Table 3. Results for the Synthesis of Pyrrolidinone-Fused 2,6-Diketopiperazines 7 by a One-Pot Two-Step Sequence.
| entry | 1 (R1) | 4 (R2) | solventa | 7 (%)b | drc |
|---|---|---|---|---|---|
| 1 | 1a (H) | 4a (cC6H11) | MeOH | 7a (78) | – |
| 2 | 1b (Ph) | 4a (cC6H11) | MeOH | 7b (86) | >95:5 |
| 3 | 1c (CH(CH3)2) | 4a (cC6H11) | MeOH | 7c (79) | >95:5 |
| 4 | 1c (CH(CH3)2) | 4a (cC6H11) | ACN | 7c (58) | >95:5 |
| 5 | 1d (CH3) | 4a (cC6H11) | MeOH | 7d (71) | >95:5 |
| 6 | 1d (CH3) | 4a (cC6H11) | ACN | 7d (56) | >95:5 |
| 7 | 1e (CH2Ph) | 4a (cC6H11) | MeOH | 7e (74) | >95:5 |
| 8 | 1b (Ph) | 4b (nC4H9) | MeOH | 7f (75) | >95:5 |
| 9 | 1c (CH(CH3)2) | 4b (nC4H9) | MeOH | 7g (81) | >95:5 |
| 10 | 1e (CH2Ph) | 4b (nC4H9) | MeOH | 7h (69) | >95:5 |
a
Solvent employed in the first stage.
b
Chemical yield after purification.
c
Determined by 1H NMR spectroscopy in the reaction mixture.