Trans-RuCl2

Hydrido-carbonyl and -phosphine complexes. Several new hydrido-diphenyl-phosphine complexes have been prepared from the recently described cis- or trans- [RuCl2(HPPh2)4] (Scheme 3). 

Zrara-[RuCl2(381-P,A, A, P )]. The complex trans- [RuCl2(380-P, N,N ,P )] catalyzes the hydrogenation of acrylic acid to propionic acid. " ... 

RuCl3(trpy) + PR3 + NEt3 - trans-[RuCl2(trpy)(PR3)] + Cl- + NEt3... 

The checkers obtained a 46% yield of trans-[RuCl2(trpyXPMej)], 2. 

Hydrogenation of 2,2,2-trifluoroacetophenone and its derivatives with a mixture of trans-RuCl2[(S)-xylbinap][(S)-daipen] and (CH3)3COK in 2-propanol gives the S alcohols quantitatively with a high optical purity (Scheme 1,64) [258]. Unlike with many chiral borane reagents [264], the sense of enantioface discrimination is the same as in hydrogenation of acetophenone. The electronic effects of 4 -substituents on the enantioselectivity are small. These chiral fluorinated alcohols are useful as components of new functionalized materials [265]. 

The vast majority of catalyst systems in Table 19.5 utilize ruthenium as a metal examples include trans-RuH -BHJfbinap l -diamine) (Ohkuma, 2002), trans-RuCl2[(R)-xylbinap][(R)-daipen] (Ohkuma, 2000b), and trans-RuCl2[P(C6H4-4-CH3)3]2(ethylenediamine) (Ohkuma, 2000a). 

Use of a BINAP/chiral diamine Ru complex trans- RuCl2[(R)-xylbinap][(R)-daipen] or the S,S complex efficiently catalyzes asymmetric hydrogenation of heteroaromatic ketones, with little influence of the ring properties on the enantioselectivity. Duloxetine, an inhibitor of serotonin and norepinephrine uptake carriers, has been synthesized in this way (Ohkuma, 2000b). 

Enantioface selection of prochiral diaryl ketones is generally difficult because electronically and sterically similar two aryl groups are attached to the carbonyl group. Overreduction of diaryl methanols to diaryl methanes is also another problem, but these problems are overcome by use of the Ru ternary catalyst system (Scheme 2.4b). Thus, by using (S,S)-20/KOC(CH3)3, 2-substituted benzophenones are quantitatively reduced to the diaryl methanols without any detectable diaryl methanes [102], With 3- or 4-substituted benzophenones, enantioselectivities are moderate. Benzoylferrocene is hydrogenated in the presence of trans-RuCl2 (S)-tol-binap (S)-daipen and a base to afford the S alcohol in 95% e.e. 

BINAP-Ru complexes show an excellent enantioselectivity in the hydrogenation of a-, /3-, or y-amino, -hydroxy, and -alkoxy ketones. Thus, a-dialkylamino ketones are effectively converted by (S)-BINAP-RuCl2 complexes to the chiral /3-amino alcohols with up to 99% e.e. (Eq. 2.25) [119, 120]. A normally unreactive Ru diacetate complex may be used for the hydrogenation of a-dimethylaminoacetone [119]. With a trans-RuCl2 (R)-xylbinap (R)-daipen ((R,R)-20)/KOC(CH3)3 catalyst system, a variety of a- and /3-amino ketones are hydrogenated in high optical yields [114]. Thus, a-(dimethylamino)acetone is converted to the S amino alcohol in 92% e.e. with an S/C of 2000 under 8 atm H2, whereas a-(dimethylamino)acetophenone is converted to the R alcohol in 93% e.e. with the same catalyst. The reversed sense of... 

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