Table 2.
Substrate scope investigation of metal-free diastereoselective 1,3-dipolar cycloaddition of N-2,2,2-trifluoroethylisatin ketimines 1a and diverse cyclopentene-1,3-diones 2 [a].
| Entry | 2 (R2/R3) | 3 | dr [b] | Yield (%) [c] |
|---|---|---|---|---|
| 1 | 2b (Me/3-MeC6H4) | 3ab | 84:16 | 96 |
| 2 | 2c (Me/4-MeC6H4) | 3ac | 82:18 | 94 |
| 3 | 2d (Me/3-MeOC6H4) | 3ad | 85:15 | 94 |
| 4 | 2e (Me/4-FC6H4) | 3ae | 88:12 | 96 |
| 5 | 2f (Me/2-ClC6H4) | 3af | 71:29 | 76 |
| 6 | 2g (Me/4-ClC6H4) | 3ag | 86:14 | 94 |
| 7 | 2h (Me/3-BrC6H4) | 3ah | 84:16 | 84 |
| 8 | 2i (Me/4-BrC6H4) | 3ai | 85:15 | 94 |
| 9 | 2j (Me/1-naphthyl) | 3aj | 89:11 | 98 |
| 10 | 2k (Me/2-naphthyl) | 3ak | 86:14 | 99 |
| 11 | 2l (Et/C6H5) | 3al | 88:12 | 69 |
| 12 | 2m (Et/3-BrC6H4) | 3am | 72:28 | 84 |
| 13 | 2n (Et/4-BrC6H4) | 3an | 84:16 | 88 |
[a] The reactions were carried out with 1a (0.15 mmol), 2 (0.10 mmol), and 1.5 equivalents of DABCO in 1.0 mL of DCE at 50 °C for 24 h. [b] Determined by 1H NMR analysis of the crude product. [c] Yield of isolated product as a mixture of diastereoisomers.