Synthesis of one-pot pyrazolo[4′,3′:5,6]pyrano[2,3-<i>c</i>]phenazin-15-yl) methanone derivatives <i>via</i> a multi-component using Fe₃O₄@TiO₂-SO₃H as a recoverable magnetic catalyst under microwave irradiation

A new one-pot method for the synthesis four-component of pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl)methanone derivatives has been developed in the presence of nano Fe₃O₄@TiO₂-SO₃H catalysts (heterogeneous acid) under microwave conditions and in a solvent-free environment at 180 W. One of the benefits of using this catalyst was its re-use in subsequent stages of its reaction without much loss in its activity, which was carried out by an external magnet and recovered. The catalyst was synthesized and characterized by XRD, EDX, TEM, FESEM, TGA-DTA, BET, VSM and AFM. The productivity of the products obtained from this protocol (MAOS) is significantly high and the shorter reaction time in the synthesis process over the reflux method. These results showed advantages for synthesis, such as mild reaction conditions, no use of toxic catalysts in the laboratory, solvent-free environment, low energy consumption and Economically Affordable.本研究开发了一种以纳米Fe₃O₄@TiO₂-SO₃H（非均相酸）为催化剂，在180 W微波辐射、无溶剂环境下合成吡唑并[4′,3′:5,6]吡喃并[2,3-c]吩嗪-15-基甲酮衍生物的四组分一锅法新方法。该催化剂可通过外磁场回收并重复使用，且重复使用过程中活性无明显衰减。研究者通过X射线衍射（XRD）、能量色散X射线光谱（EDX）、透射电子显微镜（TEM）、场发射扫描电子显微镜（FESEM）、热重-差热分析（TGA-DTA）、比表面积测试（BET）、振动样品磁强计（VSM）及原子力显微镜（AFM）对所制备的催化剂进行了合成与表征。本方案（MAOS）所得产物的产率显著高于传统回流法，且反应时长更短。该合成方案具备诸多优势：反应条件温和、无需使用实验室有毒催化剂、采用无溶剂体系、能耗较低且经济实惠。