Highly efficient synthesis of coumarin derivatives in the presence of H14[NaP5W30O110] as a green and reusable catalyst

A variety of heteropolyanions including: Keggin, Dawson, Preyssler, mixed addenda and sandwich types, catalyzed the formation of 4-methylnaphtho-(1,2-b)-pyran-2-one (coumarin) from the condensation of a-naphthol and ethylacetoacetate in a solvent free system and under heating conditions. Our data vividly indicate that sodium30-tungsto pentaphosphate, [NaP5W30O110](14-), which so-called Preyssler's anion, with high hydrolytic (pH 0-12) and thermal stability is the catalyst of choice. This catalyst catalyzed the synthesis of other coumarin derivatives in high yields and good selectivity. (c) 2007 Elsevier B.V. All rights reserved.