A solvent-free synthesis of coumarins using a Wells-Dawson heteropolyacid as catalyst

作者：Romanelli GP; Bennardi D; Ruiz DM; Baronetti G; Thomas HJ; Autino JC^*

来源：Tetrahedron Letters, 2004, 45(48): 8935-8939.

DOI：10.1016/j.tetlet.2004.09.183

• coumarin
• heteropolyacid
• Wells-Dawson catalyst
• Pechmann reaction
• 4-methylumbelliferone

Substituted coumarins are synthesized from phenols and beta-ketoesters by the Pechmann reaction, using a Wells-Dawson heteropolyacid (H(6)P(2)W(18)O(62)(.)24H(2)O) as catalyst by a solvent-free procedure. This one requires low reaction times, 130degreesC temperature and as little as 1 mol% of Wells-Dawson acid, obtaining good to excellent yields of coumarins. The catalyst showed to be reusable with no differences in the yields. The results are compared with those of the reactions performed in toluene solution. The presented synthetic procedure is a convenient, clean and fast alternative for synthesizing 4-substituted coumarins (17 examples).

• 出版日期2004-11-22