Acid-catalyzed intramolecular oxa-Michael addition reactions under solvent-free and microwave irradiation conditions

The acid-catalyzed intramolecular oxa-Michael addition of (E)-1-aryl-4-hydroxy-4-methyl- -pent-1-en-3-ones under solvent-free and microwave irradiation conditions has been investigated. The results showed that Bronsted acids are more efficient than Lewis acids in this reaction. Up to 90% conversion and 81% yield were obtained using trifluoromethanesulfonic acid (triflic acid) as the catalyst, with short reaction times and an environmentally benign procedure.