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

Abstract 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 (S O, C N, C O and C C). 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.