Table 1. Optimization of Reaction Conditions for Hydrolysis of 12 to 14.
entry | solventa | time (h) | temperature | molar ratio 14/15/13b |
---|---|---|---|---|
1 | 0.2 M NaOH | 0.5 | r.t. | 1:0.46:0.16 |
2 | 0.2 M NaOH | 24 | r.t. | 1:0.30:0.02 |
3 | 0.2 M NaOH | 168 | r.t. | 1:0.27:0 |
4 | 1 M NaOH | 0.5 | r.t. | 1:0.20:0.12 |
5 | 1 M NaOH | 24 | r.t. | 1:0.12:0.04 |
6 | 3 M NaOH | 0.5 | r.t. | 1:0.16:0.10 |
7 | 3 M NaOH | 24 | r.t. | 1:0.13:0.04 |
8 | 3 M NaOH | 72 | r.t. | 1:0.10:0.04 |
9 | 3 M NaOH | 168 | r.t. | 1:0.20:0 |
10 | 3 M NaOH | 0.5 | 100 °C | 1:0.16:0.06 |
11 | 3 M HCl | 0.5 | r.t. | NRc |
12 | 3 M HCl | 24 | r.t. | NRc |
13 | 3 M HCl | 3 | 100 °C | 0.07:1:0 |
Reaction conditions: 12 (1.0 mmol), 1,4-dioxane (5 mL), solvent (5 mL), time (0.5–168 h), temperature (room temperature (r.t.) or reflux (100 °C)).
Calculated by NMR analysis.
NR: no reaction occurred, only 12 detected.