A comprehensive review on magnetic manganese as catalysts in organic synthesis

Abstract

Manganese-based magnetic catalysts have gained significant attention in modern catalysis due to their unique combination of high catalytic efficiency, magnetic recoverability, and environmental sustainability. These catalysts, typically composed of manganese oxides, manganese-doped ferrites, or Mn-functionalized magnetic nanoparticles, facilitate a wide range of chemical transformations, including oxidation reactions, coupling reactions, and multicomponent reactions especially in the synthesis of heterocycles. Their ability to exhibit multiple oxidation states, strong redox activity, and high surface area makes them highly effective in selective and energy-efficient catalytic processes. Additionally, their magnetic properties enable easy separation from reaction mixtures using an external magnetic field, improving catalyst recyclability and reducing operational costs. Compared to conventional catalysts, magnetic manganese catalysts offer superior stability, cost-effectiveness, and eco-friendliness, making them promising alternatives for industrial-scale applications. This review explores recent advancements in the synthesis, mechanistic insights, and diverse applications of magnetic manganese catalysts, highlighting their role in sustainable and green chemistry. Furthermore, the challenges and future perspectives in optimizing their performance for broader catalytic applications are discussed. The insights presented in this review underscore the growing importance of magnetic manganese catalysts in developing efficient, cost-effective, and environmentally benign catalytic systems.

Fig. 1. Catalysis by homogenous and heterogenous catalysts.

Fig. 2. Advantages of magnetic nanocatalysts.

Fig. 3. Superiority of manganese over other transition metals in catalysis.

Scheme 1. General method to construct the Fe₃O₄@SiO₂–NH₂@[Mn(TPFPP)OAc] nanocomposite.

Scheme 2. Epoxidation of alkenes [catalysis by Fe₃O₄@SiO₂–NH₂@[Mn(TPFPP)OAc] nanocomposite].

Scheme 3. General method to construct the MNP@SiO₂[4-NH-Mn-TDCPP] nanocomposite.

Scheme 4. Epoxidation of alkynes [catalysis by MNP@SiO₂[4-NH-Mn-TDCPP] nanocomposite].

Scheme 5. General method to construct the Fe₃O₄@MCM-41-Im@MnPor nanocomposite.

Scheme 6. Epoxidation of alkynes [catalysis by Fe₃O₄@MCM-41-Im@MnPor nanocomposite].

Scheme 7. General method to construct the Fe₃O₄@SiO₂–[MnL(OAc)] nanocomposite.

Scheme 8. Epoxidation of alkynes [catalysis by Fe₃O₄@SiO₂–[MnL(OAc)] nanocomposite].

Scheme 9. Oxidation of sulfides to sulfoxides by H₂O₂ [catalysis by Fe₃O₄@SiO₂–[MnL(OAc)] nanocomposite].

Scheme 10. General method to construct the Fe₃O₄@SiO₂–[MnL(OAc)] nanocomposite.

Scheme 11. Oxidation of sulfides to sulfoxides by UHP [catalysis by Fe₃O₄@SiO₂–[MnL(OAc)] nanocomposite].

Scheme 12. Oxidation of sulfides to sulfoxides by H₂O₂ [catalysis by Mn₂ZnO₄] nanocomposite].

Scheme 13. Oxidation thiols to disulfides [catalysis by Fe₃O₄@SiO₂–NH₂@Mn(iii) nanocomposite].

Scheme 14. Oxidation selective of benzyl alcohols into benzaldehydes [catalysis by MnFe₂O₄ nanocomposite].

Scheme 15. Suggested mechanism for oxidation selective oxidation of benzyl alcohols into benzaldehydes [catalysis by MnFe₂O₄ nanocomposite].

Scheme 16. Synthesis of triaryl imidazoles [catalysis by MnFe₂O₄ nanocomposite].

Scheme 17. General method for construction of Fe₃O₄@SiO₂–ABMA–MnCl₂ nanocomposite.

Scheme 18. Synthesis of triaryl imidazoles [catalysis by Fe₃O₄@SiO₂–ABMA–MnCl₂ nanocomposite].

Scheme 19. Suggested mechanism for synthesis of triaryl imidazoles [catalysis by Fe₃O₄@SiO₂–ABMA–MnCl₂ nanocomposite].

Scheme 20. Synthesis of benzimidazoles [catalysis by MnFe₂O₄ nanocomposite].

Scheme 21. Synthesis of quinoxalines [catalysis by MnFe₂O₄ nanocomposite].

Scheme 22. Suggested mechanism for synthesis of benzimidazoles [catalysis by MnFe₂O₄ nanocomposite].

Scheme 23. General method for construction of [Fe₃O₄@PAM–Schiff-base–Mn][ClO₄] nanocomposite.

Scheme 24. Synthesis of 1,2,3-substituted triazoles [catalysis by [Fe₃O₄@PAM–Schiff-base–Mn][ClO₄] nanocomposite].

Scheme 25. Suggested mechanism for synthesis of 1,2,3-substituted triazoles [catalysis by [Fe₃O₄@PAM–Schiff-base–Mn][ClO₄] nanocomposite].

Scheme 26. General method for construction of Fe₃O₄@SiO₂@Mn-complex.

Scheme 27. Synthesis of 7-aryl[4,3-d]pyrido[1,2-a]pyrimidin-6(7H)-ones [catalysis by Fe₃O₄@SiO₂@Mn nanocomposite].

Scheme 28. Suggested mechanism for synthesis of 7-aryl[4,3-d]pyrido[1,2-a]pyrimidin-6(7H)-ones [catalysis by Fe₃O₄@SiO₂@Mn nanocomposite].

Scheme 29. Synthesis of 1,4-dihydropyridines [catalysis by MnFe₂O₄ nanocomposite].

Scheme 30. General method for construction of Fe₃O₄@CSBMn nanocomposite.

Scheme 31. Synthesis of imidazo[1,2-a]pyridines [catalysis by Fe₃O₄@CSBMn nanocomposite].

Scheme 32. Suggested mechanism for synthesis of imidazo[1,2-a]pyridines [catalysis by Fe₃O₄@CSBMn nanocomposite].

Scheme 33. General method to construct Mn₂O₃-doped Fe₃O₄ NPs nanocomposite [MRC-1].

Scheme 34. Synthesis of alpha-aminonitriles from alcohols and amines [catalysis by Mn₂O₃-doped Fe₃O₄ NPs nanocomposite].

Scheme 35. Synthetic pathway for synthesis of alpha-aminonitriles from alcohols and amines [catalysis by Mn₂O₃-doped Fe₃O₄ NPs nanocomposite].

Scheme 36. Synthesis of 3-benzylated indoles [catalysis by MnFe₂O₄ nanocomposite].

Scheme 37. Suggested mechanism for synthesis of 3-benzylated indoles [catalysis by MnFe₂O₄ nanocomposite].

Scheme 38. Synthesis of spirooxindole derivatives [catalysis by MnFe₂O₄ nanocomposite].

Scheme 39. Suggested mechanism for synthesis of spirooxindole derivatives [catalysis by MnFe₂O₄ nanocomposite].