Table 3. Use of Different Lewis Acid and Lewis Base by Microwave Irradiation (M.W) For Compound 4.
| entry | cat (mol %) | conditionsb | yield (%)a |
|---|---|---|---|
| 1 | no catalyst no M.W | water/ethanol, 1 day | trace |
| 2 | no catalyst | water/ethanol, 1 h | 45 |
| 3 | AlCl3 (15) | water/ethanol, 3 min | 49 |
| 4 | MgCl2 (15) | water/ethanol, 3 min | 47 |
| 5 | FeCl3·6H2O (15) | water/ethanol, 3 min | 56 |
| 6 | Fe(OTf)3 (15) | water/ethanol, 3 min | 69 |
| 7 | ZnBr2 (15) | water/ethanol, 3 min | 74 |
| 8 | CuCl2 (15) | water/ethanol, 3 min | 66 |
| 9 | PdCl2 (15) | water/ethanol, 3 min | 87 |
| 10 | Pd(OAC)2(15) | water/ethanol, 3 min | 89 |
| 11 | p-TsOH (15) | water/ethanol, 3 min | 75 |
| 12 | Et3N (15) | water/ethanol, 3 min | 67 |
| 13 | TBABrc (15) | water/ethanol, 3 min | 66 |
| 14 | TiCl4 (15) | water/ethanol, 3 min | 71 |
| 15 | l-Proline (15) | water/ethanol, 3 min | 84 |
| 16 | Cys (15) | water/ethanol, 3 min | 98 |
| 17 | Cys (15) | ||
| No M.W | water/ethanol, 3 min | 88 |
a
Isolated yields based on 4.
b
Reaction conditions: 1 (1 mmol), 2a (1.5 mmol), and 3a (1 mmol) in a mixture of water and ethanol (3:1 ratio) by microwave irradiation conditions, 3 min.