Ferrocenyl itaconates

Itaconic acids are reduced in very high enantiomeric excesses (>97%) with Rh-TangPhos catalysts 658 Itaconic acid is reduced in 99.5% ee with the sugar-derived ferrocenyl phosphine 123.659... 

Recently Togni et al. [19] focussed on the preparation of asymmetric dendrimer catalysts derived from ferrocenyl diphosphine ligands anchored to dendritic backbones constructed from benzene-1,3,5-tricarboxylic acid trichloride and adamantane-l,3,5,7-tetracarboxylic acid tetrachloride (e.g. 11, Scheme 11). In situ catalyst preparation by treatment of the dendritic ligands with [Rh(COD)2]BF4 afforded the cationic Rh-dendrimer, which was then used as a homogeneous catalyst in the hydrogenation reaction of, for example, dimethyl itaconate in MeOH. In all cases the measured enantioselectivity (98.0-98.7%) was nearly the same as observed for the ferrocenyl diphosphine (Josiphos) model compound (see Scheme 11). 

Togni et al.169 synthesized dendrimers using a cyclophosphazene core and 16 peripheral chiral ferrocenyl ligands (Figure 10.13). The periphery of these ferrocenyldiphosphine metallo-dendrimers was decorated with [Rh(COD)2][BF4] to instill the desired catalytic properties necessary to reduce dimethyl itaconate. These metalloconstructs showed 98% ee, which compared well with the 99% ee obtained with monomeric Rh-based josiphos catalyst. 

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