Table 1.
Optimization of the isatin insertion reaction.
| |||
|---|---|---|---|
| Entry | Additive (mol %) | t (h) | Yielda (%) |
| 1 | DIPEA (20)/LiBr (20) | 48 | 0 |
| 2 | 2,6-lutidine (40) | 48 | 0 |
| 3 | DMAP (50) | 48 | 25 |
| 4 | DIPEA (100) | 48 | 63 |
| 5 | Et3N (200) | 18 | 99 |
| 6 | Et3N (50) | 24 | 99 |
| 7 | Et3N (20) | 48 | 21 |
| 8 | DBU (20) | 24 | 99 |
| 9 | DBU (10) | 24 | 82 |
| 10b | DBU (20) | 24 | 99 |
Reaction conditions: A solution of 1 (0.18 mmol) and 2 (0.15 mmol) in the presence of the additive in 0.4 mL of CH2Cl2 was stirred at 30 °C.
a
Determined by 1H NMR analysis.
b
CHCl3 was used as solvent. DIPEA = N,N-diisopropylethylamine, DMAP = 4-dimethylaminopyridine, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene.