Enantiomeric Excess of 18F-FDOPA with Different Phase-Transfer Catalysts (1-3, Fig. 1)
| Entry | Catalyst | Base | Temperature (°C) | Enantiomeric excess (%) |
| 1 | 1 | CsOH⋅H2O | 0° | 96 |
| 2 | 1 | CsOH⋅H2O | RT | 38 |
| 3 (21) | 2a | CsOH⋅H2O | 0° | 96 |
| 4 | 2a | CsOH⋅H2O | RT | 92 |
| 5 | 2a | KOH 9N | RT | 93 |
| 6 | 2b | KOH 9N | RT | 87 |
| 7 | 2c | KOH 9N | RT | 84 |
| 8 | 2d | KOH 9N | RT | 52 |
| 9 | 2e | KOH 9N | RT | 97 |
| 10 | 3 | KOH 9N | RT | 97 |
RT = room temperature.
CsOH⋅H2O (150 mg) or KOH 9N (200 μL), Schiff base 8 (25 mg), 1–3 (2–3 mg), toluene (3 mL).