Table 4. Evaluation of Various Catalysts for the Synthesis of N-Amino-2-pyridones in Comparison with MIL-101(Cr)-N(CH2PO3H2)2 in Ethanol under Reflux Conditions.
| entry | catalyst | amount of catalyst (mol %) | time (min) | yield (%) |
|---|---|---|---|---|
| 1 | MIL-101(Cr)-N(CH2PO3H2)2 | 5 mg | 20 | 92 |
| 2 | MIL-101(Cr)-NH2 | 5 mg | 60 | 24 |
| 3 | [Py-SO3H]Cl51 | 10 | 35 | 82 |
| 4 | Fe3O4@SiO2@PrNH252 | 5 mg | 60 | 25 |
| 5 | SSA53 | 10 | 25 | 85 |
| 6 | TrBr | 15 | 60 | 65 |
| 7 | p-TSA | 10 | 45 | 65 |
| 8 | nano-SB-[PSIM]Cl54 | 10 | 35 | 78 |
| 9 | TrCl | 10 | 45 | 72 |
| 10 | GTBSA55 | 10 | 30 | 85 |
| 11 | [Fe3O4@SiO2@Pr-DABCO-SO3H]Cl256 | 10 mg | 35 | 82 |
| 12 | FeCl3 | 10 | 50 | 75 |
| 13 | Al(HSO4)3 | 10 | 45 | 75 |
| 14 | H3[p(W3O10)4]·xH2O | 15 | 60 | 75 |
| 15 | Fe3O4 | 10 mg | 55 | 68 |
| 16 | trichloroisocyanuric acid | 10 | 55 | 70 |
| 17 | Et3N | 20 | 60 | trace |
| 18 | NaHSO4 | 10 | 60 | 35 |
| 19 | H3PO3 | 10 | 20 | 75 |
| 20 | H3PO3 + MIL-101(Cr)-NH2 | 5 + 5 | 20 | 90 and without recycling |