Ru complexes with

The reactions of the butadiynediyldimetal(Fe, Ru) complexes with Fe2(CO)ci at room temperature afforded mixtures of products, from which three types of products, viz. the ps-acetylide cluster compound 4, the pj-ti -propargylidene-ketene compound 5 and zwitterionic cluster compound 6, were isolated. While the reaction with an excess amount of Co2(CO)g results in addition to the sterically congested Fp -C=C part [6]. The distributions of the products were dependent on the metal fragments situated at the other end of the conjugated carbon rod. The cluster compounds so obtained were characterized by spectroscopic and... 

Norton and coworkers found that catalytic enantioselective hydrogenation of the C=N bond of iminium cations can be accomplished using a series of Ru complexes with chiral diphosphine ligands such as Chiraphos and Norphos [68], Even tetra-alkyl-substituted iminium cations can be hydrogenated by this method. These reactions were carried out with 2 mol.% Ru catalyst and 3.4—3.8 bar H2 at room temperature in CH2C12 solvent (Eq. (39)). 

Fig. 32.46 Hydrogenation of racemic 2-substituted cyclohexanones through dynamic kinetic resolution catalyzed by BINAP/chiral diamine-Ru complexes with base.

The hydrogenation of allylic alcohols and a,/>-unsaluraled acids leads to products with a very high synthetic potential, and both transformations were used quite early for industrial applications. In both cases Ru complexes with axially chiral biaryl ligands (binap analogues) are the catalysts of choice. Here, we will dis-... 

Crude BINAP-Ru complex with consistent spectral characteristics can be used for hydrogenation of geraniol (98.7% pure commercial geraniol containing 1.3% of nerol, distilled from 4 A molecular sieves, 4.7 M substrate in 95% aqueous methanol, 2.8 mM Ru(OCOCH3)2[(R)-BINAP], 100 atm of H2, 20°C, 8 hr), to give (S)-citronellol in 96% ee, 97% isolated yield. 

Cyclopropanation is an important synthetic method, and enantioselective catalytic reactions of olefins and diazoacetates provide access to valuable products with biological activity. In general, these reactions are conducted in anhydrous solvents and in several cases water was found to diminish the rate or selectivity (or both) of a given process. Therefore it came as a surprise, that the Cyclopropanation of styrene with (+)- or (-)-menthyl diazoacetates, catalyzed by a water-soluble Ru-complex with a chiral bis(hydroxymethyldihydrooxazolyl)pyridine (hm-pybox) ligand proceeded not only faster but with much Wgher enantioselectivity (up to 97 % e.e.) than the analogous reactions in neat THF or toluene(8-28 % e.e.) (Scheme 6.34) [72]. The fine yields and enantioselectivities may be the results of an accidental favourable match of the steric and electronic properties of hm-pybox and those of the menthyl-dizaoacetates, since the hydroxyethyl or isopropyl derivatives of the ligand proved to be inferior to the hydroxymethyl compound. Nevertheless, this is the first catalytic aqueous cyclopropanation which may open the way to other similar reactions in aqueous media. 

Figure 1.16 lists other chiral ligands useful for asymmetric hydrogenation of ot-and/or p-keto esters.A Ru complex with BPE, a fully alkylated diphosphine. 

Structures and reactivities of Ru complexes with EDTA have been reviewed [628],... 

A Ru complex with a chiral oxazolinylferrocenylphosphine (S)-6 (substrate Ru=100 l) with Cu(0S02CF3)2 promoted hydrosilylation of acetophenone using diphenylsilane (2 equivalents) in ether at 0 °C to give (R)-l-phenylethanol in 95% ee and in 59% yield after hydrolysis (Scheme 16) [31]. Propiophenone was reduced with 97% optical yield. This complex was also effective for the hydrosilylation of 2-phenyl-l-pyrroline in toluene at 0 °C to afford the S chiral amine in 88% ee [31].RuCl2[(.R)-TolBINAP][(S)-7] and Ag0S02CF3 catalyzed the hydrosilylation of acetophenone (substrate Ru Ag=100 l 4) with diphenylsilane to give the R product in 82% ee [32,33]. 

Unlike the Rh-based hydrogenation of a-(acylamino)acrylates, the corresponding Ru chemistry has not been studied extensively. Ru complexes of (S)-BINAP and (S,S)-CHIRAPHOS catalyze the hydrogenation of (Z)-a-(acylamino)cinnamates to give the protected ( -phenylalanine with 92% ee [74] and 97% ee [75], respectively. It is interesting that the Rh and Ru complexes with the same chiral diphosphines exhibit an opposite sense of asymmetric induction (Scheme 1.6) [13,15,56,74,75]. This condition is due primarily to the difference in the mechanisms the Rh-catalyzed hydrogenation proceeds via Rh dihydride species [76], whereas the Ru-catalyzed reaction takes place via Ru monohydride intermediate [77]. The Rh-catalyzed reaction has been studied in more detail by kinetic measurement [78], isotope tracer experiments [79], NMR studies [80], and MO calculations [81]. The stereochemical outcome is understandable by considering the thermodynamic stability and reactivity of the catalyst-enamide complexes. 

Dihydrogeranylacetone, though not a completely simple olefin, is chemoselectively hydrogenated at the C=C bond in the presence of a Ru complex with MeO-BIPHEP analogue containing four P-2-fury 1 groups to afford the saturated ketone with 91 % ee (Scheme 1.31) [86]. Examples of hydrogenation of a trisubstituted olefin with an oxo or oxy substituent in the p-position are unknown. 

Rh and Ru complexes with electron-rich Tang-Phos and Duan-Phos catalyse a highly enantioselective hydrogenation of A-phthaloylenamides. In the hydrogenation of a-arylenamides, up to 99% ee has been achieved though a moderate ee is obtained in the reduction of a-alkylenamides 340... 

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