Ferrocenylphosphine ligands

An asymmetric preparation of alkenylcyclopropanes has also been realized by the use of palladium(O) complexes carrying chiral ferrocenylphosphine ligands (equation 22)38. The requisite rt-allyl palladium intermediates can also be generated from allene and meth-ylenecyclopropane derivatives, 1839 and 1940, in the presence of palladium(O) complex and alkenyl or aryl halide (equations 23 and 24). The cobalt complexes, 20, similarly afford the corresponding alkenylcyclopropanes upon exposure to LDA (equation 25)41. 

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... 

Pastor and Togni pointed out that the central chirality and the planar chirality in the ferrocenylphosphine ligand 2 are cooperative for stereoselection (the concept of internal cooperativity of chirality) [16,23,24]. As Table 8B1.7 shows, the change of chirality of the stereogenic carbon atom from R to, S results in the formation of the other trans-oxazoline enantiomer with moderate enantiomeric excess. 

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]. 

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. 

Pd-catalyzed aryl etherifications to yield dihydrobenzofurans have been achieved by Hartwig and co-workers using bulky ferrocenylphosphine ligands (Equation 135) <2000JA10718> and by Buchwald and co-workers using bulky electron-rich o-biarylphosphine ligands <2000JA12907>. 

Illuminated by these promising results, several new chiral ferrocenylphosphine ligands were thus prepared. ° ° The enantioselectivity of the bicycloannulation... 

He, X. C. Wang, B. Yu, G. L. Bai, D. L. Studies on the asymmetric synthesis of huperzine A. Part 2 highly enantioselective palladium-catalyzed bicycloannulation of the beta-keto-ester using new chiral ferrocenylphosphine ligands. Tetrahedron-Asymmetry, 2001, 12(23) 3213-3216. 

Asymmetric Catalysis with Chiral Ferrocenylphosphine Ligands... 

Catalytic Asymmetric Reactions with Chiral Ferrocenylphosphine Ligands 113... 

The asymmetric cross-coupling of 1-phenylethylmagnesium chloride 20a with vinyl bromide 21 a has been reported by Hayashi and Kumada to proceed in the presence of 0.5 or 1 mol% of nickel or palladium catalyst coordinated with a chiral ferrocenylphosphine ligand to give optically active 3-phenyl-1-butene 22 [28]. 

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