Initial screening of basesa.
| ||||
|---|---|---|---|---|
| Entry | Base | 3aa (%) | 4aa (%) | 3aa : 4aa |
| 1 | None | 10 | 11 | 48 : 52 |
| 2 | Pyridine | 2 | 28 | 7 : 93 |
| 3 | DIPEA | 80 | 9 | 90 : 10 |
| 4 | DABCO | 4 | 2 | 67 : 33 |
| 5 | DBU | 57 | 24 | 70 : 30 |
| 6 | Na2CO3 | 46 | 18 | 72 : 28 |
| 7 | K2CO3 | 59 | 31 | 66 : 34 |
| 8 | Cs2CO3 | 56 | 27 | 67 : 33 |
| 9 | NaHCO3 | 70 | 20 | 78 : 22 |
| 10 | KF | 42 | 35 | 55 : 45 |
| 11 | K3PO4 | 65 | 35 | 65 : 35 |
| 12 | KOt-Bu | 43 | 21 | 67 : 33 |
Reaction conditions: 1a (0.5 mmol), Ph2IOTf (1.2 equiv.), base (2 equiv.), toluene (2 mL), 100 °C, 16 h.