Table 4 Optimization of the reaction conditions
Entry | Catalyst (mmol) | Temp. (°C) | Solvent | Yield (%) |
|---|---|---|---|---|
1 | 0.25 | 60 | – | 89 |
2 | 0.50 | 60 | – | 90 |
3 | 0.75 | 60 | – | 91 |
4 | 1.25 | 60 | – | 94 |
5 | 1.50 | 60 | – | 89 |
6 | 1.0 | 50 | – | 95 |
7 | 1.0 | 70 | – | 94 |
8 | 1.0 | 80 | – | 86 |
9 | 1.0 | 90 | – | 79 |
10 | 1.0 | 100 | – | 76 |
11 | 1.0 | Reflux | EtOH | 86 |
12 | 1.0 | Reflux | H2O/EtOH | 76 |
13 | 1.0 | Reflux | H2O | 70 |
14 | 1.0 | Reflux | CH3CN | 65 |
15 | 1.0 | Reflux | CH2Cl2 | 42 |
16 | 1.0 | 60 | – | 96 |