Entry | Catalyst | Conditions | Time | Yield (%) | Ref |
---|---|---|---|---|---|
1 | SnCl2/nano SiO2 | EtOH/reflux | 40 min | 94 | [31] |
2 | Silica-bonded N-propyl sulfamic acid (SBNPSA) | EtOH/reflux | 3–4 h | 90–95 | [32] |
3 | nanoZnO (5 mol %) | Solvent free/60 °C | 10 h | 95 | [33] |
4 | NH4H2PO4 (5 mol %) or NH4H2PO4/SiO2 | Solvent free/100 °C | 2 h | 85 | [34] |
5 | Fe3O4@mesoporous SBA-15 | EtOH/65 °C | 6 h | 85 | [35] |
6 | Fe3O4@PVA-SO3H (50 mg) | EtOH/reflux | 10 min | 99 | This work |