Catalysts asymmetric hydrogenation using

Fig. 1. P MAS NMR spectrum of (a)Ru-BrNAP/PTA/y-Al203, and (b)Ru-BINAP crt rlex In order to find the characteristics of the immobilized catalyst, asymmetric hydrogenation of the prochiral C=C bond was performed as a model reaction. Firstly, three different homogeneous Ru-BINAP complexes including [RuCl2((R)-BINAP)], [RuCl((R)-BINAP)(p-cymene)]Cl and [RuCl((R)-BINAP)(Benzene)]Cl were immobilized on the PTA-modified alumina. Reaction test of immobilized catalysts showed that [RuCl2((R)-BINAP)] was the most active and selective so all the experiment were done using this catalyst afterwards.

Another hypothesis on homochirality involves interaction of biomolecules with minerals, either at rock surfaces or at the sea bottom thus, adsorption processes of biomolecules at chiral mineral surfaces have been studied. Klabunovskii and Thiemann (2000) used a large selection of analytical data, provided by other authors, to study whether natural, optically active quartz could have played a role in the emergence of optical activity on the primeval Earth. Some researchers consider it possible that enantioselective adsorption by one of the quartz species (L or D) could have led to the homochirality of biomolecules. Asymmetric adsorption at enantiomor-phic quartz crystals has been detected L-quartz preferentially adsorbs L-alanine. Asymmetrical hydrogenation using d- or L-quartz as active catalysts is also possible. However, if the information in a large number of publications is averaged out, as Klabunovskii and Thiemann could show, there is no clear preference in nature for one of the two enantiomorphic quartz structures. It is possible that rhomobohedral... 

This appears to be the first asymmetric hydrogenation using a solvent as the hydrogen source. Closely related to this is the use of the ruthenium(II) catalysts Ru2C14(DIOP)3 (Section III,B) or RuCl2P3, where P is a chiral... 

To our knowledge, there is to date only one report concerning asymmetric hydrogenation using a SILP catalyst [117]. Methyl acetoacetate was hydrogenated using Ru-BINAP dissolved in [BMIM][PF6] and immobilized on the poly(diallyl-dimethy-lammonium chloride) support (Fig. 41.14). 

Allylic alcohol derivatives are quite useful in organic synthesis, so the asymmetric synthesis of such compounds via asymmetric hydrogenation of dienyl (especially enynyl) esters is desirable. The olefin functionality preserves diverse synthetic potential by either direct or remote functionalization. Boaz33 reported that enynyl ester and dienyl ester were preferred substrates for asymmetric hydrogenation using Rh-(Me-DuPhos) catalyst [Rh(I)-(R,R)-14], and products with extremely high enantioselectivity (>97%) were obtained (Schemes 6-11 and 6-12). 

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]. 

Asymmetric hydrogenation using a metal catalyst [Ru((S)-BiNAP)].. .. 117... 

Ultimately, an alternative route based on asymmetric hydrogenation using a rhodium catalyst employing the Josiphos ligand was identified, but only demonstrated on a 10 g scale before the project was terminated (Scheme 1.37). " ... 

The group of Roelens published an organic pathway to substituted p-lactones from achiral p-carbonylesters via asymmetric hydrogenation using (/ )-BINAP-Ru (II) as catalyst yielding p-lactones with an ee of 97% [110] (Fig. 38). 

In the heterocyclic series several heteroarylalanines have been obtained by asymmetric hydrogenation using chiral homogeneous catalysts. For example, replacement of the phenyl ring by furan, thiophene, selenophene, pyridine, or indole yields fiirylalanines, thienyManines, 2- and 3-selenienyManines,... 

The present asymmetric hydrogenation using PhTRAP-rhodium catalyst is applicable to the syntheses of various optically active indolines possessing a substituent at... 

Harada, K., Yoshida, T. Asymmetric Hydrogenation Using Modified Cellulose-Palladium Catalysts. Naturwissenschaften 57, 131 (1970). 

Hydroxyalkylphosphonates have been prepared by reduction of the corresponding ketones. These include phosphonomalate esters by highly diastereose-lective reduction of 3-phosphonopyruvates with NHs.BHa and both 2-hydroxyalkyl-phosphonates, e.g. 178, and thiophosphonates by asymmetric hydrogenation using chiral ruthenium catalysts. An enantioselective synthesis, from 179, of both enantiomers of phosphonothrixin 180 and their absolute stereochemistry have been reported.The epoxide 179 was prepared from 2-methy -3-hydroxymethyl-1,3-butadiene via a Sharpless epoxidation. 

Asymmetric hydrogenation using modified solid metal catalysts is currently a topic under intensive research and development. In this respect, not only the reaction mechanism is studied, novel organic additives leading to more effective asymmetric hydrogenation are under consideration as well. ... 

Since tlie first successful report on heterogeneous asymmetric hydrogenation using inorganic materials by Kinting et al. in 1985 [22], numerous advances have been made in this area of research. Some representative examples of chiral reduction catalysts immobilized on inorganic support are summarized in Table 2.1. As... 

This section will review some latest developments in the area of asymmetric hydrogenation using supported metal catalysts. It will not cover homogeneous or biocatalysis. The field has been extensively reviewed by Blaser and Muller... 

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