Water Promoted One-pot Three-Step Synthesis of Novel N-Saccharin Isoxazolines/Isoxazoles Using KI/Oxone Under Ultrasonic Activation

A green and efficient regioselective protocol was developed for the preparation of novel isoxazolines and isoxazoles of N-saccharin derivatives via the water-promoted cycloaddition reaction of nitrile oxides with alkenes and alkynes. It is noteworthy that KI/Oxone/water-promoted one-pot three-component reactions of aldehyde, hydroxylamine hydrochloride, and alkene or alkyne were observed to be very satisfactory. The synthesis of all adducts (4a-j/5a-j) has been carried out by this method with high to excellent yields (70-95%) at 25°C within 30 min, using ultrasonic probe. All the new compounds were thoroughly characterized by spectroscopic techniques and also 5b, 5c and 5f were structurally identified by single-crystal X-ray diffraction methods. X-ray crystallography structure analysis clearly supported the regioselectivity of the cycloaddition reaction.