Magnetically separable new Fe3O4@AgZr2(PO4)3 nanocomposite catalyst for the synthesis of novel isoxazole/isoxazoline-linked 1,2,3-triazoles in water under ultrasound cavitation

In this work, we report a novel magnetically separable Fe3O4@AgZr2(PO4)3 as heterogeneous nano-composite catalyst for the one-pot four-step cascade sulfonylation/Huisgen 1,3-dipolar cycloaddition/azidation/click reactions in water under ultrasound cavitation. This strategy appears to be suitable for obtaining new analogues of isoxazole/isoxazoline-linked 1,4-disubstituted 1,2,3-triazoles in sustainable way starting from propargyl or allyl alcohol/sulfonyl chloride/oximes/sodium azide/and terminal alkynes. The effects of ultrasonic probe position as well as vessel shape on the chemical reaction were investigated. Three different types of 25 mL glass vessels were used in this study: round-bottomed flasks, erlenmeyer flasks and pear-shaped flasks. The heterogeneous nanocomposite was synthesized by supporting magnetic Fe3O4 nanoparticles on AgZr2(PO4)3 material (Fe3O4@AgZr2(PO4)3). The crystalline nature and purity of the catalyst were characterized using various techniques, including FT-IR, EDX, and XRD. Dispersity and morphology were characterized by SEM analysis. The findings indicate that Fe3O4 particles ranging in size from 50 to 75 nm were evenly distributed on the surface of AgZr2(PO4)3. The use of an aqueous reaction medium, the simple and inexpensive recovery of the catalyst by the application of an external magnet and the high and constant catalytic efficiency over at least five consecutive cycles make this protocol more interesting from an operational point of view. All synthesized products 6a-j and 7a-f were prepared in excellent yields (86-95 %) in short reaction time (2.25h). Their structures were confirmed by FT-IR, 1H NMR, 13C NMR, ESI-MS and HPLC analyses.