Ferrocenylphosphines reactions

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. 

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... 

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

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. 

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

In 1986 Ito, Sawamura, and Hayashi [4] reported that gold(I) complexes prepared from cationic gold complex 1 and chiral ferrocenylphosphine ligands (2) bearing a tertiary amino group at the terminal position of a pendant chain are effective catalysts for asymmetric aldol reaction of... 

Recently it has been found that high stereoselectivity in the asymmetric aldol reaction of an isocyanoacetate is also obtainable with the silver catalyst containing ferrocenylphosphine ligands 2e, by keeping the isocyanoacetate concentration low throughout the reaction by the slow addition of 3a over a period of 1 h (Scheme 8B1.7, Table 8B1.8) [25]. 

Among chiral phosphine ligands used for the nickel- or palladium-catalyzed asymmetric cross-coupling, a series of the ferrocenylphosphines has shown a great success in terms of enantioselectivity and a variety of modified chiral ferrocenylphosphines has been applied to the reaction (10-16). The first example of asymmetric cross-coupling catalyzed by... 

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... 

Asymmetric hydrosilylation of cyclopentadiene with HSiCl3 catalyzed by a Pd complex of (Sj-f/ -ferrocenylphosphine (240, Rf = C3F7) proceeds in a 1,4-manner to give 3-silyl-1-cyclopentene (239, X = Cl) with up to 60% ee (R) (equation 93)246. The same reaction using (5,)-2-(A-methanesulfonylamino)-3-methyl-l-diphenylphosphinobutane (241) and HSiMeCF yields 239 (X = Me) with up to 71% ee (S) (equation 93)245. In a similar manner, the reaction of 1,3-cyclohexadiene with HSiF2Ph catalyzed by (/ )-(5 )-l-diphenylphosphino-2-(l-acetoxyethyl)ferrocene (PPF-OAc) affords (,S )-3-silyl-l-cyclohexene (242) with 77% ee (equation 94)247. 

Ferrocenylphosphines, chiral. Hayashi et al.1 have prepared a large number of chiral ferrocenylophosphines, which have planar chirality owing to 1,2-unsymmetrical substitution on the ferrocene group. In addition, one of the substituents contains a chiral carbon atom. The most interesting phosphines have amino or hydroxyl groups in the side chain. These phosphines, in combination with transition metals, can promote highly efficient enantioselective reactions. 

The same reaction conditions as above (2 mol% Pd, P Pd 1 4) were employed in the enantioselective allylation of 3-acetoxy-l,3-diphenylprop-l-ene in [C4Ciim][PF6], using ferrocenylphosphine ligands.1 331 Relative to the reaction in THF, the ee increased from 40% to 68% in the ionic liquid. After extraction of the product with toluene, reuse of the catalyst was possible, however both yield and selectivity decreased. 

A large fraction of the catalysts investigated for this purpose is on the basis of palladium or nickel complexes with chiral ferrocenylphosphine derivatives. This interest was spurred by the early work of Hayashi and Kumada who achieved the asymmetric coupling depicted in equation (5) (R = H) in 68% ee using phosphine (3) to provide chirality at the catalytic center. More recently, Knochel synthesized bisphosphine derivative (4) (R = Ph) which gave results similar to (3) when vinyl bromide was the substrate (equation 5, R = H, 63% ee). However, when the reaction was performed with /3-bromostyrene (R = Ph), the enantioselectivity see Enantioselectivity) increased to 93%. 

Kumada et al. have examined a number of chiral ferrocenylphosphines as ligands for asymmetric reactions catalyzed by transition metals. They are of interest because they contain a planar element of chirality as well as an asymmetric carbon atom. They were first used in combination with rhodium catalysts for asymmetric hydrosilylation of ketones with di- and trialkylsilanes in moderate optical yields (5-50%). High stereoselectivity was observed in the hydrogenation of a-acetamidoacrylic acids (equation 1) with rhodium catalysts and ferrocenylphosphines. ... 

Since generation of the intermediate ir-allylpalladium complex from allyl carbonates 3 b occurs with concomitant formation of the base ethoxide via decarboxylation of the leaving group, neutral di-tm-butyl iminodicarbonate can be used. The palladium(0)-catalyzed reactions of 3b with this nucleophile in the presence of ferrocenylphosphine (7 ,p5)-A are less efficient than the corresponding reaction of ( )-3b with benzylamine (see Table 9) in terms of enantiomeric excess, as well as chemical yield61. 

As exemplified by the enantioselective palladium(0)-catalyzed reactions of acyclic dicarbamates 4 a and b, cyclizations to 2-oxazolidinones 5 can be achieved with enantiomeric excesses of up to 77% in the presence of ferrocenylphosphine (/ ,pS)-A63. Since (S)-5a of nearly the same enantiomeric excess is obtained from both (E)- and (Z)-4a, epimerization of the intermediate Ti-allylpalladium complexes is fast compared with nucleophilic attack. Remarkably, cyclization of ( >4a proceeds with lower stereoselectivity at lower reaction temperatures. After recrystallization of (S)-5b (70 % ee), essentially enantiomerically pure (Aj-Sb (>97% ee) is obtained, which has been readily hydrolyzed to (S )-2-amino-3-buten-l-ol. 

Using ferrocenylphosphine (R.p.S )-A, (S)-5 a is also available by a palladium(0)-catalyzed reaction of racemic vinyl epoxide 6 with phenyl isocyanate63 (see Section 7.4.1.2.), albeit with lower enantioselectivity than from 4 a. 

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