Ferrocenylphosphines

For the synthesis of a related sulfur-containing ferrocenylphosphine catalyst see A. Togni. R. Htiuscl, Synlett 1990, 633. 

For the asymmetric hydrosilylation of 1,3-cyclohexadiene (42) (Scheme 3-17), the enantioselectivity is higher in the reaction with phenyldifluorosilane than that with trichlorosilane or methyidichlorosilane. The reaction of 42 with phenyldifluorosilane in the presence of a palladium catalyst coordinated with ferrocenylphosphine... 

Scheme 6.7 shows some other examples of enantioselective catalysts. Entry 1 illustrates the use of a Co(III) complex, with the chirality derived from the diamine ligand. Entry 2 is a silver-catalyzed cycloaddition involving generation of an azome-thine ylide. The ferrocenylphosphine groups provide a chiral environment by coordination of the catalytic Ag+ ion. Entries 3 and 4 show typical Lewis acid catalysts in reactions in which nitrones are the electrophilic component. 

Figure 27 The protection of the phosphorus lone pair during ROP of a phosphorus(III)-bridged [ljferrocenophanes by BC13 (380) or BH3 (38 H), leading to the production of the poly(ferrocenylphosphines) 39C1 and 39H, respectively. (Adapted from ref. 60.)...

The gold(I) complex of a chiral ferrocenylphosphine complex promotes asymmetric aldol reactions of a-isocyanocarboxylates to form chiral oxazolines in high diastereo- and enantio-selectivities (Scheme 52).225,226 In these reactions, the analogous silver(I) ferrocenylphosphine complex also works well. 

This alkylation reaction can be applied to intramolecular alkylation affording cyclic products, as shown in Equations (19)-(21). The reaction of 2-vinylpyridines with 1,5- or 1,6-dienes results in the formation of five- or six-membered carbocycles with good efficiency.20,20a,20b In addition to pyridine functionality, oxozole and imidazole rings can be applied to this intramolecular cyclization. When the reaction is conducted in the presence of a monodentate chiral ferrocenylphosphine and [RhCl(coe)2]2, enantiomerically enriched carbocycles are obtained. A similar type of intramolecular cyclization is applied to TV-heterocycles. The microwave irradiation strongly... 

In the asymmetric hydrosilylation of 1,3-cyclohexadiene 38 (Scheme 10, Table 4), catalyzed by chiral ferrocenylphosphines 5 and 40, the enantioselectivity is higher with phenyldifluorosilane than that with trichlorosilane or methyldichlorosilane (entries 1—4). The reaction of 38 with phenyldifluorosilane in the presence of a palladium catalyst coordinated with ferrocenylphosphine 40b gave allylsilane (A)-39c with 77% ee.58,59 The use of (j3-N-sulfonylaminoalkyl (phosphine 35a for the reaction of 38 with methyldichlorosilane exhibited the same level of asymmetric induction (entries 5-6).53 In this asymmetric hydrosilylation, combination of trichlorosilane and... 

Asymmetric Aldol Reactions with a Chiral Ferrocenylphosphine-Gold( I) Complex... 

TABLE 6-1. Asymmetric Hydrogenation of Trisubstituted Acrylic Acids Catalyzed by Chiral Ferrocenylphosphine-Rhodium Complexes... 

Asymmetric Synthesis Catalyzed by Chiral Ferrocenylphosphine Complex... 

Asymmetric aldol reaction. In the presence of a gold(I) complex (1) and a chiral ferrocenylphosphine (2), various aldehydes react with methyl isocyanoacetate... 

Asymmetric hydrogenation of a,fi-unsa turated acids.1 2- Aryl-3-methyl-2-bu-tenoic acids (2) undergo highly stereoselective hydrogenation catalyzed by a complex of rhodium with the chiral (aminoalkyl)ferrocenylphosphine (1), but not with... 

A combination of RuH2(PPh3)4 and ferrocenylphosphines catalyzes the crosscoupling reaction of a-hydroxyallenes and 1-alkynes to give exo-enynes selectively (Scheme 16.96) [102]. From the observation that O-protected allenes and 5-phenyl-1,2-pentadiene are inert to the cross-coupling reaction, the a-hydroxyl group in allenes plays an important role in this exo-selective reaction. 

Ferrocenylphosphines and their oxides (3) have been prepared by standard routes,7 and the properties of diferrocenylphosphine oxide (3 n = 2) reported.8 Derivatives of diphenyl(ferrocenylmethyl)phosphine oxide (4) have been prepared by a metallation-alkylation sequence,9 as shown for the oxide (5). 

Further investigations are needed to establish, whether this approach is really useful to obtain chiral allylsilanes 2, which are synthetically quite interesting intermediates. They are available otherwise only by asymmetric cross-coupling of silyl alkyl Grignard reagents with bromoethylenes in the presence of a chiral ferrocenylphosphine-palladium catalyst54. 

The ferrocenylphosphine complexes have also been widely used for the catalytic coupling reactions of a-phenylethyl reagents (see Table 1). 

Besides a considerable number of chiral Wilkinson-catalysts prepared from chiral a-hydroxy acids 33), carbohydrates 34), stereoids 35), and ferrocenylphosphines 36), many functionalized chiral hiphosphanes based on amino acids have also been developed. The first optically active tertiary phosphane was synthesized in 1961 by Horner et al.37). 

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