Hydrogenation of methyl acetoacetate

Table 41.18 Homogeneous, biphasic and heterogeneous enantioselective hydrogenations of methyl acetoacetate with Ru-BINAP [117],...

Hydrogenation of methyl acetoacetate was successfully carried out in water catalyzed by a complex obtained in situ from [ RuCl2(benzene)2 2] + (/ 9-(+)BIFAPS (50) (Scheme 3.22). Spectacular effects of small amounts of added HCl or H2SO4 were found under comparable conditions the conversion increased from 58% to 100% and the e.e. from 22% to 86% [111]. The origin of this effect of acids is unclear it was speculated that... 

Ligand (349), water-soluble (350), and their (R)-enantiomers have been synthesized, and their Ru complexes used as catalysts (see also Section 5.5.3.2.5) for the asymmetric hydrogenation of methyl acetoacetate and (Z)-acetamidocinnamic acid. " The complex [Ru (5)-351 (OAc)2] and... 

Fig. 8. Effect of the modifier structure on the optical yield for the hydrogenation of methyl acetoacetate [4] and ethyl pyruvate [58],...

Comparisons in the asymmetric hydrogenation of methyl acetoacetate (111) with ruthenium catalysts that contain C2-Tunephos (110b) and 116 indicated an improvement in enantiomeric excess when the ether linkage contained additional chirality.134140... 

Later, the optical yields over the modified Raney Ni were greatly improved by hydrogenating the substrate in the presence of sodium bromide.210 Thus, the best optical yield of 88.6% ee was obtained in the hydrogenation of methyl acetoacetate over Raney Ni modified 3 times with tartaric acid in the presence of sodium bromide with addition of a small amount of acetic acid (eq. 5.48). 

A more specific interaction between a zeolite surface and a chiral catalyst was recently uncovered (58). It was found that the Ru-binap catalyst can be specifically withheld on the outer surface of Beta zeolites. Such a heterogeneous catalyst is relevant for the highly enantioselective hydrogenation of methyl acetoacetate to (R) or (S) 3-hydroxymethylbutyrate, with typical ee values of about 95 %. 

Asymmetric hydrogenation. Raney nickel that has been soaked at 100° in an aqueous solution of tartaric acid and sodium bromide can effect asymmetric hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate and of acetylacetone to 2,4-pentanediol/ In both cases optical yields near 90% can be achieved. 

Table 4 Hydrogenation of Methyl Acetoacetate over Raney Nickel Modified with Tartaric Acid-Inorganic Salt...

Although palladium on polypeptide sterns mentioned above are heterogei mis, homogeneous system may be realized by the complexation of ruthenium(III) ion to poly(S-glutamic acid), which was fwnd effective as catafyst for the asymmetric hydrogenation of methyl acetoacetate (Hirai, Aikawa, Fumta (7)). 

In connection with these studies, the a nunetric hydrogaiatkm catalyzed by Raney nickel modified with dipeptide ould be mentioned. In the hydrogenation of methyl acetoacetate [Eq. (5)], Izumi and his co-workers (JO) found that the... 

Keane MA, Webb G (1992) The enantioselective hydrogenation of methyl acetoacetate over supported nickel catalysts I. The modification procedure. 1 Catal 136 1 Keane MA (1997) Interaction of optically active tartaric acid with a nickel-sUica catalyst role of both the modification and reaction in determining enantioselectivity. Langmuir 13 41... 

Scheme 5.6 Hydrogenation of methyl acetoacetate (S) enantiomers of 21-23 were also tested.

Modified nickel catalysts were prepared from the various nickel sources (Table 1). In the case of the modified nickel catalysts prepared from NiO, e.d. ability of the catalyst depended on the NiO manufacturers. These phenomena were also observed for the e.d. hydrogenation of methyl acetoacetate (MAA) [6]. Since the method of the NiO preparation presumably affect the percentage of crystallite part of reduced Ni, the types of NiO would reflect the e.d. ability of the catalyst. On the other hand, fine nickel powder (FNiP) gave the e.d. catalyst... 

Hydrogenation of methyl acetoacetate was successfully carried out in water catalyzed by a complex obtained in situ from [ RuCl2(benzene)2 2] +... 

Izumi and Akabori first invented MNi in 1963. They modified freshly prepared Raney nickel (W-1 type) with a mono-sodium salt of glutamic acid (Gul-MRNi). This catalyst gave a 15% e.d.a. for the hydrogenation of methyl acetoacetate (MAA) to methyl 3-hydroxybutanoate (MHB). It was sheer luck that MAA was employed as the substrate. Even today MAA is one of the best substrates, and it has long been employed as a standard. Immediately after the discovery by Izumi et al, Klabunovskii and coworkers started studies of this type of catalyst, and the groups led by Izumi and Klabunovskii carried out almost all the early research. ... 

MA Keane. The role of catalyst activation in the enantioselective hydrogenation of methyl acetoacetate over silica-supported nickel catalysts. Can. J. Chem. 72 372-381, 1994. 

Modification Method Studies for the Preparation of Tartaric acid-NaBr-Modified Nickel Catalyst for the Enantio-differentiating Hydrogenation of Methyl Acetoacetate... 

Fig. 1 Enantio-differentiating hydrogenation of methyl acetoacetate. Modification solution tartaric acid (1.18 g) and NaBr (2 mg) in 118 cm of THF. Modification condition 0.1 MPa, 273 K, Ih. e.d.a., O conversion...

Fig. 1. Asymmetric hydrogenation of methyl acetoacetate catalyzed by ruthenium(III) complex with (7) ...

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