Transition metal catalysis asymmetric reduction

As shown in Figure 1.26, a chiral Sm(III) complex catalyzes asymmetric reduction of aromatic ketones in 2-propanol with high enantioselectivity. Unlike other late-transition-metal catalysis, the hydrogen at C2 of 2-propanol directly migrates onto the carbonyl carbon of substrate via a six-membered transition state 26A, as seen in the Meerwein-Ponndorf-Verley reduction. ... 

Chiral alcohols, respectively hydroxy groups, are a common motive in natural products and bioactive compounds. Therefore, the asymmetric reduction of ketones is a frequently used procedure. In contrast to the asymmetric reduction of imines vide infra), only few organocatalytic methods to reduce ketones are known, and mostly transition metal catalysis or enzymatic methods are used. The... 

Asymmetric catalysis undertook a quantum leap with the discovery of ruthenium and rhodium catalysts based on the atropisomeric bisphosphine, BINAP (3a). These catalysts have displayed remarkable versatility and enantioselectivity in the asymmetric reduction and isomerization of a,P- and y-keto esters functionalized ketones allylic alcohols and amines oc,P-unsaturated carboxylic acids and enamides. Asymmetric transformation with these catalysts has been extensively studied and reviewed.81315 3536 The key feature of BINAP is the rigidity of the ligand during coordination on a transition metal center, which is critical during enantiofacial selection of the substrate by the catalyst. Several industrial processes currently use these technologies, whereas a number of other opportunities show potential for scale up. 

The asymmetric catalytic reduction of ketones (R2C=0) and imines (R2C=NR) with certain organohydrosilanes and transition-metal catalysts is named hydrosilylation and has been recognized as a versatile method providing optically active secondary alcohols and primary or secondary amines (Scheme 1) [1]. In this decade, high enantioselectivity over 90% has been realized by several catalytic systems [2,3]. Therefore the hydrosilylation can achieve a sufficient level to be a preparative method for the asymmetric reduction of double bond substrates. In addition, the manipulative feasibility of the catalytic hydrosilylation has played a major role as a probe reaction of asymmetric catalysis, so that the potential of newly designed chiral ligands and catalysts can be continuously scrutinized. 

Metal Catalysts describes a number of asymmetric catalytic reactions, while nucleophilic activation of carbon monoxide and the application of metal carbonyl catalyzed water-gas shift (WGS) and related reactions to homogeneous catalysis have also been reviewed. A review on transition metal catalyzed carbonylations covers the year 1986. Reductions using ammonium formate as the reducing agent in the presence of homogeneous and heterogeneous nickel and palladium catalysts have been the subject of a recent survey. 

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). 

Duml973 Dumont, W., Poulin, J.C., Dang, T.P. and Kagan, H.B., Asymmetric Catalytic Reduction with Transition Metal Complexes. II. Asymmetric Catalysis by a Supported Chiral Rhodium Complex, J. Am. Chem. Soc., 95 (1973) 8295-8299. 

Dumont W, Poulin JC, Dang TP, Kagan HB. Asymmetric catalytic reduction with transition metal complexes. II. Asymmetric catalysis by a supported chiral rhodium complex. J. Am. Chem. Soc. 1973 95(25) 8295-8299. 

This compilation embraces a wide variety of subjects, such as solid-phase and microwave stereoselective synthesis asymmetric phase-transfer asymmetric catalysis and application of chiral auxiliaries and microreactor technology stereoselective reduction and oxidation methods stereoselective additions cyclizations metatheses and different types of rearrangements asymmetric transition-metal-catalyzed, organocatalyzed, and biocatalytic reactions methods for the formation of carbon-heteroatom and heteroatom-heteroatom bonds like asymmetric hydroamina-tion and reductive amination, carboamination and alkylative cyclization, cycloadditions with carbon-heteroatom bond formation, and stereoselective halogenations and methods for the formation of carbon-sulfur and carbon-phosphorus bonds, asymmetric sulfoxidation, and so on. 

Chiral transition-metal complexes have also been featured in the following reports " of asymmetric carbonyl reductions hydrogenation of / -aryl- -ketoesters 0 using H2 and iridium-bearing spiro pyridine-aminophosphine ligand rhodium in a theoretical study of catalysis involving amino acid-derived ligands and in... 

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