Entry | Catalyst | Solvent | Temperature | Time (min) | Yield (%)a |
1 | without DBSA | H2O | reflux | 240 | trace |
2 | DBSA (25%) | H2O | reflux | 75 | 85 |
3 | DBSA (25%) | EtOH | r.t. | 120 | trace |
4 | DBSA (25%) | EtOH | reflux | 60 | 87 |
5 | DBSA (25%) | MeOH | reflux | 105 | 80 |
6 | DBSA (25%) | EtOH:H2O (1:1) | reflux | 40 | 94 |
7 | DBSA (25%) | MeOH:H2O (1:1) | reflux | 65 | 90 |
8 | DBSA (25%) | EtOH:H2O (1:1) | r.t. | 40 | trace |
9 | DBSA (10%) | EtOH:H2O (1:1) | reflux | 40 | 68 |
10 | DBSA (15%) | EtOH:H2O (1:1) | reflux | 40 | 70 |
11 | DBSA (20%) | EtOH:H2O (1:1) | reflux | 40 | 72 |
12 | DBSA (30%) | EtOH:H2O (1:1) | reflux | 40 | 93 |
13 | DBSA (25%) | EtOH:H2O (1:1) | MV condition | 12 | 95 |