Highly efficient C-C bond-forming reactions in aqueous media catalyzed by monomeric vanadate species in an apatite framework

A calcium vanadate apatite (VAp), in which PO43- of hydroxyapatite (HAP), Ca-10(PO4)(6)(OH)(2), is completely substituted by VO43-in the apatite framework, was synthesized. Physicochemical analysis of the VAp reveals the presence of isolated VO4 tetrahedron units with a pentavalent oxidation state. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reactions using deuterium oxide. For example, a 200-mmol-scale Michael reaction under triphasic conditions proceeded rapidly, with an extremely high turnover number of up to 260 400 and an excellent turnover frequency of 48 s(-1). No vanadium leaching was detected during the above reactions, and the catalyst was readily recycled with no loss of activity.