Water-based reactions hydrophilic ligands

Another pyrrolidone-based phosphine has been incorporated into amphiphilic, water-soluble diblock co-polymers based on 2-oxazalone derivatives (Scheme 61). The synthesis involved the initial preparation of a diblock co-polymer precursor with ester functionalities in the side chain. This was achieved by sequential polymerization of 2-methyl-2-oxazoline to form the hydrophilic block that provides water solubility, and subsequently a mixture of ester-functionalized oxazoline 147 and 2-nonyl-2-oxazoline, the latter increasing the hydrophobicity of the second polymer block. Having made the backbone, the ester functionalities were converted into carboxylic acids giving polymer 148, which was then reacted with the phosphine ligand to give the desired supported material, 149. This was used in asymmetric hydrogenation reactions with success. 

The participation of hydrophilic phosphine ligand is not necessary. The reaction can be catalyzed by water-insoluble complex PdCl2(PPh3)2 in the presence of a stoichiometric amount of inorganic base K2CO3 and a substoichiometric amount of BU3N, which apparently performs the role of phase-transfer agent (Scheme Alternatively, the reac-... 

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