Table 2.
Determination of the optimized reaction conditions for the synthesis of compounds 5a
| Entry | Catalyst | Solvent | Temperature (oC) | Time (min) | Yield %a, b |
|---|---|---|---|---|---|
| 1 | -c | EtOH | r.t | 120 | Trace |
| 2 | PS-Cl (10 mg) | EtOH | r.t | 120 | Trace |
| 3 | MPS (10 mg) | EtOH | r.t | 20 | Trace |
| 4 | L-Glu (10 mol%) | EtOH | r.t | 20 | 85 |
| 5 | Ala (10 mol%) | EtOH | r.t | 20 | 69 |
| 6 | Gly (10 mol%) | EtOH | r.t | 20 | 67 |
| 7 | Pro (10 mol%) | EtOH | r.t | 20 | 78 |
| 8 | Ser (10 mol%) | EtOH | r.t | 20 | 65 |
| 9 | L-Glu-MPS (10 mg) | EtOH | r.t | 20 | 75 |
| 10 | L-Glu-MPS (5 mg) | EtOH | r.t | 20 | 82 |
| 11 | L-Glu-MPS (15 mg) | EtOH | r.t | 20 | 89 |
| 12 | L-Glu-MPS (20mg) | EtOH | r.t | 20 | 98 |
| 13 | L-Glu-MPS (25 mg) | EtOH | r.t | 20 | 98 |
| 14 | L-Glu-MPS (20 mg) | MeOH | r.t | 20 | 73 |
| 15 | L-Glu-MPS (20 mg) | H2O | r.t | 20 | 67 |
| 16 | L-Glu-MPS (20 mg) | EtOH: H2O | r.t | 20 | 82 |
| 17 | L-Glu-MPS (20 mg) | DMF | r.t | 20 | 81 |
| 18 | L-Glu-MPS (20 mg) | CH2Cl2 | r.t | 20 | 52 |
| 19 | L-Glu-MPS (20 mg) | EtOH | 40 | 20 | 98 |
| 20 | L-Glu-MPS (20 mg) | EtOH | Reflux | 20 | 98 |
Reaction conditions: 4-chlorobenzaldehyde (1 mmol), dimedone (1 mmol), and ethyl acetoacetate (1 mmol) in the presence of the L-Glu-MPS catalyst in a 10 mL solvent
b Isolated yields. c Catalyst-free conditions