Ligands ferrocenyl diamines

With ferrocenyl diamines such as 32, the transfer hydrogenation of I -acetonaphthone reached 90 % ee at -30 °C with 2-propanol as the hydrogen source [63]. Even amino acids have been used as ligands for ruthenium [64, but, more than 90 % ee results only when tetralone is the substrate. 

In 1997 the first asymmetric aza-Claisen rearrangement was reported by Overman et al. [55], which made use of diamines as bidentate ligands for Pd(II), allowing for moderate enantioselectivities. In the same year, Hollis and Overman described the application of the planar chiral ferrocenyl palladacycle 38 as a catalyst for the enantioselective aza-Claisen rearrangement of benzimidates 39 (Fig. 19) [56]. A related ferrocenyl imine palladacycle provided slightly inferior results, while a benzylamine palladacycle lacking the element of planar chirality was not able to provide any enantioselectivity [57]. 

Interestingly, the chhal diamine 508 catalyzes the enantioselective addition of boronic acids to aromatic ketone.s like acetophenone. The reaction produces interesting tertiary diarylcarbinols such as 509 in up to 93% ee. Bolm and coworkers have shown that this approach can also be used for a simple preparation of chiral diarylcarbinols (such as 510) in the presence of the chiral ferrocenyl ligand 511 (Scheme 122) . The addition of... 

Investigation of the production of planar chiral ferrocene derivatives of use in catalytic asymmetric chemistry has led to the lithiation of N,AI-dimethylferrocenylmethylamine in the presence of non-stoichiometric levels of the chiral diamine tmcda (20% wrt ferrocenyl ligand). Data suggest the ability of this ligand to promote catalytic stereoselective ortho lithiation through the facile ability of Et20 to replace the chiral auxiliary as the lithiate converts from tmcda-complexed monomer to Et20-complexed dimer with retention of stereochemistry. ... 

The reaction of the isomeric 4,6-dichloropyrimidine 34 with the same diamines gave similar results (Scheme 16). Longer diamines 2b,k afforded macrocycles 35b,k in rather good yields (31%) while a shorter 2j provided 35j in 10% yield. We tried other ligands than BINAP to improve the yields, but only iV,/V-dimethyl-l-[2-(diphenylphosphino)ferrocenyl]ethylamine was of the same elBciency as BINAP 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (Xanthphos) and DavePHOS provided only acyclic monoamination products. 

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