Table 1.
Screening of the catalyst and solvent for the reaction of benzaldehydes and dimedone catalyzed by Zr(HSO4)4.a
 | ||||
|---|---|---|---|---|
| Entry | Catalyst (mol%) | Solvent/condition | Time (min) | Yieldb (%) |
| 1 | 20 | water/reflux | 120 | trace |
| 2 | 20 | THF/reflux | 120 | trace |
| 3 | 20 | CHCl3/reflux | 120 | 20 |
| 4 | 20 | CH3CN/reflux | 120 | 15 |
| 5 | 20 | CH3CH2OH/reflux | 100 | 55 |
| 6 | 10 | solvent-free | 100 | 68 |
| 7 | 20 | solvent-free | 40 | 86 |
| 8 | 30 | solvent-free | 40 | 75 |
| 9 | 0 | solvent-free | 40 | trace |
a
Reaction condition: dimedone (2 mmol), aldehyde (1 mmol) and Zr(HSO4)4 as catalyst.
b
Isolated yield.