Table 1. Optimization of the Catalytic System for the Oxidation of Styrene by Watera.
| yield
(%) |
|||||
|---|---|---|---|---|---|
| entry | [Ru] | acid (mol %) | conv (%) | 2a | 3a |
| 1 | [Ru]-3 | HOTf (20) | 62 | 39 | 11 |
| 2 | [Ru]-3 | HNTf2 (20) | 74 | 44 | 13 |
| 3 | [Ru]-3 | TsOH·H2O (20) | 71 | 55 | 8 |
| 4 | [Ru]-3 | PhCOOH (20) | 5 | n.d. | 1 |
| 5 | [Ru]-3 | Sc(OTf)3 (20) | 73 | 50 | 8 |
| 6 | [Ru]-3 | In(OTf)3 (20) | 82 | 63 | 7 |
| 7 | [Ru]-3 | none | 9 | n.d. | 5 |
| 8 | [Ru]-2 | In(OTf)3 (20) | 87 | 53 | 28 |
| 9 | [Ru]-1 | In(OTf)3 (20) | 47 | 16 | 2 |
| 10 | [Ru]-3 | In(OTf)3 (40) | 89 | 83 | 4 |
a
Reaction conditions: 1a (0.30 mmol), [Ru] (1.5 mol %), acid, 1,4-dioxane (2.0 mL), water (1.0 mL), heated in a sealed tube at 150 °C (silicon oil bath temperature) at reflux for 36 h. The reaction conversion and yields were determined by GC using mesitylene as the internal standard. n.d. = not detected.