Table 2. Organocatalyzed Oxindole Synthesisa.
| entry | variation from the standard conditions | conv.b |
|---|---|---|
| 1 | none | 62% |
| 2 | 1b·H+ | 49% |
| 3 | 1c·H+ | 4% |
| 4 | 2a (5 mol %); 0.7 equiv of Cs2CO3 | 80% |
| 5 | 2b (5 mol %); 0.7 equiv of Cs2CO3 | 38% |
| 6 | 2c (5 mol %); 0.7 equiv of Cs2CO3 | 16% |
| 7 | [2a•+]PF6 (5 mol %); 0.7 equiv of Cs2CO3 | 90% |
| 8 | [2b•+]PF6 (5 mol %); 0.7 equiv of Cs2CO3 | 60% |
Standard reaction conditions: 3 (0.3 mmol), precatalyst [1a·H+]PF6 (0.03 mmol), Cs2CO3 (0.24 mmol), 1,4-dioxane (1.0 mL), Ar atmosphere, 100 °C (oil bath), 16 h.
Estimated from 1H NMR with 1,3,5-trimethoxybenzene (TMB) as internal standard.
