Table 3. Radiosynthesis of [11C]1A.
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| Entry a | DBU (equiv.) | Mitsunobu reagents (equiv.) | T (°C) | RCY of [11C]1A b (%) |
| 1 c | 0.05 | 2 | 20 | 0 g |
| 2 c | 1 | 1 | 20 | 2 f |
| 3 d | 1 | 1 | 20 | 5 f |
| 4 d | 2.5 | 1 | 20 | 4 f |
| 5 d | 5 | 1 | 20 | 8 f |
| 6 d | 10 | 1 | 20 | 9.5 ± 7 g |
| 7 d | 10 | 1 | 30 | 10 ± 2 g |
| 8 d | 10 | 1 | 40 | 20 ± 4 g |
| 9 d | 10 | 1 | 50 | 18 ± 7 g |
| 10 d | 10 | 1 | 80 | 27 ± 8 g |
| 11 d | 10 | 2 | 20 | 10 ± 4 g |
| 12 d | 10 | 2 | 50 | 36 ± 4 g |
| 13 d | 10 | 2 | 80 | 45 ± 5 g |
| 14 d | 10 | 4 | 80 | 50 ± 9 h |
| 15 d | 10 | 8 | 80 | 50 ± 5 h |
| 16 d | 20 | 2 | 80 | 28 ± 5 g |
| 17 d | 30 | 4 | 80 | 30 ± 2 g |
| 18 e | 10 | 8 | 80 | 0 f |
aReaction conditions: [11C]CO2 was bubbled in a solution of 1 (32 μmol, 1 equiv.), DBU (0.05–30 equiv.) in MeCN (160 μL) at room temperature. Then, the reaction mixture was heated (20–80 °C) for 30 seconds. Mitsunobu reagents (1–8 equiv.) in MeCN (100 μL) were added and stirred for 10 s. A (8 equiv. of a 0.5 M solution in THF) was added and quenching after 1 min.
bRCY determined by radio-HPLC not decay-corrected.
c138.5 μmol of 1.
d32 μmol of 1.
e32 μmol of 1 in DMF.
f N = 1.
g N = 2.
h N = 3.