Table 1.
Sodium borohydride reduction of isatin (6.8 mmol) under solvent-free microwave irradiation.
| Entry | Conditions | Time (min) | Products (% yield) | Rf value |
|---|---|---|---|---|
| 1 | SiO2 (10.0 g), NaBH4 (1.2 equiv) | 5 | NR | - |
| 2 | SiO2 (5.0 g), NaBH4 (2.3 equiv) | 5 | NR | - |
| 3 | SiO2 (5.0 g), NaBH4 (2.3 equiv) | 10 | 1 (26 %), P2, ∗2 | 0.90, 0.82, ∗0.48 |
| 4 | SiO2 (5.0 g), NaBH4 (2.3 equiv) | 20 | 1 (30 %), P2, ∗2 | 0.88, 0.81, ∗0.45 |
| 5 | Al2O3 (acidic) (5.0 g), NaBH4 (2.3 equiv) | 20 | NR | - |
| 6 | Al2O3 (basic) (10.0 g), NaBH4 (2.3 equiv) | 5 | NR | - |
| 7 | Al2O3 (basic) (10.0 g), NaBH4 (2.3 equiv) | 10 | 1 (32 %), ∗2 | 0.87, ∗0.44 |
| 8 | MgSO4.7H2O (10.0 g), NaBH4 (2.3 equiv) | 10 | NR | - |
| 9 | MgSO4.7H2O (10.0 g), NaBH4 (2.3 equiv) | 30 | 1 (12 %), P2, P3, ∗2 | 0.88, 0.82, 0.75, ∗0.45 |
| 10 | +2-N-COCH3, Al2O3(basic) (10.0 g), NaBH4 (2.3 equiv) | 5 | NR | - |
| 11 | +2-N-COCH3, Al2O3(basic) (10.0 g), NaBH4 (2.3 equiv) | 20 | 1 (20 %), ∗2 | 0.88, ∗0.46 |
NR = No Reaction; ∗2 = unreacted isatin; P2, P3 = unidentified products; +2-N-COCH3 = 1-acetylisatin