Physicochemical characterization of benzalkonium chloride and urea based deep eutectic solvent (DES): A novel catalyst for the efficient synthesis of isoxazolines under ultrasonic irradiation

Various novel deep eutectic solvents (DESs) have been prepared by combining different molar ratio of benzalkonium chloride and urea, subsequently characterized for some physical and spectroscopic properties. Among newly formed DESs, one of the mixture (1:2) was employed in combination with ultrasound (US), for the synthesis of selective isoxazoline derivatives. The reactions were also performed by nonultrasonic (NUS)/thermal method using conventional solvent system for comparison purposes. Applying DES, as a reaction medium in either of the thermal and ultrasonic assisted methods, an appreciable improvement in the product yield was achieved in a shorter time. The results show some advantages in terms of reaction time and energy consumption when DES and ultrasound combination was used for the synthesis of isoxazolines. Recyclability attributes of DES were also studied which revealed that a marginal decrease in the yield (%) was recorded up-to four runs. The findings of this study support the use of DES in combination with ultrasound technique as a viable green route for the synthesis of isoxazoline derivatives.