Fluorous chiral diamine

The hydrogen-transfer reduction of acetophenone under FBS conditions was also readily achieved in the presence of fluorous chiral diamines, diimines and (3-amino alcohols derived from tartaric acid (e.g. 18-20 Scheme 5.5) in combination with [Ir(COD)Cl]2 or Rii(p-cyrricri(jCJJ, [42], but much lower enantioselectivities (up to 31% ee in the case of 18/[Ir(COD)Cl]2) were obtained. 

Asymmetric transfer hydrogenation of ketones in the presence of soluble transition metal catalysts has been developed [8-10], enantioselectivities up to 99% ee being obtained using a ruthenium catalyst bearing mono-N-tosylated diphenyl-ethylenediamine as a ligand. Iridium complexes associated with fluorous chiral diimines 3a-3c or diamines 4a—4b have also been shown to be effective catalysts in hydrogen-transfer reduction of ketones [11,12]. 

A fluorous chiral organocatalyst (18) promotes the formation of the anti-Mol product (with up to 96% ee) on reaction between aromatic aldehydes with ketones in brine. The enantioselectivity achieved on promotion of aldol and Mannich reactions by another di-diamine-based catalyst (19) can be reversed by the addition of an achiral acid and is to be the subject of further mechanistic investigation. ... 

A fluorous thiourea organocatalyst 28 was conveniently prepared from a chiral diamine (Scheme 7.29) [45]. The fluorous thiourea 28 catalyzed the Michael reaction of maleimides and aldehydes with high yield and enantioselectivity. The catalyst 28 could be recycled by simple filtration and reused without significant loss of catalytic activity and enantioselectivity, while the catalyst recovery yield dropped dramatically after three cycles. 

An asymmetric hydrogen transfer of ketones was reported using chiral perfluorinated ligands in a 2-propanol/n-perfluooctane biphasic system. Several perfluorinated salen and diamine ligands were examined for the reaction catalyzed by the [Ir(COD)Cl]2 complex diamine 16 was found to be most effective (Scheme 20). The reaction was carried out at 70" C for 30 min and then the mixture was cooled to 0°C. The perfluorooctane solution was separated and used for the next reaction. The reactivity was almost the same as that of the first mn, and the enantioselectivity was higher (79% ee). Two further recyclings of the fluorous layer yielded the product with enantioselectivities up to 59% ee, but a decrease in activity was observed. 

Diamine-derived chiral copper complex 254 was used in the asymmetric cyclopropanation (Scheme 1.120) [177]. Perlluorinated diamine ligand 255 was developed and showed moderate levels of enantioselectivity for the cyclopropanation of diazoacetate (Scheme 1.121) [178]. The fluorous ligand was readily separated by the simple decantation of the fluorous phase. Although the recycling of the catalyst was expected, reuse was difficult because of its partial decomposition. 

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