Mild Friedel-Crafts Acylation of Furan with Carboxylic Acids and the Heterogeneous Catalyst Couple AlPW12O40 / Mg(OH)2

Many bioactive compounds contain 2-furanoyl moieties. Classical Friedel-Crafts acylation conditions fail completely in the case of the sensitive and polymerization-prone furan, or give only rather unsatisfying yields only. The heterogeneous catalyst couple consisting of equimolar amounts of the stable and non-hygroscopic heteropolyacid aluminum dodecatungstophosphate (AlPW12O40)1 in combination with Mg(OH)2 was used for the direct reaction between furan and a variety of free carboxylic acids to regioselectively produce 2-furyl-alkylketones and 2-furyl-arylketones in good to excellent yields. The approach worked even in cases of labile benzofuran and indole derivatives where all alternative approaches failed.