Green one-pot four-component synthesis of 3,5-disubstituted isoxazoles- sulfonates and sulfonamides using a combination of NaDCC as metal-free catalyst and ultrasonic activation in water
Résumé
A simple and green one-pot reaction has been proposed for the synthesis of novel 3,5-disubstituted isoxazole-sulfonates and -sulfonamides (5a-j) in water under ultrasound irradiation. The methodology is based on the use of safe and environmentally friendly reagents and allows, via in-situ 1,3-dipolar cycloaddition, an easy access to functionalized heterocycles with the creation of four new bonds (Ssingle bondO, Csingle bondN, Csingle bondO and Csingle bondC). Comparison studies using classical magnetic stirring and ultrasound irradiation clearly showed that sonication promoted clean transformation, high yields (72–89%) and faster reactions (20–28 min). All the synthesized compounds were fully characterized by MS-ES, 1H NMR, 13C NMR spectroscopy and HPLC analysis.