Nickel catalysts asymmetric reactions

Asymmetric hydrovinylation has been pioneered by Bogdanovic [30] and Wilke [31] using nickel catalysts. Of special interest is the reaction between vinylarenes and ethylene, as enantioselective codimerization provides a convenient route to... 

The ferrocenylphosphine-nickel catalysts are also applied to asymmetric synthesis of axially chiral biaryl compounds through the cross-coupling reaction. Although initial attempts to this... 

The other primary application of asymmetric Grignard coupling reactions has been in the synthesis of axially chiral binaphthyl and biphenyl derivatives. Hayashi performed a binaphthyl synthesis (equation 6) in 95% ee using a nickel catalyst and ligand (7), a P-O chelating analog to (3). For a similar synthesis of chiral biaryls (equation 7) ligand, (8) was found to yield the most successful results (93% ee). ... 

Optically active l,l -binaphthols are among the most important chiral ligands of a variety of metal species. Binaphthol-aluminum complexes have been used as chiral Lewis acid catalysts. The l,T-binaphthyl-based chiral ligands owe their success in a variety of asymmetric reactions to the chiral cavity they create around the metal center [107,108]. In contrast with the wide use of these binaphthyls, the polymer-supported variety has been less popular. The optically active and sterically regular poly(l,l -bi-naphthyls) 96 have been prepared by nickel-catalyzed dehalogenating polycondensation of dibromide monomer 95 (Sch. 7) [109] and used to prepare the polybinaphthyl aluminum(III) catalyst 97 this had much greater catalytic activity than the corresponding monomeric catalyst when used in the Mukaiyama aldol reaction (Eq. 29). Unfortunately no enantioselectivity was observed in the aldol reaction. 

Similar to nickel catalysts, palladium complexes that have a chiral phosphine ligand enable asymmetric-coupling reactions of secondary-alkyl Grignard reagents and organic halides [246,256,257]. A study giving excellent e.e.s was selected [Eq. (173) 408] from relevant works [359,363,369]. 

Asymmetric modifications of hydrovinylation are one of the earliest examples of successful asymmetric transition metal catalysis. After optimization of various dimerization and codimerization reactions using phosphane modified nickel catalysts, the first examples of asymmetric olefin codimerization were reported with n-allylnickel halides activated by organoaluminum chloride and modified by chiral phosphanes7. Thus, codimerization of 2-butene with propene using n-allylnickel chloride/A]X, (X = Cl, Br) in the presence of tris(myrtanyl)phosphane gives low yields of (—)-( )-4-methy 1-2-hexene (I) with 3% ee7,7 . 

A closely related asymmetric reaction is the nickel catalysed conjugate addition of dialkylzincs to Michael acceptors such as chalcone. Here, ACTC 63 showed the best performance [45]. A catalyst loading of 5 mol% of nickel salt was sufficient, albeit a high ligand loading of 50 mol% was necessary in order to suppress catalysis by achiral species, and the product was obtained in 90% chemical yield and with an enantiomeric excess of 62%, Scheme 12. 

Tai, A. (2002) Asymmetrically modified nickel catalyst (MNi) a heterogeneous catalyst for the enantio-differentiating hydrogenation, Murray Raney plenary lecture in Chemical Industries Series Catalysis of organic reactions) (Dekker), Morrell D.G. (ed.). 

Ozaki, H., Tai, A., Kobatake, S., Watanabe, H., and Izumi, Y. (1978) Enantioface-differentiating (asymmetric) hydrogenation of ketoester with modified Raney nickel catalyst (MRNi). XXXI. A comparative study of reaction rates and optical yields. Bull. Chem. Soc. Jpn. 51, 3559- 3563. 

Bartok, M., Wittmann, G.W., Gondos, G., and Smith, G.V. (1987) Homogeneous and heterogeneous catalytic asymmetric reactions. I. As5mimetric hydrogenation of the prochiral C=C bond on a modified Raney nickel catalyst, J. Org. Chem. 52, 1139 -1141. 

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