Asymmetric hydrogenation acetophenone

Ruthenium complexes of (129) and (130)336 were investigated for the asymmetric hydrogenation of prochiral 2-R-propenoic acids (Scheme 62a) rhodium complexes of these ligands were used for hydrogenation of acetoamido-cinnamic acid methyl ester (Scheme 62c) and hydrogenation of acetophenone-benzylamine (Scheme 62b). The results obtained with these... 

The cluster complex H4Ru4(CO)8(DIOP)2 has been used at 150°C with 100 atm H2 for asymmetric hydrogenation of acetophenone and methyl-... 

According to Chen et ah, alkali cation co-catalysis kinetics cannot be distinguished from classic ideas (proton instead of alkali) for the asymmetric hydrogenation of acetophenone with the Noyori-catalyst trans-RuC12[(S)-BINAP]... 

A chiral catalyst consisting of Irans-RuC]2(xy]binap)(daipen) and (CH3)3COK in 2-propanol effects asymmetric hydrogenation of a-, / -, and y-amino aromatic ketones [128]. Hydrogenation of 2-(dimethylamino)acetophenone catalyzed by the (R)-XylBINAP/(R)-DAIPEN-Ru complex [(R,R)-31D] gives the R amino alcohol in 93% ee (Fig. 32.36). The optical yield is increased up to 99.8%, when... 

In 1969, Fiaud and Kagan[U1 tested ephedrine boranes but achieved only 3.6-5% enantiomeric excess in the reduction of acetophenone. Itsuno et a/.[121 reported in 1981 an interesting enantioselective reduction of a ketone using an amino alcohol-borane complex as a catalyst. Buono[131 investigated and developed the reactivity of phosphorus compounds as ligands in borane complexes for asymmetric hydrogenation. 

Andersson reported the use of ligand 13a in the asymmetric hydrogenation of substituted acetophenone-based 77-aryl imines (Table 18) [88, 89]. New ligands 84 and 85 were reported by the groups of Bolm and Knochel, respectively, for... 

Iridium-Catalyzed Asymmetric Hydrogenation of Olefins with Chiral N,P and C,N Ligands 71 Table 18 Asymmetric hydrogenation of acetophenone based A-aryl ketimines... 

Table 4.4 Asymmetric hydrogenation of acetophenones using Ir complexes bearing planar chiral ferrocenyl phosphino thioethers. ...

Aromatic Ketones The DIOP-Rh [116] and DBPP-Rh [117] complexes, in conjunction with a tertiary amine, have been employed in the asymmetric hydrogenation of acetophenone, albeit with moderate enantioselectivity (80 and 82% respectively Tab. 1.10). The asymmetric hydrogenation of aromatic ketones was significantly improved by using the Me-PennPhos-Rh complex, with which enantioselectivities of up to 96% ee were achieved [36]. Interestingly, the additives 2,6-lutidine and potassium bromide were again found to be crucial for optimum selectivity, although their specific role has not been determined. 

Carbonyl groups are not reduced with classical Wilkinson catalysts. However, some cationic rhodium complexes show catalytic activity 52K There are only a few examples of asymmetric hydrogenation of ketones. Addition of base to a neutral rhodium complex is also a way to produce a catalyst for ketone reduction 44). Acetophenone... 

Pioneering studies on the asymmetric hydrogenation of a-amino ketones have been done by Kumada and Achiwa [3, 4]. Achiwa s MCCPM/Rh complex catalyzed the reaction of 2-(dimethylamino)acetophenone hydrochloride with an Si C of 100,000 under 20 atm of H2 to give the corresponding chiral amino alcohol in 96% ee [32], although the reactions of other amino ketones showed less satisfactory rates and enantioselectivity. 

Asymmetric hydrogen transfer from 2-propanol to aromatic ketones such as acetophenone (99) has been achieved by using the same chiral Ru complex in 2-propanol containing KOH at room temperature, and (S)-1 -phenylethanol (100) with 98% ee was obtained [68,69]. Similarly, efficient Ru-catalysed transfer hydrogenation of aromatic ketones using the cyclic amino alcohol [(I. S, 3R,4i )-2-azanorbomylmetha-nol] (110) [70] and bis(oxazolinylmethyl) amine (111) [71] was reported. 

Merck reported the synthesis and isolation of (7 )-3,5-bistrifluoromethylphenylethanol (170) in high yields and enantiomeric excess by asymmetric hydrogen transfer. Reduction of 3,5-bistrifluoro-acetophenone (128, Ar = 3,5-(CF3)2C6H3, R = Me) with catalyst 169, prepared in situ from [RuCl2(p-cymene)]2 and (I S,2R)-cA-l-aminoindan-2-ol, produced the chiral alcohol 170 in 91-93% ee (Scheme 12.67).213... 

In contrast to the number of intramolecular asymmetric hydrogen abstraction reactions using supramolecular approaches (Sec. IV.D.), intermolecular asymmetric hydrogen abstraction reactions have been scarcely reported. Only two examples are presented these occur in inclusion crystals of deoxycholic acid with ketones and crystals of cyclodextrin with acetophenone. 

Table 7.5 Rh-catalyzed asymmetric hydrogenation of acetophenone using rhodacarborane catalyst 17.

Zhu and coworkers [22] reported an asymmetric hydrogenation of aromatic ketones in the presence of a rhodacarborane-based chiral catalyst 17, which was derived from rhodacarborane precursor 16 and (R)-BINAP, in ionic liquids (Scheme 7.5). The hydrogenations of acetophenone in the presence ofthe catalyst precursor 16 and (R)-BINAP (0.001 0.0015 for acetophenone) were performed in the ionic liquid medium such as [omim][BF4], [brnim lh7,, or a new hquid salt comprised of 1-carbododecaborate ions and N-n-butylpyridinium (BP) ions, [BP][CB1XioHi2], and tetrahydrofuran (THF) at 50°C under H2 (12atm) for 12h. As shown in Table 7.5, the catalytic activities and enantioselectivities in ionic liquids (entries 1-3) were higher in comparison with those obtained in TH F (entry... 

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