Yasumasa Hamada and colleagues at Chiba University used a combination of nickel acetate and a commercially available phosphine ligand to catalyse the asymmetric hydrogenation of an alpha-amino-beta-keto ester hydrochloride. Although others have reported similar reactions, Hamada says this is the first time that a homogeneous chiral nickel catalyst has been used.
Precious metals, such as rhodium, iridium and ruthenium, play a crucial role as the central metal of homogeneous catalysts for asymmetric hydrogenation reactions. However, these metals are expensive and are becoming increasingly rare as we use up the natural resources. Hamada says he was motivated to find sustainable methods using abundant and cheap transition metals, such as nickel. 'Although the activity of the nickel catalyst is moderate at present, it is expected that the processes catalysed by precious transition metal complexes will be replaced by base transition metals in the near future,' he says.
Hamada plans to focus on finding more active nickel complexes, although he admits it won't be easy. 'Research using transition metal complexes is confronted with difficulty because there is no proper ligand giving high reactivity and selectivity,' he explains. 'The development of new ligands and counter-ions will provide the solution to this long standing problem.'
Original publication: Yasumasa Hamada et al., Chem. Commun., 2008.