Potassium dodecatungstocobaltate trihydrate (K5CoW12O40•3H2O):: A mild and efficient reusable catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation

A simple and efficient procedure has been developed for the preparation of aryl-14H-dibenzo[a.j]xanthenes by a one-pot condensation of beta-naphthol and aryl aldehydes, in the presence of potassium dodecatungstocobaltate trihydrate [K5CoW12O40 center dot 3H(2)O, (0.01 mol%)] as a heterogeneous catalyst in a solvent-free media using both conventional heating and microwave irradiation. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times (1.5-2.0 h and 2.0-3.0 min) and milder conditions and the catalyst exhibited remarkable reusable activity. (c) 2006 Elsevier B.V. All rights reserved.