Optimization of the reaction conditionsa.
| ||||
|---|---|---|---|---|
| Entry | Photocatalyst | Additive | Solvent | Yieldb (%) |
| 1 | Rose bengal | — | CH3CN | 36 |
| 2 | Eosin Y | — | CH3CN | 18 |
| 3 | Rhodamine 6G | — | CH3CN | n. d. |
| 4 | Fluorescein | — | CH3CN | n. d. |
| 5 | Ir(ppy)3 | — | CH3CN | 23 |
| 6 | Rose bengal | Cs2CO3 | CH3CN | 51 |
| 7 | Rose bengal | K2CO3 | CH3CN | 38 |
| 8 | Rose bengal | DBU | CH3CN | 21 |
| 9 | Rose bengal | DABCO | CH3CN | 14 |
| 10 | Rose bengal | NaOAc | CH 3 CN | 72 |
| 11 | Rose bengal | NaOAc | THF | 68 |
| 12 | Rose bengal | NaOAc | DCE | 60 |
| 13 | Rose bengal | NaOAc | Toluene | 45 |
| 14 | Rose bengal | NaOAc | DMSO | 51 |
| 15 | — | NaOAc | CH3CN | n. d. |
| 16c | Rose bengal | NaOAc | CH3CN | n. d. |
| 17d | Rose bengal | NaOAc | CH3CN | 70 |
| 18e | Rose bengal | NaOAc | CH3CN | n. d. |
| 19f | Rose bengal | NaOAc | CH3CN | n. d. |
| 20g | Rose bengal | NaOAc | CH3CN | n. d. |
a
Standard conditions: 1a (0.2 mmol), 2a (0.4 mmol), photocatalyst (5 mol%), additive (0.4 mmol), solvent (2 mL), and irradiation with a 20 W blue LED for 12 h, air, n. d. = not detected.
b
Isolated yields.
c
Without light.
d
Under O2.
e
Under N2.
f
CuI (5 mol%).
g
Cu(OAc)2 (5 mol%).