Noyori–Ikariya catalyst supported on tetra-arylphosphonium salt for asymmetric transfer hydrogenation in water

A straightforward synthesis of a tetraarylphosphonium (TAP)-supported Noyori–Ikariya catalyst is described. The TAP-supported ruthenium precatalyst provided good conversions and high enantioselectivities for the asymmetric transfer hydrogenation of ketones in water. In addition the catalyst was easily recovered and used in multiple catalytic cycles.