Ru -catalysed asymmetric

The seven-membered ring containing chiral bisphosphine 121 (n = 1) was made as part of a series of bisphosphines (n = 1-6) to study the influence of ligand dihedral angles on the enantioselectivity of Ru-catalysed asymmetric hydrogenation of p-ketoesters . 

Copolymer of PEG, (R)- =0.05 H20SMe0H =, Ru-catalysed asymmetric Precipitation (ether) [145]... 

Copolymer of PEG, (R)-5,5 -diamino-BINAP, and terephthaloyl chloride =0.05 H20 ,Me0H =, ethylene glycol", Et0Ac/H20" Ru-catalysed asymmetric hydrogenation of a,p unsaturated carhoxyhc acids (-t) Precipitation (ether) [145]... 

Ru-catalysed asymmetric hydrogenation of unsaturated carboxylic acids... 

Scheme 14.2 Application of Ru-catalysed asymmetric hydrogenation to (i )-citronellol. ...

In 2004, ruthenium-catalysed asymmetric cyclopropanations of styrene derivatives with diazoesters were also performed by Masson et al., using chiral 2,6-bis(thiazolines)pyridines. These ligands were prepared from dithioesters and commercially available enantiopure 2-aminoalcohols. When the cyclopropanation of styrene with diazoethylacetate was performed with these ligands in the presence of ruthenium, enantioselectivities of up to 85% ee were obtained (Scheme 6.6). The scope of this methodology was extended to various styrene derivatives and to isopropyl diazomethylphosphonate with good yields and enantioselectivities. The comparative evaluation of enantiocontrol for cyclopropanation of styrene with chiral ruthenium-bis(oxazolines), Ru-Pybox, and chiral ruthenium-bis(thiazolines), Ru-thia-Pybox, have shown many similarities with, in some cases, good enantiomeric excesses. The modification... 

The broad range of alkenes undergoing asymmetric hydrogenation using ruthenium-based systems as catalysts has attracted the attention of chemists engaged in the synthesis of chiral biologically active natural products (Scheme 13)[60] and other pharmaceuticals (Scheme 14)[61]. a, (3-Unsaturated phosphoric acids and esters have also proved to be suitable substrates for Ru(II)-catalysed asymmetric hydrogenation [62]. 

Epoxidation reactions are important because epoxides are useful intermediates -ring opening allows subsequent reactions at one or both of the carbon atoms, and this is particularly attractive if asymmetric epoxidations can be accomplished (3.1.1.3). This is an increasingly important area for Ru-catalysed oxidations, and a review [2] emphasises in particular mechanistic aspects of such processes. There are also earlier brief reviews of the topic [4, 7,18], in particular by porphyrin-based systems [17-22],... 

Ferrocene-based aminophosphines are shown to be effective ligands in the Ru(II)- catalysed asymmetric hydrogenation of ketones. The enantioselectivity is mainly determined by the C-centred chirality of the ligands, but the planar chirality is also important, and (Rc,SFc)- or (Sc,Rfc)- is the matched combination of chiralities.334 Dimethyl oxalate is selectively hydrogenated to methyl glycolate with Ru(acac)3,... 

A class of simple, modular, and highly efficient a-amino acid amides ligands for Ru-and Rh-catalysed asymmetric transfer hydrogenation of aromatic ketones in propan-2-ol has been developed. A remarkable feature with these ligands is the switch of product enantioselectivity observed when the amide functionality is replaced by the corresponding thioamide. The results obtained have significant mechanistic implications... 

Asymmetric hydrogen transfer from 2-propanol to aromatic ketones such as acetophenone (99) has been achieved by using the same chiral Ru complex in 2-propanol containing KOH at room temperature, and (S)-1 -phenylethanol (100) with 98% ee was obtained [68,69]. Similarly, efficient Ru-catalysed transfer hydrogenation of aromatic ketones using the cyclic amino alcohol [(I. S, 3R,4i )-2-azanorbomylmetha-nol] (110) [70] and bis(oxazolinylmethyl) amine (111) [71] was reported. 

This revolution in asymmetric catalysis using chiral complexes of transition metals was made possible principally by the work of Ryoji Noyori (who developed the Ru- and Rh-catalysed reductions we describe in this chapter) and of K. Barry Sharpless (who developed the Os- and Ti-catalysed oxidations). This work won Noyori and Sharpless the Nobel Prize for Chemistry in 2001, along with William Knowles (who was the first to apply metal-catalysed asymmetric reactions to industrial targets). 

The complex Ru( -methallyl)2(cod)-PhTRAP [using (R,R)-(5, 5)-PhTRAP (220) and (5,S)-(R,R)-PhTRAP (221)] catalysed asymmetric hydrogenation of the substituted imidazoles and oxazoles into the corresponding chiral imidazolines and oxazolines, respectively. The optically active products (up to 99% ee) could be converted to chiral... 

The scope of the ruthenium-catalysed asymmetric transfer hydrogenation methodology was very recently extended to a-alkyl-substituted )S-ketoamides by Limanto et Indeed, the first enantio- and diastereoselective synthesis of various syn a-alkyl-substituted jS-hydroxyamides via highly efficient Ru-cata-lysed hydrogenation through DKR of the corresponding ) -ketoamides has been successfully demonstrated. As shown in Scheme 2.31, excellent diastereo-and enantioselectivities of up to 98% de and > 99% ee, respectively, were observed when the process was performed in CH2CI2 or toluene as the solvent. 

---