Aryl-ferrocenyl ligands

Zhou also reported a series of related P,S-ferrocenyl ligands and their use in the [3+2] cycloaddition of aryl-substituted azomethine ylides with A-phenylmalei-mide.52 While these silver complexes were able to efficiently catalyze the reaction, the enantioselectivity was lower than in the protocol described above. 

Excellent enantioselectivity and double-bond regioselectivity can be achieved in an asymmetric Heck reaction between 2,3-dihydrofuran and aryl triflates by using a combination of chiral diphosphine-oxazoline ferrocenyl ligand and Pd catalyst <03CEJ3073>, as shown below. Chiral diphosphine-containing (arene)tricarbonylchromium(O) complexes were also used as ligands for this reaction to obtain the 2,3-isomer, however, both the yield and enantioselectivity were modest <03TA1455>. 

A different solution to the use of hydrophilic ligands is possible for the Suzuki reaction of aryl bromides in water. The complex Pd(dppf)Cl2 (dppf = l,l -bis(diphenylphosphino)ferrocene, 102) was indeed an extremely active catalyst, simply using an aqueous solution of K2CO3 as the reaction medium. Excellent yields and TONs up to 870 000 were recorded for the reaction of l-bromo-4-nitrobenzene and phenylboronic acid at 110 °C for 48 h (Scheme 1.66). The choice of the ferrocenyl ligand in Pd(dppf)Cl2, a weakly electron-... 

Tosylates are not reactive partners of amination. Even P(t-Bu)3 is not effective. Buchwald reported that amination of tosylates and benzene sulfonates with various amines proceeded smoothly by using biphenyl-based phosphine IV-17 in the presence of CS2CO3 [21a], Bidentate ferrocenyl ligands, Dt-BPF (XI-4), XI-9, and XI-10 are effective not only for aryl chlorides, but also for aryl tosylates 21 to give 22 [22],... 

In addition, Peruzzini et al. developed, in 2007, iridium complexes of planar-chiral ferrocenyl phosphine-thioether ligands that were tested in the hydrogenation of simple alkyl aryl ketones.These complexes were diastereoselec-tively generated in high yields (85-90%) by addition of the corresponding... 

Scheme 8.33 Hydrogenations of alkyl aryl ketones with ferrocenyl phosphine-thioether ligands.

Another interesting family of phosphine ligands that has been applied to this coupling reaction is the ferrocenyl-phosphines. Some air-stable examples are showed in Figure 3. Compound 20 has been used for the coupling of aryl chlorides in combination with a Pd(0) source,while 21 gave excellent results for the coupling of a variety of aryl... 

Apart from these complexes, a number of heterodinuclear neutral compounds containing ferrocenyl derivatives as aryl ligands have also been prepared in recent years (see Table X). Most of them contain the ligand 2-(dimethylaminomethyl)ferrocenyl (FcN)104 106 and, with the sole exception of [(FcN)Au P(4-C1C6H4)3 ],106 have been... 

Heterodinuclear Neutral Complexes with Ferrocenyl Derivatives as Aryl Ligands... 

Ferrocenyl diphosphine core-functionalized carbosilane dendrimers have been prepared as ligands for homogeneous catalytic reactions applied in a CFMR by Van Leeuwen et al. [20,21,67,68]. The syntheses of these dppf-like ligands (Go-G2)-17 were performed using carbosilane dendritic wedges with an aryl bromide as focal point. These wedges were coupled to the core via quenching of the lithiated species with ferrocenyl phosphonites (Scheme 11). 

An addition to the literature on the arylation of protected hydrazines was recently contributed by Skerlj et al. [186]. In addition to the reactions of halopyridines with tert-butyl carbazate (H2NNHBoc) discussed in Section 4.3.2.3, these authors have reported the reaction of electron-deficient aryl bromides with this substrate. Reactions occurred when using DPPF or the ferrocenyl 11 as the ligand along with CS2CO3 as the base at temperatures of 100-110 °C. 

One key goal of catalyst development is to move from the more expensive alkyl and aryl iodides and bromides to the cheaper chlorides and the environmentally more desirable tosylates. The latter tend to react less well bnt the nse of basic, bulky ligands like P(tBn)3 and a nnmber of ferrocenyl-substituted phosphines has improved the situation. 

Very recently in a joint effort from industry and academia an improved Pd catalyst system based on bidentate ferrocenyl phosphine ligands was developed that enables the carbonylation of electron-deficient, electronically neutral, and electron-rich aryl chlorides in good to excellent yield [58]. The new catalyst represents a substantial improvement in efficiency, utility and practicability for... 

---