Table 1 Optimization of the reaction conditions
Entry | Catalyst (mmol) | Temp. (°C) | Solvent | Yield (%) |
|---|---|---|---|---|
1 | 0.25 | 70 | – | 87 |
2 | 0.50 | 70 | – | 91 |
3 | 0.75 | 70 | – | 93 |
4 | 1.25 | 70 | – | 90 |
5 | 1.50 | 70 | – | 91 |
6 | 1.0 | 50 | – | 90 |
7 | 1.0 | 60 | – | 89 |
8 | 1.0 | 80 | – | 86 |
9 | 1.0 | 90 | – | 83 |
10 | 1.0 | 100 | – | 76 |
11 | 1.0 | Reflux | EtOH | 85 |
12 | 1.0 | Reflux | H2O/EtOH | 69 |
13 | 1.0 | Reflux | H2O | 52 |
14 | 1.0 | Reflux | n-Hexane | 71 |
15 | 1.0 | Reflux | EtOAc | 82 |
16 | 1.0 | 70 | – | 92 |