The development of ruthenium containing amphiphilic nano-reactor systems for transfer hydrogenation reactions in aqueous media

Catalytic transfer hydrogenation and asymmetric transfer hydrogenation reactions an efficient method to obtain chiral and achiral alcohol derivatives obtained from ketone and aldehyde derivatives. Following the advancements in organometallic chemistry, iridium, rhodium and ruthenium based efficient organometallic catalyst were reported, however only a few catalyst was found to be compatible with water media. The hydrophobic nature of ketone/aldehyde substrates and the catalyst that are used in transfer hydrogenation reactions prevents the conversion of these reactants in water media. In the context of this study, a new generation amphiphilic polymer based ruthenium nanoreactor system was designed using a novel approach to overcome the above mentioned limitations. Amphiphilic polymers were obtained through ring opening metathesis polymerization reactions of norbornene derivatives bearing hydrophobic and hydrophilic groups in the presence of chiral ligant precursors acting as the chain transfer agents. The macromolecular ruthenium nano reactor systems were prepared through coordination of [RuCl2(p-simen)]2 on diamine based chiral group substituted amphiphilic polymers. The obtained nano reactor systems formed spherical micelle structures with varying sizes between 140-160 nm in aqueous medium. This micelle catalyst system catalyzed the transfer hydrogenation of acetophenone with 1% mol Ru loading with 99 % conversion and 95 % enantioselectivity. The catalyst can be easily recycled from the reaction mixture in micelle form in water media and can be used up to ninth run in asymmetric transfer hydrogenation reactions.