Hydroxyapatite as a new solid support for the Knoevenagel reaction in heterogeneous media without solvent

Knoevenagel condensation is easily carried out without a solvent at room temperature using hydroxyapatite (HAP). Activation by water and benzyltriethylammonium chloride (BTEAC) has also been investigated. When used with water and ammonium salt, hydroxyapatite is an excellent solid support for the Knoevenagel condensation, leading to excellent yields in a few minutes. Taking into account environmental and economical considerations, the handling of hydroxyapatite used here presents many advantages such as easier separation and recovery from the reaction mixture and thus, enhanced recycling possibilities, which are now well established in fine organic synthesis. (C) 2002 Elsevier Science B.V. All rights reserved.