Ketoesters asymmetric hydrogenation

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 . 

The asymmetric hydrogenation with BisP RuBr2 may be applied to a wide range of (3-ketoesters, (3-kctoamidcs, and (3-ketophosphonates. Table 9.2 shows typical examples. 

The previous volume of Organic Syntheses provides a detailed procedure for the asymmetric hydrogenation of p-ketoesters using a BINAP-ruthenium complex.15... 

Ci-TunePhos-modified Pd catalysts have found applications in allylic asymmetric alkylations, asymmetric hydrogenations of a- and /3-ketoesters <2006SL1169, 2000JOC6223>, allylphthalimides <2005AGE4933>, enol acetates <2002OL4495>, and asymmetric cycloadditions <2005TL8213>. 

The first transition metal catalysis using BINAP-ruthenium complex in homogeneous phase for enantioselective hydrogenation of P-ketoesters was developed by Noyori and co-workers [31]. Genet and co-workers described a general synthesis of chiral diphosphine ruthenium(II) catalysts from commercially available (COD)Ru(2-methylallyl)2 [32]. These complexes preformed or prepared in situ have been found to be very efficient homogeneous catalysts for asymmetric hydrogenation of various substrates such as P-ketoesters at atmospheric pressure and at room temperature [33]. 

Dynamic kinetic resolution is well known in pure chemical synthesis, as illustrated by work by Noyori et al. on the asymmetric hydrogenation of a-substituted /f-ketoesters. Noyori et al. [5], Ward [6] and Caddick et al. [7] have reviewed the chemical syntheses, and biocatalytic routes have been discussed by Faber et al. [8]. 

S R ratio = 5 1) [22]. Yanada and Yoneda constructed the deazaflavinophane 26, which exhibits complete facial selectivity in its oxidation and reduction reactions, e.g. the reduction with NaBD to afford 27 [23], Belokon and Rozen-berg used scalemic 4-formyl-5-hydroxy[2.2]para-cyclophane (FHPC) 28 in the synthesis of a-ami-no acids (ee 45-98 %) [24], An alternative approach to FHPC was more recently reported by Hopf [25]. Other interesting advances in the area of chiral cyclophanes include the homochir-al [2.2]paracyclophane-derived amino acids 29 and 30 [26], as well as (5)-PHANEPHOS (31) [27], which has been shown to be an effective ligand for highly enantioselective Ru-catalyzed asymmetric hydrogenations of -ketoesters and... 

Asymmetric reduction The ruthenium(II)-BINAP catalysts developed by Noyori s group in 1980s were the most successful for the asymmetric hydrogenation of functionalized ketones such as a-ketoesters, a-hydroxyketones and a-aminoketones because the second... 

The catalyst lr-(R)-28a also showed good performance in the asymmetric hydrogenation of P-aryl p-ketoesters with excellent enantioselecfivity (up to 99.8% ee) and extremely high TONs (as high as 1 230 000) under mild reaction conditions (Scheme 17) [68]. 

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