Optimization of the synthesis of 1-pyrrolines.
| ||||
|---|---|---|---|---|
| Entrya | Mn salt (equiv.) | Additive (equiv.) | Solvent | Yield (%) |
| 1 | Mn(acac)3 (1.7) | None | CH3CN | 33 |
| 2b | Mn(acac)3 (1.7) | None | CH3CN | Trace |
| 3 | Mn(acac)3 (1.7) | None | DCM | 31 |
| 4 | Mn(acac)3 (1.7) | None | Acetone | 25 |
| 5 | Mn(acac)3 (1.7) | None | DMSO | Trace |
| 6 | Mn(acac)3 (1.7) | None | DMF | Trace |
| 7 | Mn(acac)3 (1.7) | None | TFE | 80 |
| 8 | Mn(acac)3 (1.7) | None | HFIP | 82 |
| 9 | Mn(acac)3 (1.2) | None | HFIP | 83 |
| 10 | Mn(acac)3 (0.9) | None | HFIP | 55 |
| 11 | Mn(OAc)3·2H2O (1.2) | None | HFIP | 36 |
| 12 | MnCl2 (1.2) | None | HFIP | Trace |
| 13 | Mn(acac)2 (1.2) | None | HFIP | 88 |
| 14 | MnCl2 (1.2) | acac (3.6) | HFIP | 80 |
| 15 | MnCl2 (0.2) | acac (3.6) | HFIP | 81 |
| 16c | MnCl2 (0.2) | acac (3.6) | HFIP | 89 |
| 17c | MnCl2 (0.2) | acac (1.0) | HFIP | 89 |
| 18c | MnCl2 (0.2) | acac (0.6) | HFIP | 83 |
| 19c,d | MnCl2 (0.2) | acac (1.0) | HFIP | 91 |
| 20c,e | MnCl2 (0.2) | acac (1.0) | HFIP | 83 |
| 21c,b | MnCl2 (0.2) | acac (1.0) | HFIP | 80 |
| 22c,d | MnCl2 (0.2) | acac (0.6) | HFIP | 82 |
| 23c,d | MnCl2 (0.1) | acac (1.0) | HFIP | 81 |
a
Reaction conditions: 1a (0.45 mmol), 2a (0.3 mmol), AcOH (2.0 equiv.), and Mn salt (as shown) in solvent (2.0 mL), at room temperature (rt) under N2, for 16 h.
b
Without AcOH.
c
0.067 M reaction.
d
1.0 equiv. AcOH.
e
0.5 equiv. AcOH. acac = acetylacetone.