the substitution pattern of the arene ligand, the pseudo-enantiomeric behavior of the epimeric ligands 1 and 2 and the preference for the formation of a certain enantiomer of 1-phenylethanol will be discussed in the following parts of this publication. [20,29,30,32,33]. …”

“…The concept to prevent two active sites of the Noyori-type catalyst is to discriminate the amino groups [29][30][31][32][33][34][35][36]. This is usually achieved by p-toluenesulfonylation of one of the amino groups.…”

“…The results for catalyst precursors 26-30 (Chart 2) inTable 4(entries 29-34) are cited from publications of Noyori's and other groups[20,29,30,32,33].…”

Synthesis of a novel magnetic nanocatalyst based on rhodium complex for transfer hydrogenation of ketone

“…This is because alcohols have important applications as intermediates in manufacturing of pharmaceuticals, fragrances, agrochemical, advanced materials, and etc. These alcohols are usually prepared through catalytically prompted hydrogenation of ketones . The preferable way to achieve this transformation is the reduction of ketones by hydrogen donor reagents, other than the potentially dangerous hydrogen gas, which is achieved in the presence of a suitable catalyst.…”

Part I Synthesis, characterization and reactivity studies on Ir(III) and Ru(IV) complexes with sulfur ligands Part II Catalytic applications of Ru and Pd metallacycles in C-C and C-P bond formations

“…29 However, examples of DTC complexes involving organoruthenium (IV) still remains scarce. 27,30 The compound [(η 3 :η 3 thioether-thiolato ligands 32 and disulfide ligands [XC(S)S] 2 (X = NR 2 , OR (R = alkyl)) has previously been extensively investigated. 27,30b Since reactions of the thiuram disulfides with transition metal compounds may lead to the generation of dithiocarbamato (DTC) complexes, the analogous reactions of bis(allyl)Ru(IV) with dithiuram disulfides The previously reported literature method for the preparation of tpdt complexes of (HMB)Ru(II) 16 and Cp*Ru(III) 17 Figure 6) shows that the coordination geometry of complex 4 is very similar to that of its ruthenium analogue 17 with both dithiolato and thioether sulfur atoms coordinated simultaneously to the metal atom.…”