Table 2. Effect of Cocatalysts and Oxidants on HMF Conversion and DFF Yield in AcOHa.
| entry | cocatalyst, loading (mol %) | oxidant (mmol) | time (h) | conv. HMF (%) | yield DFF (%) | select.b (%) |
|---|---|---|---|---|---|---|
| 1 | TEMPO, 0 | O2 | 5 | 17 | 0 | 0 |
| 2 | TEMPO, 2 | O2 | 5 | 85 | 69 | 81 |
| 3 | TEMPO, 5 | O2 | 5 | 100 | 95 | 95 |
| 4 | TEMPO, 5 | air | 5 | 82 | 81 | 99 |
| 5 | NHPI, 5 | O2 | 24 | 37 | 3 | 8 |
| 6 | DDQ (2) | 24 | 18 | 4 | 22 | |
| 7 | TBHP (2) | 24 | 46 | 1 | 2 | |
| 8 | H2O2 (2) | 24 | 30 | 0 | 0 |
a
Reaction conditions: HMF (1 mmol, 126 mg), Fe(NO3)3·9H2O (0.05 mmol), 50 °C, AcOH (2 mL), and oxygen balloon; the conversion and yield were determined by HPLC. Conv. = conversion. Select. = selectivity.
b
S (DFF) = yield (DFF)/conversion (HMF).