Table 2.
Optimization of reaction conditions.a
| entry | toluene/H2O (v/v) | time (h) | yieldb (%) | eec (%) |
| 1 | 1:1 | 5 | 99 | 68 |
| 2 | 1:2 | 5 | 99 | 70 |
| 3 | 1:3 | 3 | 99 | 63 |
| 4 | 1:5 | 1 | 99 | 54 |
| 5 | 2:1 | 5 | 99 | 75 |
| 6 | 3:1 | 36 | 63 | 76 |
| 7d | 2:1 | 40 | 47 | 74 |
| 8e | 2:1 | 7 | 78 | 63 |
| 9f | 2:1 | 4 | 99 | 94 |
| 10g | 2:1 | 4 | 99 | 92 |
aReagents and conditions: catalyst 2 (2 mol %), nitrostyrene (0.5 mmol), and acetylacetone (1 mmol), toluene and water (0.48 mL), rt; bisolated yields; cdetermined by chiral HPLC analysis; dreaction performed at 0 °C; e2.5 mmol acetylacetone used; f5 mol % catalyst 2 used; g10 mol % catalyst 2 used.