Recyclable supported catalysts in microwave-assisted reactions:: first Diels-Alder cycloaddition of a triazole ring

We describe here the first example in which a 1,2,3-triazole ring acts as a diene towards DMAD in microwave-assisted solvent-free Diels-Alder cycloadditions. The extrusion of a molecule of a nitrile affords pyrazole derivatives as the products. The yields can be markedly increased by using a recyclable supported Lewis acid catalyst, which can be reused at least five times without a decrease in the yield. (c) 2006 Elsevier Ltd. All rights reserved.