Asymmetric hydrogenation homogeneous, reviews

A review of asymmetric hydrogenation of ketones with rhodium complexes as catalysts has been presented.330 A review of the developments in the asymmetric hydrogenation of ketones with ruthenium complexes as homogenous catalysts of hydrogenation, with particular emphasis on the work of Halpern, has been presented.331... 

For a review of homogeneous asymmetric hydrogenation, see V. Capiar, G. Comisso and V. Sunjic, Synthesis, 1981, 85. 

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... 

Interest in the chemistry of the 6ji-phosphinine (phosphabenzene) system has continued, although considerably fewer papers have appeared compared to recent years. The synthesis, coordination chemistry and catalytic applications of phosphi-nines have been reviewed." New chiral bidentate phosphinine ligands (220) have been prepared and their coordination chemistry and applications in rhodium-catalysed asymmetric hydrogenations assessed." The diphosphinine (221) continues to find new applications as a ligand in homogeneous catalysis" and a new mode of coordination to a metal has been identified for the phosphinine (222), two such ligands simultaneously bridging a Mn-Mn bond." ... 

The homogeneous hydrogenation and asymmetric hydrogenation of organic compounds catalysed by transition-metal complexes and salts have been reviewed. ... 

Good reviews of asymmetric homogeneous hydrogenation catalysts and their syntheses are those of Caplar et al. 28) and Vineyard et al. (106). 

Only a few other cobalt complexes of the type covered in this review (and therefore excluding, for example, the cobalt carbonyls) have been reported to act as catalysts for homogeneous hydrogenation. The complex Co(DMG)2 will catalyze the hydrogenation of benzil (PhCOCOPh) to benzoin (PhCHOHCOPh). When this reaction is carried out in the presence of quinine, the product shows optical activity. The degree of optical purity varies with the nature of the solvent and reaches a maximum of 61.5% in benzene. It was concluded that asymmetric synthesis occurred via the formation of an organocobalt complex in which quinine was coordinated in the trans position (133). Both Co(DMG)2 and cobalamin-cobalt(II) in methanol will catalyze the following reductive methylations ... 

In this chapter and in Chapters 10-12, we will review and validate some methods for asymmetric (transfer) hydrogenation of carbon-oxygen and carbon-carbon double bonds catalysed by non-metallic systems, homogeneous transition metal catalysts and biocatalysts. Reduction of carbon-nitrogen double bond systems will be reported in another volume of this series. 

The publication (70) in 1976 of the preparation of optically active epoxyketones via asymmetric catalysis marked the start of an increasingly popular field of study. When chalcones were treated with 30% hydrogen peroxide under (basic) phase-transfer conditions and the benzylammonium salt of quinine was used as the phase-transfer catalyst, the epoxyketones were produced with e.e. s up to 55%. Up to that time no optically active chalcone epoxides were known, while the importance of epoxides (arene oxides) in metabolic processes had just been discovered (71). The nonasymmetric reaction itself, known as the Weitz-Scheffer reaction under homogeneous conditions, has been reviewed by Berti (70). 

Review. Noyori has reviewed homogeneous asymmetric catalysis, particularly by complexes of (R)- and (S)-BINAP with ruthenium. He suggests possible reasons for the high efficiency of Ru-BINAP complexes in catalytic hydrogenation (40 references). 

In recent years there has been much interest in homogeneous hydrogenations catalyzed by transition metal complexes (7). One facet of research in this area is the search for chiral catalysts (catalysts that are dissymmetric, i.e., optically active) that can be used to produce chiral compounds via asymmetric reactions. In this review, we survey asymmetric homogeneous hydrogenation reactions, that is reactions that create asymmetric carbon atoms by the addition of hydrogen across multiple bonds under the influence of soluble chiral catalysts. 

A related feature is the ability of asymmetric complexes to induce chiral reactions, e.g., in catalytic hydrogenation (reviewed by Birch and Williamson, 1976). Asymmetric synthesis using homogeneous transition metal catalysts has recently been reviewed (Bogdanovii, 1973). 

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