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Highly Efficient C−C Bond-Forming Reactions in Aqueous Media Catalyzed by Monomeric Vanadate Species in an Apatite Framework

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journal contribution
posted on 15.09.2006, 00:00 by Takayoshi Hara, Satoko Kanai, Kohsuke Mori, Tomoo Mizugaki, Kohki Ebitani, Koichiro Jitsukawa, Kiyotomi Kaneda
A calcium vanadate apatite (VAp), in which PO43- of hydroxyapatite (HAP), Ca10(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.