Table 4. Optimization of the Catalyst, Synthesis Condition, and Solvent for the Synthesis of 4H-Pyran on the Model Reaction.
| entry | cat. & cat. amount (mg) | solvent | temp. (°C) | time (min) | yield (%) |
|---|---|---|---|---|---|
| 1 | rt | 120 | trace | ||
| 2 | 80 | 120 | trace | ||
| 3 | ethanol | rt | 120 | 10 | |
| 4 | ethanol | reflux | 120 | 17 | |
| 5 | Fe3O4@GA@IG (10) | ethanol | rt | 120 | 25 |
| 6 | Fe3O4@GA@IG (10) | ethanol | 50 | 100 | 38 |
| 7 | Fe3O4@GA@IG (10) | ethanol | reflux | 40 | 84 |
| 8 | Fe3O4@GA@IG (10) | acetonitrile | reflux | 60 | 52 |
| 9 | Fe3O4@GA@IG (10) | chloroform | reflux | 75 | 50 |
| 10 | Fe3O4@IG (20) | ethanol | ultrasound | 60 | 51 |
| 11 | Fe3O4@IG (20) | ethanol | reflux | 15 | 92 |
| 12 | Fe3O4@IG (25) | ethanol | reflux | 15 | 92 |
| 13 | Fe3O4@GA@IG (5) | ethanol | reflux | 60 | 83 |
| 14 | Fe3O4 NPs (20) | ethanol | reflux | 60 | 54 |
| 15 | IG (20) | ethanol | reflux | 50 | 67 |